Pharmacokinetics of once-daily dosing of gentamicin in neonates

Confirming the Suitability of a Gentamicin Dosing Strategy in Neonates Using the Population Pharmacokinetic Approach with Truncated Sampling Duration

(1) Background: Gentamicin is known to be nephrotoxic and ototoxic. Although gentamicin dosage guidelines have been established for preterm and term neonates, reports do show attainment of recommended peak concentrations but toxic gentamicin concentrations are common in this age group. (2) Methods: This was a prospective, observational study conducted in Namibia with 52 neonates. A dose of 5 mg/kg gentamicin was administered over 3-5 s every 24 h in combination with benzylpenicillin 100,000 IU/kg/12 h or ampicillin 50 mg/kg/8 h. Two blood samples were collected from each participant using a truncated pharmacokinetic sampling schedule. (3) Results: The one-compartment linear pharmacokinetic model best described the data. Birthweight, postnatal age, and white blood cell count were predictive of clearance (CL), while birthweight was predictive of volume (V). For the typical neonate (median weight 1.57 kg, median postnatal age 4 days (0.011 years), median log-transformed WBC of 2.39), predicted CL and V were 0.069 L/h and 0.417 L, respectively-similar to literature values. Simulated gentamicin concentrations varied with respect to postnatal age and bodyweight. (4) Conclusions: A 5 mg/kg/24 h dosage regimen yielded simulated gentamicin concentrations with respect to age and birthweight similar to those previously reported in the literature to be safe and efficacious, confirming its appropriateness.

Neonatal sepsis: a systematic review of core outcomes from randomised clinical trials

BACKGROUND

The lack of a consensus definition of neonatal sepsis and a core outcome set (COS) proves a substantial impediment to research that influences policy and practice relevant to key stakeholders, patients and parents.

METHODS

A systematic review of the literature was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. In the included studies, the described outcomes were extracted in accordance with the provisions of the Core Outcome Measures in Effectiveness Trials (COMET) handbook and registered.

RESULTS

Among 884 abstracts identified, 90 randomised controlled trials (RCTs) were included in this review. Only 30 manuscripts explicitly stated the primary and/or secondary outcomes. A total of 88 distinct outcomes were recorded across all 90 studies included. These were then assigned to seven different domains in line with the taxonomy for classification proposed by the COMET initiative. The most frequently reported outcome was survival with 74% (n = 67) of the studies reporting an outcome within this domain.

CONCLUSIONS

This systematic review constitutes one of the initial phases in the protocol for developing a COS in neonatal sepsis. The paucity of standardised outcome reporting in neonatal sepsis hinders comparison and synthesis of data. The final phase will involve a Delphi Survey to generate a COS in neonatal sepsis by consensus recommendation.

IMPACT

This systematic review identified a wide variation of outcomes reported among published RCTs on the management of neonatal sepsis. The paucity of standardised outcome reporting hinders comparison and synthesis of data and future meta-analyses with conclusive recommendations on the management of neonatal sepsis are unlikely. The final phase will involve a Delphi Survey to determine a COS by consensus recommendation with input from all relevant stakeholders.

Simplified Dosing Regimens for Gentamicin in Neonatal Sepsis

Background: The effectiveness of antibiotics for the treatment of severe bacterial infections in newborns in resource-limited settings has been determined by empirical evidence. However, such an approach does not warrant optimal exposure to antibiotic agents, which are known to show different disposition characteristics in this population. Here we evaluate the rationale for a simplified regimen of gentamicin taking into account the effect of body size and organ maturation on pharmacokinetics. The analysis is supported by efficacy data from a series of clinical trials in this population.

Methods: A previously published pharmacokinetic model was used to simulate gentamicin concentration vs. time profiles in a virtual cohort of neonates. Model predictive performance was assessed by supplementary external validation procedures using therapeutic drug monitoring data collected in neonates and young infants with or without sepsis. Subsequently, clinical trial simulations were performed to characterize the exposure to intra-muscular gentamicin after a q.d. regimen. The selection of a simplified regimen was based on peak and trough drug levels during the course of treatment.

Results: In contrast to current World Health Organization guidelines, which recommend gentamicin doses between 5 and 7.5 mg/kg, our analysis shows that gentamicin can be used as a fixed dose regimen according to three weight-bands: 10 mg for patients with body weight <2.5 kg, 16 mg for patients with body weight between 2.5 and 4 kg, and 30 mg for those with body weight >4 kg.

Conclusion: The choice of the dose of an antibiotic must be supported by a strong scientific rationale, taking into account the differences in drug disposition in the target patient population. Our analysis reveals that a simplified regimen is feasible and could be used in resource-limited settings for the treatment of sepsis in neonates and young infants with sepsis aged 0–59 days.

Optimizing gentamicin conventional and extended interval dosing in neonates using Monte Carlo simulation - a retrospective study

BACKGROUND

Although aminoglycosides are routinely used in neonates, controversy exists regarding empiric dosing regimens. The objectives were to determine gentamicin pharmacokinetics in neonates, and develop initial mg/kg dosing recommendations that optimized target peak and trough concentration attainment for conventional and extended-interval dosing (EID) regimens.

METHODS

Patient demographics and steady-state gentamicin concentration data were retrospectively collected for 60 neonates with no renal impairment admitted to a level III neonatal intensive care unit. Mean pharmacokinetics were calculated and multiple linear regression was performed to determine significant covariates of clearance (L/h) and volume of distribution (L). Classification and regression tree (CART) analysis identified breakpoints for significant covariates. Monte Carlo Simulation (MCS) was used to determine optimal dosing recommendations for each CART-identified sub-group.

RESULTS

Gentamicin clearance and volume of distribution were significantly associated with weight at gentamicin initiation. CART-identified breakpoints for weight at gentamicin initiation were: ≤ 850 g, 851-1200 g, and > 1200 g. MCS identified that a conventional dose of gentamicin 3.5 mg/kg given every 48 h or an EID of 8-9 mg/kg administered every 72 h in neonates weighing ≤ 850 g, and every 24 and 48 h, respectively, in neonates weighing 851-1200 g, provided the best probability of attaining conventional (peak: 5-10 mg/L and trough: ≤ 2 mg/L) and EID targets (peak:12-20 mg/L, trough:≤ 0.5 mg/L). Insufficient sample size in the > 1200 g neonatal group precluded further investigation of this weight category.

CONCLUSIONS

This study provides initial gentamicin dosing recommendations that optimize target attainment for conventional and EID regimens in neonates weighing ≤ 1200 g. Prospective validation and empiric dose optimization for neonates > 1200 g is needed.

Pain Sensitization, Breastfeeding Effectiveness, and Parental Preferences by Antibiotic Route in Suspected Neonatal Sepsis

OBJECTIVES

Intravenous (IV) and intramuscular (IM) antibiotics have comparable efficacy in treating neonates undergoing sepsis evaluations. There are no clinical data favoring the use of either route regarding newborn pain and parental preferences. We hypothesized that pain associated with IM injections would worsen breastfeeding effectiveness and decrease parental satisfaction, making IV catheters the preferred route.

METHODS

This prospective cohort study took place in an academic institution with nurseries in 2 separate hospitals, 1 providing IV antibiotics, and the other, IM antibiotics. Newborns receiving 48 hours of antibiotics were compared by using objective pain and breastfeeding scores and parental surveys.

RESULTS

In 185 newborns studied, pain scores on a 7-point scale were up to 3.4 points higher in the IM compared with the IV group (P < .001). Slopes of repeated pain scores were 0.42 ± 0.08 and -0.01 ± 0.11 in the IM and IV groups, respectively (P = .002). Breastfeeding scores were similar between groups. Parents in the IV group were less likely to perceive discomfort with antibiotic administration (odds ratio [OR] 0.22; 95% confidence interval [CI] 0.06-0.74) but more likely to perceive interference with breastfeeding (OR 26; 95% CI 6.4-108) and bonding (OR 101; 95% CI 17-590) and more likely to prefer changing to the alternate route (OR 6.9; 95% CI 2.3-20).

CONCLUSIONS

IM antibiotics in newborns are associated with pain sensitization and greater pain than IV dosing. Despite accurately recognizing newborn pain with the IM route, parents preferred this to the IV route, which was perceived to interfere with breastfeeding and bonding.

One dose per day compared to multiple doses per day of gentamicin for treatment of suspected or proven sepsis in neonates

BACKGROUND

Animal studies and trials in older children and adults suggest that a 'one dose per day' regimen of gentamicin is superior to a 'multiple doses per day' regimen.

OBJECTIVES

To compare the efficacy and safety of one dose per day compared to multiple doses per day of gentamicin in suspected or proven sepsis in neonates.

SEARCH METHODS

Eligible studies were identified by searching the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 3) in the Cochrane Library (searched 8 April 2016), MEDLINE (1966 to 8 April 2016), Embase (1980 to 8 April 2016), and CINAHL (December 1982 to 8 April 2016).

SELECTION CRITERIA

All randomised or quasi-randomised controlled trials comparing one dose per day ('once a day') compared to multiple doses per day ('multiple doses a day') of gentamicin to newborn infants.

DATA COLLECTION AND ANALYSIS

Data collection and analysis was performed according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Eleven RCTs were included (N = 574) and 28 excluded. All except one study enrolled infants of more than 32 weeks' gestation. Limited information suggested that infants in both 'once a day' as well as 'multiple doses a day' regimens showed adequate clearance of sepsis (typical RR 1.00, 95% CI 0.84 to 1.19; typical RD 0.00, 95% CI -0.19 to 0.19; 3 trials; N = 37). 'Once a day' gentamicin regimen was associated with fewer failures to attain peak level of at least 5 µg/ml (typical RR 0.22, 95% CI 0.11 to 0.47; typical RD -0.13, 95% CI -0.19 to -0.08; number needed to treat for an additional beneficial outcome (NNTB) = 8; 9 trials; N = 422); and fewer failures to achieve trough levels of 2 µg/ml or less (typical RR 0.38, 95% CI 0.27 to 0.55; typical RD -0.22, 95% CI -0.29 to -0.15; NNTB = 4; 11 trials; N = 503). 'Once a day' gentamicin achieved higher peak levels (MD 2.58, 95% CI 2.26 to 2.89; 10 trials; N = 440) and lower trough levels (MD -0.57, 95% CI -0.69 to -0.44; 10 trials; N = 440) than 'multiple doses a day' regimen. There was no significant difference in ototoxicity between two groups (typical RR 1.69, 95% CI 0.18 to 16.25; typical RD 0.01, 95% CI -0.04 to 0.05; 5 trials; N = 214). Nephrotoxicity was not noted with either of the treatment regimens. Overall, the quality of evidence was considered to be moderate on GRADE analysis, given the small sample size and unclear/high risk of bias in some of the domains in a few of the included studies.

AUTHORS' CONCLUSIONS

There is insufficient evidence from the currently available RCTs to conclude whether a 'once a day' or a 'multiple doses a day' regimen of gentamicin is superior in treating proven neonatal sepsis. However, data suggest that pharmacokinetic properties of a 'once a day' gentamicin regimen are superior to a 'multiple doses a day' regimen in that it achieves higher peak levels while avoiding toxic trough levels. There was no change in nephrotoxicity or auditory toxicity. Based on the assessment of pharmacokinetics, a 'once a day regimen' may be superior in treating sepsis in neonates of more than 32 weeks' gestation.

Feasibility and efficacy of gentamicin for treating neonatal sepsis in community-based settings: a systematic review

BACKGROUND

Neonatal sepsis is a leading cause of neonatal deaths in developing countries. The current recommended in-hospital treatment is parenteral ampicillin (or penicillin) and gentamicin in young infants for 10- 14 days; however, very few could access and afford. The current review is to evaluate the feasibility of gentamicin in community based settings.

METHODS

Both observational and randomized controlled trials were included. Medline, Embase, Cochrane Central Register of Controlled Trials and Central Trial Register of India were searched until September 2013. We assessed the risk of bias by Cochrane Collaboration's "risk of bias" tool.

RESULTS

Two observational studies indicated feasibility ensuring coverage of population, decrease in case fatality rate in the group treated by community health workers. In an RCT, no significant difference was observed in the treatment failure rates [odds ratio (OR)=0.88], and the mortality in the first and second week (OR=1.53; OR=2.24) between gentamicin and ceftriaxone groups. Within the gentamicin group, the combination of penicillin and gentamicin showed a lower rate of treatment failure (OR=0.44) and mortality at second week of life (OR=0.17) as compared to the combination of gentamicin and oral cotrimoxazole.

CONCLUSION

Gentamicin for the treatment of neonatal sepsis is both feasible and effective in community-based settings and can be used as an alternative to the hospitalbased care in resource compromised settings. But there was less evidence in the management of neonatal sepsis in hospitals as was seen in this review in which we included only one RCT and three observational studies.

Extended-interval gentamicin administration in neonates: a simplified approach

OBJECTIVE

Gentamicin dosing is highly variable and remains complicated in the neonatal population. Traditional dosing in our unit resulted in an excessive number of elevated trough serum gentamicin levels. We hypothesized that one uniform gentamicin dose for neonates of all gestational ages will reduce the incidence of elevated trough levels from 50 to 10%.

STUDY DESIGN

Our prospective, randomized, controlled trial enrolled eligible neonates into two groups, according to gestational age (⩽34 6/7 (group I) and >35 0/7 weeks (group II)). Patients in the study arm received a dose of gentamicin 5 mg kg(-1) intravenous (i.v.) every 36 h, whereas patients in the control arm received traditional dosage. Patients were monitored for resolution of infection, serum gentamicin levels and adverse effects. We confirmed our findings in a follow-up study. Fisher's exact and Mann-Whitney tests were used for statistical analysis.

RESULTS

We enrolled 96 neonates, 50 in group I (n=25 per arm) and 46 in group II (n=23 per arm). Elevated trough levels were reduced by 66% in group I (P=0.61) and 100% in group II (P=0.0015). In the study arm of both groups, 48/49 neonates had Cmin serum gentamicin concentration (SGC) <2 mg l(-1) and the majority had a trough SGC <1 mg l(-1) (P<0.0001). The study dose resulted in maximum gentamicin levels in the goal range and a 50% reduction in dosage modifications. There were no treatment failures or adverse effects. Our follow-up study phase confirmed these results.

CONCLUSION

A standardized gentamicin dosage of 5 mg kg(-1) i.v. every 36 h to neonates of all gestational ages was safe and resulted in SGCs in goal therapeutic ranges. The implications of this simplified gentamicin dosage are to reduce health-care costs by less frequent dosing of gentamicin and reducing medication errors in physician prescribing from complicated dosing schemes.

Aminoglycoside toxicity in neonates: something to worry about?

Toxicity has limited the use of aminoglycosides and adult studies report high rates of both ototoxicity and nephrotoxicity. Conversely paediatric studies have shown lower rates and extended interval dosing may have reduced toxicity further. We review the animal and human evidence for aminoglycoside toxicity in neonates including mechanisms, measurement and rates of toxicity; and differences between aminoglycosides and dosing regimens. We discuss genetic susceptibility and the impact of other synergistic effects.

Validation of a dosage individualization table for extended-interval gentamicin in neonates

BACKGROUND

Extended-interval aminoglycoside dosing is increasingly used in neonates; however, guidance on how to monitor concentrations and adjust dosages accordingly is limited.

OBJECTIVE

To prospectively validate the use of a 22-hour gentamicin concentration dosing table for the individualization of extended-interval dosing in the neonatal population by examining the peak and trough concentrations achieved through its use.

METHODS

A prospective observational study was carried out on gentamicin concentrations achieved using a 22-hour post-first-dose gentamicin concentration dosing table for determining dosing intervals in neonates. Neonates (N = 104) in the first week of life, gestational age 23 weeks to full term, in level II and III neonatal intensive care units were included. Neonates were given gentamicin 5 mg/kg intravenously; a table using 22-hour post-first-dose gentamicin concentrations was then used to individualize dosing intervals. Pre- and post-serum gentamicin concentrations on the dosing interval indicated were measured with the second or third doses and used to calculate the peak and trough concentrations achieved.

RESULTS

Use of the 22-hour post-first-dose gentamicin concentration dosing table resulted in dosing intervals that provided appropriate peak (mean 10.55 mg/L) and trough (mean 0.75 mg/L) concentrations (with second or third doses) in all neonates. All patients had trough concentrations less than 2 mg/L, and 73% had a trough concentration less than 1 mg/L. No peak concentrations were less than 5 mg/L, 82% of patients had a peak concentration from 5 to 12 mg/L, and the remaining 18% had concentrations from 12.1 to 16 mg/L. Peak and trough concentrations were similar across all gestational ages.

CONCLUSIONS

Use of a 22-hour post-first-dose gentamicin concentration dosing table to individualize extended-interval gentamicin dosages in neonates resulted in appropriate peak and trough concentrations in all neonates studied. Use of this table will result in appropriate extended-interval aminoglycoside dosages in neonates early in treatment, using a single serum concentration.

Utility of intramuscular antibiotics for secondary prevention of early onset, asymptomatic 'suspected' neonatal sepsis

OBJECTIVE

To evaluate the safety, efficacy and cost-benefit of intramuscular (IM) antibiotics administration in the secondary prevention of suspected neonatal sepsis in asymptomatic term neonates.

STUDY DESIGN

Retrospective review of inborn asymptomatic full-term neonates with birth weights ≥2000 g who required sepsis evaluation and treatment with IM antibiotics were undertaken from July 2001 to July 2008. The IM antibiotic protocol was categorized as inadequate if the neonate became symptomatic, had positive blood or cerebrospinal fluid (CSF) cultures or was readmitted for sepsis within 2 weeks of nursery discharge. Data were analyzed to identify relationships between key indicators for the presence of neonatal bacterial infection, 'inadequate IM antibiotics protocol' and the rehospitalization rates.

RESULT

There were 29 698 infants admitted to the newborn nursery (NBN) during the study period. A total of 5045 infants (17%) were evaluated for suspected neonatal sepsis; 421 neonates (8.3%) were treated with IM antibiotics for 48 to 72 h. Fourteen infants (3.3%) met criteria for 'inadequate IM antibiotics protocol'. Seven infants developed symptoms within the first 32 h of life, and seven infants had positive blood or CSF cultures, one of whom required rehospitalization. None of the infants were hemodynamically unstable or developed complications, including adverse events associated with IM drug administration.

CONCLUSION

Use of IM antibiotics is a safe alternative to intravenous antibiotics in the secondary prevention of asymptomatic term newborns with presumed sepsis. There is a substantial cost savings in caring for asymptomatic neonates with presumed sepsis in the NBN compared with neonatal intensive care unit costs.

One dose per day compared to multiple doses per day of gentamicin for treatment of suspected or proven sepsis in neonates

BACKGROUND

Animal studies and trials in older children and adults suggest that a one dose per day regimen of gentamicin is superior to a multiple doses per day regimen.

OBJECTIVES

To compare the efficacy and safety of one dose per day compared to multiple doses per day of gentamicin in suspected or proven sepsis in neonates.

SEARCH METHODS

Eligible studies were identified by searching the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, April 2011), MEDLINE (1966 to April 2011), EMBASE 1980 to April 2011, and CINAHL (December 1982 to April 2011). Abstracts of the Society for Pediatric Research were searched from 1980 to 2010 inclusive.

SELECTION CRITERIA

All randomised or quasi randomised controlled trials comparing one dose per day ( 'once a day') compared to multiple doses per day ( 'multiple doses a day') of gentamicin to newborn infants < 28 days of life.

DATA COLLECTION AND ANALYSIS

Data collection and analysis was performed according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Eleven studies were included (N = 574) and nineteen excluded. All infants in both 'once a day' as well as 'multiple doses a day' regimen showed adequate clearance of sepsis [typical RD 0.00 (95% CI - 0.19 to 0.19); 3 trials; N = 36]. For the other primary outcome measures relating to gentamicin pharmacokinetics 'once a day' dosing of gentamicin was superior. 'Once a day' gentamicin regimen was associated with less failures to attain peak level of at least 5 µg/ml [typical RR 0.22 (95% CI 0.11 to 0.47); 9 trials; N = 422] and less failures to achieve trough levels of < 2 µg/ml [typical RR 0.38 (95% CI 0.27 to 0.55); 11 trials N = 503] compared to 'multiple doses a day' regimen.Ototoxicity and nephrotoxicity were not noted with either of the treatment regimens.

AUTHORS' CONCLUSIONS

There is insufficient evidence from the currently available RCTs to conclude whether 'once a day' or 'multiple doses a day' regimen of gentamicin is superior in treating proven neonatal sepsis. However, data suggests that pharmacokinetic properties of 'once a day' gentamicin regimen are superior to 'multiple doses a day' regimen in that it achieves higher peak levels while avoiding toxic trough levels. There is no change in nephrotoxicity or auditory toxicity. Based on this assessment of pharmacokinetics, 'once a day regimen' may be superior in treating neonatal sepsis in neonates greater than 32 weeks gestation.

The efficacy and toxicity of two dosing-regimens of amikacin in neonates with sepsis

WHAT IS KNOWN AND OBJECTIVE

Neonatal sepsis is one of the most common reasons for admission to neonatal units in developing countries. Aminoglycosides widely used in its treatment are usually administered two or three times a day. Less frequent doing may be more convenient and as effective. We aim to compare the efficacy and safety (nephrotoxicity) of once daily vs. twice daily dosing of amikacin in neonates with suspected or proven sepsis and report on the drug's pharmacokinetics in these subjects.

METHODS

Thirty neonates of gestational age ≥ 36 weeks and body weight ≥ 2500 g with suspected or proven sepsis were randomized to receive amikacin either at a dose of 15 mg/kg once per day; group I (n = 15), or a dose of 7.5 mg/kg twice per day, group II (n = 15). All neonates received classical treatment of sepsis including antibiotics, hemodynamic support, inotropic support based on blood pressure levels and size of the heart in chest X-ray, if needed. Amikacin was infused over 1 h. Peak and trough serum samples for amikacin were measured for all infants at steady state. Nephrotoxicity was assessed by serum creatinine and urinary N-acetyl β-D-glucosaminidase before and 7 days after therapy. Clinical efficacy was compared using both observation of clinical status and normalization of laboratory tests.

RESULTS

All the patients in group I had achieved a trough level < 10 μg/mL and two patients had trough concentration > 10 μg/mL in group II. No significant difference between group I and group II in either baseline or day 7 serum creatinine was demonstrated (P >0.05). No significant difference was found between the two groups in clinical efficacy or renal toxicity. The calculated pharmacokinetic parameters were in group I and II, respectively: clearance = 63.8 ± 15.9 mL/kg/h and 73.5 ± 18.1 mL/kg/h; volume of distribution = 0.54 ± 0.09 L/kg and 0.61 ± 0.13 L/kg, half-life =6.1 ± 1.0 h and 5.95 ± 1.1 h.

WHAT IS NEW AND CONCLUSION

As expected, amikacin given once every 24 h to septic neonates of ≥ 36 weeks of gestation achieved higher peak levels and lower trough concentrations than the twice daily regimen. Treatment with once daily regimen did not lead to more nephrotoxicity than with a twice-daily regimen, and showed comparable efficacy.

Pharmacokinetic outcomes of a simplified, weight-based, extended-interval gentamicin dosing protocol in critically ill neonates

STUDY OBJECTIVE

To determine the pharmacokinetic outcomes of a simplified, weight-based, extended-interval gentamicin dosing protocol for critically ill neonates.

DESIGN

Retrospective medical record review with pharmacokinetic analysis.

SETTING

Two neonatal intensive care units in a pediatric tertiary care system.

PATIENTS

Sequential sample of 644 critically ill neonates less than 7 days old without evidence of renal dysfunction who received gentamicin, dosed by using a simplified, weight-based, extended-interval dosing protocol, on the first day of life for suspected sepsis between February 2003 and January 2008, and who had subsequent gentamicin plasma concentrations measured during their first week of life.

MEASUREMENTS AND MAIN RESULTS

Data were collected on birth weight, gestational age at birth, serum creatinine concentration during the first 10 days of life, medical conditions, and concomitant drugs. Gentamicin dosing and its pharmacokinetic parameters were noted for each patient. A mean dose of 3.96 mg/kg/dose of gentamicin was administered intravenously every 48 hours in neonates weighing less than 1250 g at birth and every 24 hours in those weighing 1250 g or more. If the neonate received concurrent indomethacin, however, gentamicin was given every 48 hours. Protocol success was defined as a peak gentamicin plasma concentration of 7-10 mg/L and a trough concentration less than 2 mg/L. Mean gentamicin peak and trough concentrations were 9.38 mg/L (95% confidence interval [CI] 9.24-9.52 mg/L) and 1.00 mg/L (95% CI 0.96-1.04 mg/L), respectively. With use of the protocol, 361 neonates (56.1%) achieved gentamicin peak plasma concentrations in the range defined as successful and 610 neonates (94.7%) achieved successful trough concentrations. The mean gentamicin apparent volume of distribution and half-life were 0.48 L/kg (95% CI 0.47-0.49 L/kg) and 8.31 hours (95% CI 8.09-8.52 hrs), respectively.

CONCLUSION

This simplified, weight-based, extended-interval gentamicin dosing protocol for critically ill neonates was effective in achieving therapeutic peak plasma concentrations of gentamicin in most of the patients and, as a high proportion of patients had acceptable trough concentrations, may minimize the potential for toxicity.

Accuracy of Empiric Gentamicin Dosing Guidelines in Neonates

OBJECTIVE

To evaluate the accuracy of a neonatal gentamicin nomogram to achieve therapeutic gentamicin serum concentrations without further adjustment, allowing for decreased serum drug monitoring

METHODS

Retrospective single center review of all gentamicin pharmacokinetic evaluations in patients ≤ 30 days of life from July 2005 – June 2007. Patients were evaluated for postnatal age, gestational age, weight, serum creatinine, dose/interval, serum drug peaks and troughs, results of discharge hearing test and recent use of indomethacin. Logistic regression was utilized to determine potential factors impacting overall dosing accuracy, potentially allowing for decreased therapeutic drug monitoring. Factors found to be significant were incorporated into new guidelines which were evaluated through pharmacokinetic modeling.

RESULTS

Overall accuracy rate was 84% when empiric dosing guidelines were utilized; 16% of all doses were changed due to supratherapeutic troughs and 1% were changed due to subtherapeutic peaks. Variables found to impact the necessity for dose changes incuded gestational age (p≤0.001), weight (p≤0.001), indomethacin use (p≤0.001), number of indomethacin doses used (p≤0.001 and p=0.009 for 1–3 and 4–6 doses, respectively), and SCr in patients ≥ 7 days old (p=0.028); however, only gestational age remained a significant predictor when all other factors were considered (p=0.008). The current guidelines were changed to account for increased troughs in patients ≤ 28 weeks gestation and examined through pharmacokinetic modeling. Pharmacokinetic modeling of the new guidelines predicted an overall accuracy of 94%.

CONCLUSIONS

From the data gathered regarding the accuracy in patients ≥ 35 weeks gestation, we recommend to decrease therapeutic drug monitoring within this cohort. Utilizing the results of regression analysis, the current guidelines have been adjusted to allow for increased clearance in patients ≤ 28 weeks gestation, although they still need to be prospectively evaluated.

Optimizing pediatric dosing: a developmental pharmacologic approach

Many physiologic differences between children and adults can result in age-related differences in pharmacokinetics. Understanding the effects of age on bioavailability, volume of distribution, protein binding, hepatic metabolic isoenzymes, and renal elimination can provide insight into optimizing doses for pediatric patients. We performed a search of English-language literature using the MEDLINE database regarding age and pharmacokinetics (1979-July 2008). We then evaluated the literature with an emphasis on drugs with one primary elimination pathway, such as renal clearance or a pathway involving a single metabolic isoenzyme. Our mechanistic-based analysis revealed that children need weight-corrected doses that are substantially higher than adult doses for drugs that are metabolically eliminated solely by the specific cytochrome P450 (CYP) isoenzymes CYP1A2, CYP2C9, and CYP3A4. In contrast, weight-corrected doses for drugs eliminated by renal excretion or metabolism involving CYP2C19, CYP2D6, N-acetyltransferase 2, or uridine diphosphate glucuronosyltransferases are similar in children and adults. In children, bioavailability of drugs with high first-pass metabolism is decreased for drugs metabolized by CYP1A2, CYP2C9, and CYP3A4. Limited data suggest that by age 5 years, bioavailability of drugs affected by efflux transporters should be equivalent to that of adults. Using a pharmacokinetics-based approach, rational predictions can be made for the effects of age on drugs that undergo similar pathways of elimination, even when specific pharmacokinetic data are limited or unavailable.

Once daily dose gentamicin in neonates - is our dosing correct?

AIM

The aim of this paper is to study the safety and efficacy (measured by therapeutic level) of once daily gentamicin in neonates >or=32 weeks of gestation and <or=7 days of age.

SETTING

Level II neonatal intensive care unit.

SUBJECTS

Neonates >or=32 weeks of gestation and <or=7 days of age treated with gentamicin for presumed sepsis.

METHODS

Gentamicin was administered by intravenous injection at 4 mg/kg/day once daily. Peak and trough gentamicin levels were measured at the third dose.

RESULTS

In neonates with gestational age between 32 and 36 weeks, 14 out of 65 (22%) had trough serum concentration >2 mg/L. Only 39 (60%) had peak and trough levels within the therapeutic range. All babies who had audiometric evaluation (62 out of 65) had normal hearing. Out of the 65 babies, 60 had paired serum creatinine levels estimated and none had evidence of renal dysfunction. Among term neonates, only 2 out of 50 had the trough serum concentration of >2 mg/L. In 38 (76%) of the 50 neonates, the trough serum gentamicin concentration was <2.0 mg/L and the peak level was <10 mg/L. Forty-eight babies had audiometric evaluation which was normal.

CONCLUSION

A dose of 4 mg/kg/day produces serum gentamicin levels outside the therapeutic range in two-fifths of neonates between 32 and 36 +/- 6 weeks. A single dose of 4 mg/kg/day of gentamicin is appropriate for term babies and probably excessive for 32-36 weeks' neonates.

Parenteral antibiotics for the treatment of serious neonatal bacterial infections in developing country settings

BACKGROUND

A number of special issues must be considered when selecting simple, safe, inexpensive, and effective antimicrobial regimens for treatment of neonatal sepsis in developing country community settings.

METHODS

We reviewed available data regarding pharmacologic profiles of parenteral antibiotics with specific attention to properties relevant to their use in the treatment of neonatal infections in developing country communities.

RESULTS

For community-based management of neonatal infections, particularly attractive properties include efficacy and safety of extended-interval, intramuscular dosing regimens. The penicillins and cephalosporins have relatively favorable efficacy and safety profiles. Although the aminoglycosides have narrow therapeutic indices, when used appropriately, they are safe and effective. Although inexpensive and effective, the potential for significant life-threatening toxicity among neonates associated with chloramphenicol makes it the least preferred of the parenteral agents for empiric therapy.

CONCLUSIONS

The preferred parenteral regimens for community and first-level facility use are a combination of procaine penicillin G and gentamicin, or ceftriaxone given alone, which are safe and retain efficacy when dosed at extended intervals (> or =24 hours) by intramuscular administration.

[Comparison of two gentamicin dosing schedules in the newborn]

INTRODUCTION

Gentamicin is widely used in full-term neonates as empirical therapy for early-onset suspected or proven sepsis. Several dosing schedules for gentamicin have been recommended for this neonatal population.

OBJECTIVE

To compare gentamicin serum levels, efficacy and toxicity of two dosing schedules in term and preterm newborns.

MATERIAL AND METHODS

The study included 200 newborns who were started on gentamicin therapy. Group A (N=100) was prescribed a multiple-daily dosing regimen and Group B (N=100) on a once-daily dosing regimen. Newborns in Group A received gentamicin at 2.5-3.5 mg/kg/dose q12-18 h depending on postnatal age and serum creatinine levels, and newborns in Group B received 4-5 mg/kg/dose q24-48 h depending on postconceptional and postnatal age. All peak and trough serum drug levels, demographic data, and markers of potential nephrotoxicity and ototoxicity were compared.

RESULTS

Peak serum gentamicin levels were significantly higher (8.2+/-0.22 microg/ml vs. 5.9+/-0.13 microg/ml; p <or= 0.001) and trough levels were significantly lower (0.9+/-0.06 microg/ml vs. 1.7+/-0.08 microg/ml; p <or= 0.001) in Group B than in Group A. There was no significant difference between the groups either in the clinical failure rate or in the nephrotoxicity or ototoxicity outcomes.

CONCLUSIONS

Once-daily dosing regimen of gentamicin in preterm and term newborns is safe and effective, with a reduced risk of serum drug concentrations falling outside the therapeutic range.

Individualising netilmicin dosing in neonates

PURPOSE

The aim of this study was develop an optimal dosing regimen for netilmicin in neonates.

METHODS

This was a population pharmacokinetic study in 97 neonates aged from 2 to 28 days after the due date who were being treated with netilmicin for suspected sepsis. The model was used to simulate dosing regimens.

RESULTS

The principle factors influencing netilmicin clearance (CL) were postmenstrual age (PMA) and current body weight (CWT), and the principal determinant of volume of distribution (V) was CWT. The final covariate model was CL = 0.192 x (CWT/2)(1.35) x (PMA/40)(1.03), V = 1.5 x (CWT/2)(0.3). The optimal dosing was 5 mg/kg ever 36 h, 5 mg/kg every 24 h, 6 mg/kg every 24 h and 7 mg/kg every 24 h for neonates < or =27, 28-30, 31-33 and > or =34 weeks PMA, respectively.

CONCLUSION

Individualisation of netilmicin dosing in neonates requires adjustment of dose by body weight, and dosing interval by both PMA and CWT.

Determination of extended-interval gentamicin dosing for neonatal patients in developing countries

BACKGROUND

Infectious diseases account for an estimated 36% of neonatal deaths globally. The purpose of this study was to determine safe, effective, simplified dosing regimens of gentamicin for treatment of neonatal sepsis in developing countries.

METHODS

Neonates with suspected sepsis in the neonatal intensive care unit (NICU) at Christian Medical College and Hospital (CMC), Vellore, India (n = 49), and Dhaka Shishu Hospital (DSH), Bangladesh (n = 59), were administered gentamicin intravenously according to the following regimens: (1) 10 mg every 48 hours for neonates <2000 g; (2) 10 mg every 24 hours for neonates 2000-2249 g; and (3) 13.5 mg every 24 hours for neonates > or =2500 g. Serum gentamicin concentration (SGC) at steady state and pharmacokinetic indices were determined. Renal function was followed while under treatment and hearing was examined 6 weeks to 3 months after discharge.

RESULTS

All neonates, except 1 weighing 2000-2249 g at DSH, had a peak SGC >4 microg/mL. Overall, 5 (10%) and 17 (29%) infants had a peak SGC level > or =12 microg/mL from CMC and DSH, respectively, and 10 (20%) and 4 (7%) cases from CMC and DSH, respectively, had a trough SGC level > or =2 microg/mL. However, no infant <2000 g had a trough SGC level > or =2 microg/mL. We found no evidence of gentamicin nephrotoxicity or ototoxicity.

CONCLUSION

Safe, therapeutic gentamicin dosing regimens were identified for treatment of neonatal sepsis in developing country settings. Administration of these doses could be simplified through use of Uniject, a prefilled, single injection device designed to make injections safe and easy to deliver in developing country settings.

Guidelines on paediatric dosing on the basis of developmental physiology and pharmacokinetic considerations

The approach to paediatric drug dosing needs to be based on the physiological characteristics of the child and the pharmacokinetic parameters of the drug. This review summarises the current knowledge on developmental changes in absorption, distribution, metabolism and excretion and combines this knowledge with in vivo and in vitro pharmacokinetic data that are currently available. In addition, dosage adjustments based on practical problems, such as child-friendly formulations and feeding regimens, disease state, genetic make-up and environmental influences are presented. Modification of a dosage based on absorption, depends on the route of absorption, the physico chemical properties of the drug and the age of the child. For oral drug absorption, a distinction should be made between the very young and children over a few weeks old. In the latter case, it is likely that practical considerations, like appropriate formulations, have much greater relevance to oral drug absorption. The volume of distribution (V(d)) may be altered in children. Hydrophilic drugs with a high V(d) in adults should be normalised to bodyweight in young children (age <2 years), whereas hydrophilic drugs with a low V(d) in adults should be normalised to body surface area (BSA) in these children. For drugs that are metabolised by the liver, the effect of the V(d) becomes apparent in children <2 months of age. In general, only the first dose should be based on the V(d); subsequent doses should be determined by the clearance. Pharmacokinetic studies on renal and liver function clarify that a distinction should be made between maturation and growth of the organs. After the maturation process has finished, the main influences on the clearance of drugs are growth and changes in blood flow of the liver and kidney. Drugs that are primarily metabolised by the liver should be administered with extreme care until the age of 2 months. Modification of dosing should be based on response and on therapeutic drug monitoring. At the age of 2-6 months, a general guideline based on bodyweight may be used. After 6 months of age, BSA is a good marker as a basis for drug dosing. However, even at this age, drugs that are primarily metabolised by cytochrome P450 2D6 and uridine diphosphate glucuronosyltransferase should be normalised to bodyweight. In the first 2 years of life, the renal excretion rate should be determined by markers of renal function, such as serum creatinine and p-aminohippuric acid clearance. A dosage guideline for drugs that are significantly excreted by the kidney should be based on the determination of renal function in first 2 years of life. After maturation, the dose should be normalised to BSA. These guidelines are intended to be used in clinical practice and to form a basis for more research. The integration of these guidelines, and combining them with pharmacodynamic effects, should be considered and could form a basis for further study.

One dose per day compared to multiple doses per day of gentamicin for treatment of suspected or proven sepsis in neonates

BACKGROUND

Gentamicin is widely used in the treatment of suspected or proven neonatal sepsis. Animal studies and systematic reviews from trials in older children and adults suggest that a one dose per day regimen is superior to a multiple doses per day regimen. Pharmacokinetic studies and retrospective audits in neonatal population also favour once a day administration of gentamicin. However, there is no consensus regarding the dose interval regimen in the neonatal population.

OBJECTIVES

To compare the efficacy and safety of one dose per day compared to multiple doses per day of gentamicin in suspected or proven sepsis in neonates.

SEARCH STRATEGY

Eligible studies were identified by searching MEDLINE (March 2005), EMBASE 1980 - 2004, Oxford Database of Perinatal Trials, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2005) and CINAHL (December 1982 - March 2005). Abstracts of the Society for Pediatric Research were hand searched from 1980 to 2004 inclusive. No language restrictions were applied.

SELECTION CRITERIA

All randomised or quasi randomised controlled trials comparing one dose per day ( 'once a day') compared to multiple doses per day ( 'multiple doses a day') of gentamicin to newborn infants < 28 days of life.

DATA COLLECTION AND ANALYSIS

Methodological quality of eligible studies was assessed according to allocation concealment, blinding of intervention, blinding of outcome assessment and completeness of follow up. Data were sought regarding effects on clinical efficacy, pharmacokinetic efficacy, ototoxicity and nephrotoxicity of the two regimens. When appropriate, meta-analysis was conducted to provide a pooled estimate of effect. For categorical data, the typical relative risk (RR), typical risk difference (RD) and number needed to treat (NNT) with 95% confidence intervals (CI) were calculated. Continuous data were analysed using weighted mean difference (WMD).

MAIN RESULTS

Twenty four studies were initially identified. Thirteen were excluded and eleven studies (N = 574) included. All studies compared the effectiveness and safety of 'once a day' versus 'multiple doses a day' regimen of gentamicin in newborn infants. Only one study enrolled infants less than 32 weeks gestation. All except one trial used intravenous infusion. One trial used gentamicin as a bolus dose over one minute. Two trials used intramuscular gentamicin in some of their study infants. For the primary outcome of 'clearance of sepsis', all infants in both 'once a day' as well as 'multiple doses a day' regimen showed adequate clearance of sepsis [Typical RD 0.00 (95% CI - 0.19, 0.19); 3 trials; N = 36]. For the other primary outcome measures relating to gentamicin pharmacokinetics, 'once a day dosing' of gentamicin was superior. 'Once a day' gentamicin regimen is associated with less failures to attain peak level of at least 5 microg/ml [Typical RR 0.22 (95% CI 0.11, 0.47); Typical RD -0.13 (95% CI -0.19, -0.08); 9 trials; N = 422]; less failures to achieve trough levels of < 2 microg/ml [Typical RR 0.38 (95% CI 0.27, 0.55); Typical RD -0.22 (95% CI -0.29, -0.15); 11 trials N = 503]; higher peak levels [WMD 2.58 (95% CI 2.26, 2.89); 10 trials; N = 440] and lower trough levels [WMD -0.57 (95% CI -0.69, -0.44); 10 trials; N = 440] compared to 'multiple doses a day' regimen. Ototoxicity and nephrotoxicity were not noted with either of the treatment regimens. Significant heterogeneity was noted for some of the outcomes measured. Hence the results need to be interpreted with caution. Possible reasons for heterogeneity are different gestational ages of study infants and the timing of collection of blood samples in relation to a particular dose and the day of therapy on which the samples were collected.

AUTHORS' CONCLUSIONS

There is insufficient evidence from the currently available RCTs to conclude whether 'once a day' or 'multiple doses a day' regimen of gentamicin is superior in treating proven neonatal sepsis. However data suggests that pharmacokinetic properties of 'once a day' gentamicin regimen are superior to 'multiple doses a day' regimen in that it achieves higher peak levels while avoiding toxic trough levels. There is no change in nephrotoxicity or auditory toxicity. Based on this assessment of pharmacokinetics, 'once a day regimen' may be superior in treating neonatal sepsis in neonates more than 32 weeks gestation.

Aminoglycoside extended interval dosing in neonates is safe and effective: a meta-analysis

OBJECTIVES

To review the evidence from controlled clinical trials of neonates given equal daily aminoglycoside doses as extended interval dosing (dosage interval typically 24 hours in term and 36-48 hours in immature neonates) compared with traditional dosing (dosage interval typically 8-12 hours in term and 12-24 hours in immature neonates).

DESIGN

Systematic review and meta-analysis of controlled trials found in electronic databases, trial registers, and references in reviews and selected trials.

SETTINGS

The selected trials were blinded and assessed for methodological quality. Each trial's own predefined criteria for treatment failure, nephrotoxicity, ototoxicity, and therapeutic serum drug concentrations were used.

SUBJECTS

Controlled trials of neonatal aminoglycoside treatment in which equal aminoglycoside daily doses were given at traditional and extended dosage intervals.

MAIN OUTCOME MEASURES

Serum drug concentrations outside the therapeutic range. Treatment failure and toxicity.

RESULTS

Sixteen trials involving 823 neonates met the inclusion criteria for the systematic review. Twelve trials involving 698 neonates were included in the meta-analysis of the pharmacokinetics. Compared with traditional dosing, extended interval dosing was associated with a significantly lower risk of both peak (summary risk ratio 0.50, 95% confidence interval 0.26 to 0.94) and trough (0.36, 0.25 to 0.56) serum drug concentrations outside the therapeutic range. Accurate information on treatment failure was obtained in nine trials involving 555 neonates. One trial reported treatment failure. In this trial two neonates in the traditional dosing group did not respond to treatment within 72 hours. Nephrotoxicity was investigated in 589 neonates in 12 trials and ototoxicity in 210 neonates in four trials, with no significant differences between the two dosing regimens.

CONCLUSIONS

Extended interval dosing of aminoglycosides in neonates is safe and effective, with a reduced risk of serum drug concentrations outside the therapeutic range.

Gentamicin usage in newborns--a simple and practical regime

OBJECTIVE

To audit the gentamicin usage guidelines due to concerns that it resulted in too many sub-therapeutic peak levels, devise a new guideline and re-audit after change in practise.

METHOD

A prospective audit of 50 sets of gentamicin levels on the Old Gentamicin Regime was conducted. Desired levels were a trough <2 microg/ml and peak between 5-10 microg/ml. These were taken just before and one hour after the third dose respectively. Peak levels were found to be in the sub-therapeutic range in the majority on this regime. Therefore the New Gentamicin Regime was put into practise. A re-audit was conducted of the new gentamicin regime and 60 trough levels were taken. Peak levels were taken in only 20 newborns with the intention of not doing peak levels routinely if these were satisfactory and the data were analysed.

RESULTS

Although trough levels were satisfactory in 98% (49/50), peak levels were sub-therapeutic in 92% (46/50) on the old gentamicin regime. Following change in practise to the new gentamicin regime trough levels were satisfactory in 96.6% (58/60). We collected 20 peak levels and these were satisfactory in 80% (16/20).

CONCLUSIONS

The new gentamicin usage guideline achieves peak levels in the therapeutic range in the majority without any added risk of toxic trough levels. Peak levels need not be done routinely in all newborns on the new regime.

The effect of sepsis upon gentamicin pharmacokinetics in neonates

AIM

To investigate the effect of sepsis upon the volume of distribution (Vd) of gentamicin in neonates.

METHODS

A retrospective chart review was conducted of neonates admitted to Dunedin Hospital who had gentamicin concentrations performed between 1st January 2000 and 30th October 2003. Data from 277 neonates, including a total of 576 gentamicin concentrations, were included in the pharmacokinetic analysis. Fifteen (5.4%) of the neonates had confirmed sepsis. Pharmacokinetic analyses were performed with NONMEM using a one compartment first order elimination model. Duration of infusion (D) was included as a parameter in the model. Covariates included sepsis (SEP), chronological age, gestational age (GA), birth weight, current weight, gender, Apgar score at 1 (AP1) and 5 (AP2) minutes, plasma C-reactive protein and serum creatinine.

RESULTS

The initial model provided a mean estimates of clearance (CL) of 0.0460 l kg(-1) h(-1), volume of distribution (Vd) of 0.483 l kg(-1) and D of 0.748 h. The magnitudes of interpatient variability, expressed as CV%, were 29.2% for CL, 20.8% for Vd and 71.5% for D. The magnitude of residual variability in gentamicin concentrations was 88.0%. The final pharmacokinetic model was: CL = (0.0177 + 0.00147.(GA-20) + 0.000635.AP2) l kg(-1) h(-1), Vd = (0.483 +0.0656. sepsis) l kg(-1), D = 0.672 h. The interpatient variability (CV%) was 22.8% for CL, 22.8% for Vd and 97.7% for D. The magnitude of residual variability in gentamicin concentrations was 83.3%.

CONCLUSIONS

The 14% increase in Vd in septic neonates implies that larger doses may be required to achieve peak therapeutic concentrations in the presence of sepsis. D is an important parameter in neonatal pharmacokinetic models.

Validation of a simplified netilmicin dosage regimen in infants

The aim of this study was to validate a simplified high-dosage, extended-interval netilmicin dosage regimen for infants. A total of 129 infants receiving 163 treatment courses of netilmicin (6 mg kg every 24 or 36 h depending on gestational age (GA), postnatal age and postmenstrual age) was analysed. Serum netilmicin concentrations were monitored before (Cmin), 30 min (C0.5h) after and 7.5 h (C7.5h) after the third dose. In 110 patients during first week of life mean C0.5h was 10.5 mg/l. Mean C0.5h was significantly lower (9.0 mg/l) in 38 infants older than 1 week of age. 14 of 15 patients with Cmin levels > or = 2 mg/l receiving netilmicin every 36 h were < 28 weeks of gestation. In the first week of life significant correlations between GA and elimination half-life (p < 0.001) and between plasma creatinine and elevated Cmin (p < 0.002) were found, but no correlation between C0.5h and GA. In this high-dosage regimen a dosing interval of 48 h for GA < 29 weeks, 36 h for GA 29-36 weeks and 24 h for full term babies seems appropriate, during first week of life, to avoid the majority of elevated trough levels and still obtain maximal therapeutic efficacy.

Drug dosing during intermittent hemodialysis and continuous renal replacement therapy : special considerations in pediatric patients

Chronic renal failure is, fortunately, an unusual occurrence in children; however, many children with various underlying illnesses develop acute renal failure, and transiently require renal replacement therapy - peritoneal dialysis, intermittent hemodialysis (IHD), or continuous renal replacement therapy (CRRT). As children with acute and chronic renal failure often have multiple comorbid conditions requiring drug therapy, generalists, intensivists, nephrologists, and pharmacists need to be aware of the issues surrounding the management of drug therapy in pediatric patients undergoing renal replacement therapy. This article summarizes the pharmacokinetics and dosing of many drugs commonly prescribed for pediatric patients, and focuses on the management of drug therapy in pediatric patients undergoing IHD and CRRT in the intensive care unit setting. Peritoneal dialysis is not considered in this review. Finally, a summary table with recommended initial dosages for drugs commonly encountered in pediatric patients requiring IHD or CRRT is presented.

Extended-interval aminoglycoside administration for children: a meta-analysis

BACKGROUND

There has been a long-standing debate regarding whether aminoglycosides should be administered on a multiple daily dosing (MDD) or once-daily dosing (ODD) schedule. Several unique characteristics of the aminoglycosides make ODD an attractive and possibly superior alternative to MDD. These include concentration-dependent bactericidal activity; postantibiotic effect, which allows continued efficacy even when serum concentrations fall below expected minimum inhibitory concentrations; decreased risk of adaptive resistance; and diminished accumulation in renal tubules and inner ear.

OBJECTIVE

To assess the relative efficacy and toxicity of ODD, compared with MDD, of aminoglycosides among pediatric patients.

STUDY SELECTION

Randomized, controlled trials among children, evaluating the relative efficacy and toxicity of ODD versus MDD of aminoglycosides, with similar total daily doses in the compared arms, were selected.

DATA SOURCES

PubMed (1966-2003) and Embase (1982-2003) databases, the Cochrane Controlled Trials Registry (2003), and references of eligible studies and pediatric review articles were searched.

DATA EXTRACTION

Study population characteristics and outcome data were extracted independently in duplicate, and consensus was reached on all items. The following outcome data were considered: (1) clinical or microbiologic failure, as defined in each study; (2) clinical failure; (3) microbiologic failure; (4) primary nephrotoxicity, ie, any rise in serum creatinine or decrease in creatinine clearance with thresholds as defined in each study; (5) secondary nephrotoxicity, ie, urinary excretion of proteins or phospholipids; and (6) ototoxicity based on pure tone audiometry, brainstem auditory evoked responses, or otoacoustic emissions for neonates and infants, vestibular testing, clinical impression, or any other method. All of the efficacy and toxicity outcomes were evaluated at the end of therapy.

RESULTS

Identification of eligible studies and study characteristics: 24 eligible studies published between 1991 and 2003 were identified. Aminoglycosides were used in different clinical settings (neonatal intensive care unit: 6 studies; cystic fibrosis: 3 studies; cancer: 5 studies; urinary tract infections: 4 studies; diverse infectious indications: 5 studies; pediatric intensive care unit: 1 study). Aminoglycosides used included amikacin (9 studies), gentamicin (11 studies), tobramycin (2 studies), netilmicin (2 studies), and tobramycin or netilmicin (1 study).

EFFICACY

There was no significant difference between ODD and MDD in the clinical failure rate, microbiologic failure rate, and combined clinical or microbiologic failure rates, but trends favored ODD consistently. There was no between-study heterogeneity for any outcome. Efficacy analysis of all trials indicating either clinical or microbiologic failures demonstrated pooled failure rates of 4.6% (23 of 501 cases) in the ODD arms and 6.9% (34 of 494 cases) in the MDD arms. The fixed-effects risk ratio was 0.71 (95% confidence interval [CI]: 0.45-1.11). A statistically significant benefit was seen with ODD over MDD in trials using amikacin, whereas no statistical significance was seen in trials using other antibiotics. The pooled clinical failure rates were 6.7% (22 of 330 cases) in the ODD arms and 10.4% (34 of 327 cases) in the MDD arms. The fixed-effects risk ratio was 0.67 (95% CI: 0.42-1.07). The pooled microbiologic failure rates were 1.8% (5 of 283 cases) with ODD and 4.0% (11 of 275 cases) with MDD. The fixed-effects risk ratio was 0.51 (95% CI: 0.22-1.18). NEPHROTOXICITY: There was no significant difference between ODD and MDD in the primary nephrotoxicity outcomes. Secondary nephrotoxicity outcomes were significantly better with ODD. The pooled primary nephrotoxicity rates were 1.6% (15 of 955 cases) in the ODD arms and 1.6% (15 of 923 cases) in the MDD arms. The fixed-effects risk ratio was 0.97 (95% CI: 0.55-1.69). The pooled secondary nephrotoxicity rates were 4.4% (3 of 69 cases) in the ODD arms and 15.9% (11 of 69 cases) in the MDD arms, suggesting a statistically significant superiority of ODD. The fixed-effects risk ratio was 0.33 (95% CI: 0.12-0.89). Results were consistent across types of clinical settings and aminoglycosides. OTOTOXICITY: There was no significant difference between ODD and MDD in the primary ototoxicity outcomes. The pooled ototoxicity rates for studies that provided auditory testing results were 2.3% (10 of 436 cases) in the ODD arms and 2.0% (8 of 406 cases) in the MDD arms. The fixed-effects risk ratio was 1.06 (95% CI: 0.51-2.19). In studies that provided clinical vestibular function testing results, no toxicity was documented among 209 patients given ODD and 206 patients given MDD. Studies noting only the clinical impression of hearing impairment also failed to identify any toxicity (ODD: 114 cases; MDD: 114 cases). SUBGROUP AND BIAS ANALYSES: We detected no statistically significant differences between ODD and MDD in any of the examined subgroups (neonatal intensive care unit, cystic fibrosis, cancer, or urinary tract infection), with respect to combined clinical or microbiologic failure outcomes, primary nephrotoxicity outcomes, or ototoxicity (based on auditory testing), when sufficient data were available. Moreover, there was no significant relationship between the effect size (risk ratio) and the trial size for any of the outcomes. DATA INTERPRETATION: Clinical failures were uncommon in the pediatric trials, regardless of the regimen used. If anything, fewer clinical failures tended to occur with ODD. Moreover, we observed a trend toward decreased bacteriologic failures. One meta-analysis of adult data suggested that ODD might reduce nephrotoxicity, whereas other meta-analyses showed nonsignificant trends or no difference in nephrotoxicity outcomes. In our meta-analysis, we were not able to show any reduction in the risk of primary nephrotoxicity outcomes with ODD. However, the event rate was much lower among children, compared with adults, and the secondary nephrotoxicity outcomes favored ODD. Finally, although the 2 regimens seemed equivalent with respect to ototoxicity, reporting on ototoxicity outcomes was incomplete. Reassuringly, even in the trials that performed auditory testing, the rates of ototoxicity in the MDD arms were very low. These results were consistent with meta-analyses of adult data, which showed no difference in ototoxicity rates between ODD and MDD.

CONCLUSIONS

Although single trials have been small, the available randomized evidence supports the general adoption of ODD of aminoglycosides in pediatric clinical practice. This approach minimizes cost, simplifies administration, and provides similar or even potentially improved efficacy and safety, compared with MDD of these drugs.

A randomised, controlled trial of once daily and multi-dose daily gentamicin in young Kenyan infants

AIMS

To test the suitability of a simple once daily (OD) gentamicin regimen for use in young infants where routine therapeutic drug monitoring is not possible.

METHODS

In an open, randomised, controlled trial, infants with suspected severe sepsis admitted to a Kenyan, rural district hospital received a novel, OD gentamicin regimen or routine multi-dose (MD) regimens.

RESULTS

A total of 297 infants (over 40% < or =7 days) were randomised per protocol; 292 contributed at least some data for analysis of pharmacological endpoints. One hour after the first dose, 5% (7/136) and 28% (35/123) of infants in OD and MD arms respectively had plasma gentamicin concentrations <4 microg/ml (a surrogate of treatment inadequacy). Geometric mean gentamicin concentrations at this time were 9.0 microg/ml (95% CI 8.3 to 9.9) and 4.7 microg/ml (95% CI 4.2 to 5.3) respectively. By the fourth day, pre-dose concentrations > or =2 microg/ml (a surrogate of potential treatment toxicity) were found in 6% (5/89) and 24% (21/86) of infants respectively. Mortality was similar in both groups and clinically insignificant, although potential gentamicin induced renal toxicity was observed in <2% infants.

CONCLUSIONS

A "two, four, six, eight" OD gentamicin regime, appropriate for premature infants and those in the first days and weeks of life, seems a suitable, safe prescribing guide in resource poor settings.

Once-daily gentamicin dosing for the preterm and term newborn: proposal for a simple regimen that achieves target levels

OBJECTIVE

Based on recent safety and efficacy data, combined with the known pharmacokinetic parameters of aminoglycosides in the newborn, once-daily gentamicin should be preferable to the many other dosing regimens currently in use. Although there are growing data to support its use in term newborns, experience with preterm infants is more limited. In our Neonatal Intensive Care Unit, we experienced difficulties regarding complicated dosing regimens, actual dosing errors, and the tendency to check trough and peak levels around the third dose for infants receiving only a 48 hour course. Therefore, we conducted a quality improvement initiative in which we developed and tested a clinical practice guideline for the use of once-daily gentamicin for preterm and term infants that we hoped would yield trough and peak levels in our target range.

METHODS

We combined a review of the published English language literature with pharmacokinetic analysis of our own data prior to initiation of this new regimen to design the following dosing regimen: <35 weeks gestation: 3 mg/kg q 24 hours, > or =35 weeks gestation: 4 mg/kg q 24 hours. Our goal serum levels were a trough < or =2 microg/ml and a peak between 6 and 12 microg/ml. We collected and analyzed trough and peak levels from all infants receiving this dosing regimen in the first week of life for at least 72 hours between 3/1/99 and 12/31/00.

RESULTS

In total, 214 babies met our inclusion criteria, 75 of whom were <35 weeks gestation. 100% of babies of all gestational ages had a nontoxic trough level. For infants <35 weeks gestation, 79% had a therapeutic peak level, with a mean value of 6.8 microg/ml. For infants of at least 35 weeks gestation, 93% had a therapeutic peak level, with a mean value of 8.4 microg/ml. 92% of nontherapeutic peaks were too low.

CONCLUSION

This study of once-daily gentamicin represents the largest sample size of pre-term infants published to date. The proposed regimen is simple and yields a high proportion of desirable levels. We recommend it for use in preterm and term newborns.

Pharmacodynamics and dosing of aminoglycosides

Aminoglycosides are concentration-dependent killing agents whose pharmacodynamic predictors of efficacy are the area-under-the-curve to minimum inhibitory concentration ratio and the peak to minimum inhibitory concentration ratio. Prospective studies have shown that these agents can be given once-daily or less frequently in most clinical settings, with equal efficacy and possible reduced toxicity. Dosages for different clinical settings have been studied and methods are available to monitor once-daily dosing.

Population pharmacokinetics of intramuscular gentamicin administered to young infants with suspected severe sepsis in Kenya

AIMS

To determine the population pharmacokinetics of intramuscular (i.m.) gentamicin in African infants with suspected severe sepsis.

METHODS

Samples were withdrawn 1 h after a single i.m. injection of 8 mg x kg(-1) gentamicin and the next morning prior to any further dosing. Concentration-time data were analysed with the population pharmacokinetic package NONMEM. Data were fitted using a one-compartment model with a log-normal model for interindividual variability and an additive residual error model. The influence of a range of clinical characteristics was tested on the pharmacokinetics of intramuscular gentamicin and the effect of incorporating interindividual variability on bioavailability was examined.

RESULTS

The data set comprised 107 patients and 203 concentrations. Peak concentrations ranged from 3.0 mg x L(-1) to 19.8 mg x L(-1) (median 10.6 mg x L(-1)) and 'next day' samples from 0.3 mg x L(-1) to 6.2 mg x L(-1). The best models were clearance/bioavailability (CL) (L x h(-1)) = 0.0913 x weight (kg) x (age (days) + 1)/11)0.130 and volume of distribution/bioavailability (V) = 2.02 x (1 + 0.277 x (weight -3)). Therefore, an infant with the median weight of 3 kg and age 10 days would have a predicted CL of 0.274 L x h(-1) and V of 2.02 L. Interindividual variability in CL was 40% and in V was 42%. This model required a term for covariance between CL and V. When variability in bioavailability was introduced as an alternative model, interindividual variability in CL was 22%, in V 18% and in relative bioavailability 36%.

CONCLUSIONS

Intramuscular administration of 8 mg x kg(-1) gentamicin daily to infants gives mean 1 h peak concentration of 10.6 mg x L(-1) and a trough concentration of less than 2 mg x L(-1). Wide variability in the peak concentration may reflect variable absorption rate or bioavailability.

A gentamicin pharmacokinetic population model and once-daily dosing algorithm for neonates

STUDY OBJECTIVE

To develop a gentamicin pharmacokinetic population model and once-daily dosing algorithm for neonates younger than 10 days.

DESIGN

Prospective, open-label study.

SETTING

Neonatal intensive care unit.

PATIENTS

One hundred thirty-nine neonates prescribed gentamicin.

MEASUREMENTS AND MAIN RESULTS

Gentamicin peak and trough serum concentrations were collected from 139 neonates divided into three groups who were receiving one of the following intravenous 24-hour gentamicin regimens during the first 10 days of life, based on gestational age and birth weight (group 1, < 28 wks, 2.5 mg/kg; group 2, 28-34 wks, 3 mg/kg; and group 3, > 34 wks, 4 mg/kg). A structural model was developed in ADAPT II software using a MAP Bayesian approach. Final population parameter estimates were calculated using iterative two-stage analysis. The median (range) gestational age and birth weight, respectively, were 32 weeks (23-42 wks) and 1.92 kg (0.47-5.00 kg). The final one-compartmental linear model had a median (range) gentamicin total clearance, half-life, and volume of distribution of 0.0709 L/hour (0.0151-0.246 L/hr), 8.59 hours (4.88-16.9 hrs), and 0.262 L (0.0903-0.929 L), respectively. Total clearance increased as gestational age increased (p<0.001). Group 1 (10.2 hrs) had a significantly longer half-life than either group 2 (8.89 hrs, p<0.01) or group 3 (6.98 hrs, p<0.01). Total clearance was associated with gestational age and birth weight: clearance (L/hr) = (0.00504 + [0.00108 x gestational age]) x birth weight (coefficient of determination [r2] = 0.897), and volume of distribution was associated with birth weight (r2 = 0.700). The following dosing algorithm was designed to reach a therapeutic 24-hour area under the curve (87.5 mg/L x hr) in neonates during the first 10 days after birth: 24-hour gentamicin dose (mg) = (0.441 + [0.0945 x gestational age]) x birth weight.

CONCLUSION

This dosing algorithm provides a new approach for determining initial gentamicin dosing regimens in neonates; however, clinical validation is required.

[Once-daily gentamicin dosing versus thrice-daily dosing in infants with acute pyelonephritis]

BACKGROUND

Once-daily dosing (ODD) of gentamicin is advocated as an effective and safe treatment of Gram-negative bacterial infections in adults. There are insufficient data in the literature to justify its use in infants.

OBJECTIVES

To compare the efficacy of ODD of gentamicin with that of classical thrice-daily (t.i.d.) administration in infants with acute pyelonephritis.

METHODS

We performed a quasi-experimental study comparing 33 infants who received ODD of gentamicin with a historical control group of 25 infants treated with gentamicin t.i.d. Leukocytosis, C-reactive protein, creatinine, gentamicin dose, peak and trough values, time required for disappearance of fever, and outcome were analyzed.

RESULTS

The mean doses of gentamicin (mg/kg/day) were higher in the t.i.d. group (6.4 1.14) than in the ODD group (5.06 0.22; p < 0.001). Peak serum gentamicin concentrations (micro g/ml) were significantly higher in the ODD group (9.32 1.4) than in the t.i.d. group (5.09 1.15; p < 0.001). Mean trough gentamicin concentrations (micro g/ml) were lower in the ODD group than in the t.i.d. group (0.23 0.26 vs 0.78 0.45; p 0.001). There were no significant differences in the duration of fever between the groups (30.64 32 hours in the t.i.d. group vs. 28.57 32 hours in the ODD group). Serum creatinine levels were normal during treatment in both groups. In all patients outcome was good and no adverse effects were noted.

CONCLUSIONS

Treatment with ODD of gentamicin in our population of infants with acute pyelonephritis was as effective as traditional administration t.i.d. and possibly was equally safe or safer.

Efficacy and tolerability of extended-interval aminoglycoside administration in pediatric patients

Aminoglycosides are commonly used to treat serious Gram-negative infections in pediatric patients. An effort to improve the efficacy and tolerability of this antibiotic class has led to evaluation of extended-interval aminoglycoside administration (EIAA). EIAA is designed to achieve higher peak plasma aminoglycoside concentrations, with relatively undetectable trough concentrations, when compared with conventional aminoglycoside administration (CAA), and is therefore expected to be markedly effective and to reduce drug accumulation and prevent nephrotoxicity and ototoxicity. Clinical trials evaluating EIAA in neonates included patients with suspected Gram-negative infections requiring short courses of aminoglycoside therapy. Consequently, comparative efficacy of EIAA versus CAA could not be assessed. In addition, ototoxicity was often not assessed, and nephrotoxicity was virtually undetectable. Similarly, trials evaluating EIAA versus CAA in infants and children have not demonstrated a difference in outcomes. The use of EIAA in children with febrile neutropenia has been evaluated primarily with amikacin. The incidences of nephrotoxicity and ototoxicity were low, and were similar between EIAA and CAA. No deaths were reported in any of these studies; however, this could be related to the inclusion of patients with undocumented bacteremia. Further investigation of EIAA is necessary in patients with documented bacteremia, since plasma aminoglycoside concentrations were undetectable for most of the dosage interval in children with febrile neutropenia who were treated once daily. Overall, clinical studies suggest that EIAA has similar efficacy to, and no higher risk of toxicity than, CAA in neonates, infants, and children. A few evaluations have also demonstrated that EIAA is cost-effective in neonates and in children with febrile neutropenia. Future studies evaluating the efficacy and tolerability of EIAA in pediatric patients with documented systemic infections should be prospective, randomized, controlled trials with sample sizes sufficient to detect differences between administration methods. Further evaluations should also address the optimal dosage and cost-effectiveness of EIAA in infants and children.

Comparison of once-daily versus twice-daily gentamicin dosing regimens in infants > or = 2500 g

OBJECTIVE

There is no uniformity in the current recommendations of dosing regimen of gentamicin for neonates. We conducted a prospective, randomized, controlled trial to compare a once-daily dosing regimen to the twice-daily dosing regimen for neonates > or = 2500 g during the first 7 days after birth.

STUDY DESIGN

Infants > or = 2500 g admitted to the Neonatal Intensive Care Unit and prescribed gentamicin for suspected bacterial infection were randomized to receive either 4 mg/kg every 24 hours, study group (n=20), or a standard regimen of 2.5 mg/kg every 12 hours, control group (n=21). Serum gentamicin concentrations (SGCs) were followed and gentamicin pharmacokinetics calculated on all infants.

RESULTS

Peak SGC 30 minutes after the first dose was 8.2+/-1.7 microg/ml in the study group, compared to 6.4+/-1.5 microg/ml in the control group (p=0.001). Ninety-five percent of study group infants, compared to 81% of the control group, had peak SGCs in therapeutic range after the first dose. Peak SGC at 48 hours (steady state) was 8.9+/-1.5 in the study group and 6.8+/-1.1 in the control group (p=0.0001). On further analysis, a significantly higher percentage of infants in the study group, compared to the control group, had peak SGCs in higher therapeutic ranges of 6 to 12 microg/ml as well as 8 to 12 microg/ml. None of the study infants, compared to six control infants, had trough SGCs > or = 2 microg/ml at steady state. Thus, none of the study group infants, versus six of the control group infants, needed a dosing adjustment at 48 hours (p=0.02, Fisher's exact test).

CONCLUSION

We found that 4 mg/kg gentamicin given every 24 hours achieved significantly higher peak SGCs and safe trough concentrations in all infants, compared to the twice-daily regimen of 2.5 mg/kg. We suggest that SGCs may not need to be followed in term infants prescribed a short course of this once-daily regimen for suspected early-onset sepsis if renal functions are normal.

Nonparametric population pharmacokinetic analysis of amikacin in neonates, infants, and children

The therapeutic and toxic effects of amikacin are known to depend on its concentration in plasma, but the pharmacokinetics of this drug in neonates, infants, and children and the influences of clinical and biological variables have been only partially assessed. Therapeutic drug monitoring data collected from 155 patients (49 neonates, 77 infants, and 29 children) receiving amikacin were analyzed by a nonparametric population-based approach, the nonparametric maximum-likelihood method. We assessed the effects of gestational and postnatal age, weight, Apgar score, and plasma creatinine and urea concentrations on pharmacokinetic parameters. There is no specific formulation of amikacin for neonates and infants. We therefore used an error model to account for errors due to dilution during preparation of the infusion. The covariates that reduced the variance of clearance from plasma and the volume of distribution by more than 10% were postnatal age (43 and 28%, respectively) and body weight (30.4 and 17.4%, respectively). The expected reduction of clearance was about 10% for the plasma creatinine concentration. The other covariates studied (Apgar scores, plasma urea concentration, gestational age, sex) were found to have little effect. Simulations showed that a smaller percentage of patients had a maximum concentration in plasma/MIC ratio greater than 8 with a regimen of 7.5 mg/kg of body weight twice daily than with a regimen of 15 mg/kg once a day for MICs of 1 to 8 mg/liter.

Comparison of two gentamicin dosing schedules in very low birth weight infants

BACKGROUND

Several dosing schedules for gentamicin have been recommended for very low birth weight infants during the early neonatal period. We conducted a prospective, randomized, controlled trial to compare efficacy and pharmacokinetics of two dosing schedules in preterm neonates.

METHODS

Fifty-eight very low birth weight infants (600 to 1500 g), prescribed gentamicin for treatment of suspected sepsis during the first week after birth, were randomized to receive either the new dosing schedule [every 48 h (q48h)] or the existing dosing schedule [every 24 h (q24h)]. Infants in the "q48h" group received gentamicin at 5.0 or 4.5 mg/kg/dose q48h depending on weight group and infants in the "q24h" group received 2.5 or 3.0 mg/kg/dose q24h. Peak and trough serum gentamicin concentrations were monitored.

RESULTS

Peak serum gentamicin concentrations after the first dose were significantly higher in the q48h infants than in q24h infants (8.19 +/- 1.3 vs. 6.04 +/- 2.2, P = 0.00001). Ninety percent of all peak serum gentamicin concentrations in the q48h group were in a higher therapeutic range of 6 to 12 microg/ml as compared with 55% of q24h (P = 0.0005). None of the q48h infants had subtherapeutic serum gentamicin concentrations immediately after administration of the first dose as compared with 36% of q24h infants (P < 0.005). Eighteen percent of q24h infants continued to have peak serum gentamicin concentrations in subtherapeutic range even after the third dose at 48 h. Trough serum gentamicin concentrations were significantly lower in q48h infants than in q24h infants. However, 9 of 30 (30%) q48h infants had trough serum gentamicin concentrations of < or = 0.5 microg/ml before the dose at 48 h and 4 of the 9 had serum gentamicin concentrations of <1 microg/ml at 24 h after the first dose.

CONCLUSIONS

The q48h dosing schedule of gentamicin given to very low birth weight infants during the first week after birth achieved therapeutic serum gentamicin concentrations and potentially higher peak to MIC ratios for microorganisms in all infants. However, nearly one-third of the infants had extremely low serum gentamicin concentrations before the next dose. A dosing interval of 36 h might be optimal for bactericidal activity and avoid bacterial growth during prolonged periods of extremely low serum gentamicin concentrations; this dosing interval warrants study.

Once daily dosing of gentamicin in infants and children

BACKGROUND

Aminoglycosides are frequently used in children. The standard daily dosing (SDD) in infants and children is twice or three times daily depending on age. The aim of this paper is to review the current data regarding the safety and effectiveness of once daily dosing (ODD) of gentamicin in children.

METHODS

A Medline search was conducted for comparison studies between ODD and SDD of gentamicin in children in term of pharmacokinetic indices and toxicity.

RESULTS

Overall 13 studies describing ODD of gentamicin in children were found suitable for this review. In most studies steady state peak serum gentamicin concentrations were significantly higher in the ODD groups. Steady state trough concentrations >2 microg/ml were documented in 5 to 55% of patients treated with the SDD as compared with 0 to 24% in the ODD groups. The mode of dosing did not affect the volume of distribution; however, the t1/2 was significantly longer in the ODD groups. ODD was found to be cost-saving. In a few studies the efficacy of ODD was similar to that of SDD.

CONCLUSIONS

These studies suggest that ODD compared with SDD of gentamicin is theoretically more efficacious and has no higher toxicity at 48 to 96 h in neonates and at 3 to 10 days of therapy in older infants and children.

A multicenter evaluation of gentamicin therapy in the neonatal intensive care unit

STUDY OBJECTIVE

To evaluate traditional nomogram (TN) versus individualized pharmacokinetic gentamicin dosing practices in neonatal intensive care units, focusing on achieving target therapeutic concentrations (peak > 8 microg/ml, trough < 2 microg/ml), number of dosing changes, number of concentrations obtained, and evidence of nephrotoxicity.

DESIGN

Retrospective chart review.

SETTING

Three neonatal intensive care units.

PATIENTS

Three hundred nine infants prescribed gentamicin.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

Sixty-seven percent of patients receiving pharmacokinetic dosing had initial peak concentrations of 8 microg/ml or greater compared with 7% of patients receiving TN dosing (p<0.001). Trough concentrations exceeding 2 microg/ml were reported in 23% of patients receiving TN dosing compared with 2% of pharmacokinetic-dosed patients (p<0.001). Forty-two percent and 6%, respectively, required dosage adjustments (p<0.01). The mean number of concentrations obtained per patient was 2.8 and 2.1, respectively (p<0.01). Neither group had evidence of gentamicin-related nephrotoxicity.

CONCLUSION

Compared with TN dosing, administering gentamicin loading doses and performing initial pharmacokinetic analysis resulted in rapid attainment of desired concentrations and fewer dosage adjustments, and allowed for a decrease in the number of gentamicin concentrations.