A randomized comparison of the safety and efficacy of once-daily gentamicin or thrice-daily gentamicin in combination with ticarcillin-clavulanate

Beta lactam antibiotic monotherapy versus beta lactam-aminoglycoside antibiotic combination therapy for sepsis

BACKGROUND

Optimal antibiotic treatment for sepsis is imperative. Combining a beta lactam antibiotic with an aminoglycoside antibiotic may provide certain advantages over beta lactam monotherapy.

OBJECTIVES

Our objectives were to compare beta lactam monotherapy versus beta lactam-aminoglycoside combination therapy in patients with sepsis and to estimate the rate of adverse effects with each treatment regimen, including the development of bacterial resistance to antibiotics.

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 11); MEDLINE (1966 to 4 November 2013); EMBASE (1980 to November 2013); LILACS (1982 to November 2013); and conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (1995 to 2013). We scanned citations of all identified studies and contacted all corresponding authors. In our previous review, we searched the databases to July 2004.

SELECTION CRITERIA

We included randomized and quasi-randomized trials comparing any beta lactam monotherapy versus any combination of a beta lactam with an aminoglycoside for sepsis.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause mortality. Secondary outcomes included treatment failure, superinfections and adverse events. Two review authors independently collected data. We pooled risk ratios (RRs) with 95% confidence intervals (CIs) using the fixed-effect model. We extracted outcomes by intention-to-treat analysis whenever possible.

MAIN RESULTS

We included 69 trials that randomly assigned 7863 participants. Twenty-two trials compared the same beta lactam in both study arms, while the remaining trials compared different beta lactams using a broader-spectrum beta lactam in the monotherapy arm. In trials comparing the same beta lactam, we observed no difference between study groups with regard to all-cause mortality (RR 0.97, 95% CI 0.73 to 1.30) and clinical failure (RR 1.11, 95% CI 0.95 to 1.29). In studies comparing different beta lactams, we observed a trend for benefit with monotherapy for all-cause mortality (RR 0.85, 95% CI 0.71 to 1.01) and a significant advantage for clinical failure (RR 0.75, 95% CI 0.67 to 0.84). No significant disparities emerged from subgroup and sensitivity analyses, including assessment of participants with Gram-negative infection. The subgroup of Pseudomonas aeruginosa infections was underpowered to examine effects. Results for mortality were classified as low quality of evidence mainly as the result of imprecision. Results for failure were classified as very low quality of evidence because of indirectness of the outcome and possible detection bias in non-blinded trials. We detected no differences in the rate of development of resistance. Nephrotoxicity was significantly less frequent with monotherapy (RR 0.30, 95% CI 0.23 to 0.39). We found no heterogeneity for all these comparisons.We included a small subset of studies addressing participants with Gram-positive infection, mainly endocarditis. We identified no difference between monotherapy and combination therapy in these studies.

AUTHORS' CONCLUSIONS

The addition of an aminoglycoside to beta lactams for sepsis should be discouraged. All-cause mortality rates are unchanged. Combination treatment carries a significant risk of nephrotoxicity.

Evaluation of extended interval dosing aminoglycosides in the morbidly obese population

Aminoglycoside dosing has been studied in the obese population, typically recommending an adjusted weight utilizing a 40% dosing weight correction factor (IBW + 0.4 × (TBW-IBW)). These studies included limited numbers of morbidly obese patients and were not done in the era of extended interval aminoglycoside dosing. Here, we report a retrospective evaluation of morbidly obese patients receiving gentamicin or tobramycin at our hospital. The objective of this study was to evaluate the accuracy of the commonly recommended adjusted weight for weight-based dosing. There were 31 morbidly obese patients who received gentamicin or tobramycin 5-7 mg/kg every 24 hours using a 40% dosing weight correction factor. Our institution utilizes 16-hour postdose concentrations to monitor extended interval aminoglycosides. Twenty-two of the 31 patients (71%) achieved an appropriate serum drug concentration. Four patients (13%) were found to be supratherapeutic and 5 patients (16%) subtherapeutic. The only variable that correlated with supratherapeutic levels was older age (P = 0.0378). Our study helps to validate the current dosing weight correction factor (40%) in the morbidly obese population. We recommend caution when dosing aminoglycosides in morbidly obese patients who are of older age.

Antibiotic pharmacokinetic and pharmacodynamic considerations in patients with kidney disease

Although pharmacokinetic changes occurring in kidney disease are well described, pharmacodynamics in kidney disease is rarely considered. Knowledge of pharmacodynamic principles can allow a clinician to maximize an antibiotic's effectiveness while minimizing adverse effects and antibacterial resistance. An antibiotic's pharmacokinetic and pharmacodynamic profiles should drive dose adjustment decisions in patients with kidney disease. For example, although the half-lives of beta-lactams and aminoglycosides are both prolonged in these patients, beta-lactams exhibit time-dependent antibacterial activity; consequently, maintenance doses should be smaller but given at the same interval. In contrast, aminoglycosides are concentration-dependent antibiotics; hence prolongation of the dosing interval while using larger doses may be advantageous. The timing of drug administration in relation to hemodialysis may be used to achieve specific pharmacodynamic goals. Aminoglycosides given before hemodialysis generate high peaks, whereas subsequent dialytic drug removal minimizes the area under the serum concentration-time curve, potentially decreasing the risk of developing toxicity. Furthermore, new dialysis prescribing patterns (eg, automated peritoneal dialysis, nocturnal dialysis) affect pharmacokinetic and pharmacodynamic parameters in ways not appreciated by clinicians. Studies quantifying the often considerable drug removal with these therapies, as well as efforts to identify pharmacodynamic targets in patients with kidney disease are essential. This paper reviews pharmacodynamic as well as pharmacokinetic issues that should be considered when prescribing antibiotics to treat infections in this population.

Aerosolized tobramycin in the treatment of ventilator-associated pneumonia: a pilot study

OBJECTIVE

To evaluate the efficacy and safety of inhaled tobramycin (TOBI) in the treatment of ventilator-associated pneumonia (VAP) in a randomized, double-blind pilot study.

PATIENTS AND METHODS

Ten patients from a cohort of 108 mechanically ventilated patients with documented clinical and bacteriological evidence of VAP caused by Pseudomonas aeruginosa or Acinetobacter spp. in the surgical and trauma intensive care units of a university teaching hospital were randomized to receive either TOBI (n = 5) or intravenous tobramycin (TOBRA; n = 5). The two groups were similar in their Acute Physiology and Chronic Health Evaluation (APACHE) score, Clinical Pulmonary Infection Score (CPIS), and Multiple Organ Dysfunction Score (MODS) prior to randomization. The primary outcome measure was resolution of pneumonia. The CPIS and MODS were used as objective indicators of clinical progress.

RESULTS

All TOBI patients had clinical resolution of VAP. Two TOBRA patients were considered failures. One had deterioration in MODS, and the other had doubling of his serum creatinine concentration. The patients treated with TOBI may have had more ventilator-free days than those receiving TOBRA, but the difference was not statistically significant owing to the small sample size (24 +/- 3 vs. 14 +/- 13 days; p = 0.12).

CONCLUSION

Aerosolized tobramycin for the treatment of VAP appeared safe and effective in this pilot study. A larger study is warranted to determine if aerosolized tobramycin will lead to better outcomes than intravenous tobramycin when used for the treatment of VAP.

Pharmacodynamics of antimicrobials: treatment optimisation

As bacterial resistance continues to increase, optimising the potential for successful clinical outcomes with antimicrobial therapy requires consideration of pharmacodynamic concepts in order to maximise bacterial eradication and minimise the potential for further resistance. Based on the pharmacodynamic characteristics of specific antibiotics, dosage modifications can be implemented to improve the likelihood of bactericidal exposure. Considering their concentration-dependent bactericidal activity, aminoglycosides benefit from increased dosages and infrequent administration, so as to achieve a maximum concentration/minimum inhibitory concentration (MIC) of 10-12. In contrast, beta-lactams are concentration-independent killers and benefit greatest by increasing the time above the MIC (T > MIC). This can be accomplished with the use of prolonged or continuous infusion. By optimising pharmacodynamic parameters with these methodologies, successful treatment of pathogens may be possible in patient populations for whom standard dosing regimens are not effective.

Beta lactam antibiotic monotherapy versus beta lactam-aminoglycoside antibiotic combination therapy for sepsis

BACKGROUND

Optimal antibiotic treatment for sepsis is imperative. Combining a beta-lactam antibiotic with an aminoglycoside antibiotic may have certain advantages over beta-lactam monotherapy.

OBJECTIVES

We compared clinical outcomes for beta lactam-aminoglycoside combination therapy versus beta lactam monotherapy for sepsis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library, Issue 3, 2004); MEDLINE (1966 to July 2004); EMBASE (1980 to March 2003); LILACS (1982 to July 2004); and conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (1995 to 2003). We scanned citations of all identified studies and contacted all corresponding authors.

SELECTION CRITERIA

We included randomized and quasi-randomized trials comparing any beta-lactam monotherapy to any combination of one beta-lactam and one aminoglycoside for sepsis.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause fatality. Secondary outcomes included treatment failure, superinfections, colonization, and adverse events. Two authors independently collected data. We pooled relative risks (RR) with their 95% confidence intervals (CI) using the fixed effect model. We extracted outcomes by intention-to-treat analysis whenever possible.

MAIN RESULTS

We included 64 trials, randomizing 7586 patients. Twenty trials compared the same beta-lactam in both study arms, while the remaining compared different beta-lactams using a broader spectrum beta-lactam in the monotherapy arm. In studies comparing the same beta-lactam, we observed no difference between study groups with regard to all-cause fatality, RR 1.01 (95% CI 0.75-1.35) and clinical failure, RR 1.11 (95% CI 0.95-1.29). In studies comparing different beta-lactams, we observed an advantage to monotherapy: all cause fatality RR 0.85 (95% CI 0.71-1.01), clinical failure RR 0.77 (95% CI 0.69-0.86). No significant disparities emerged from subgroup and sensitivity analyses, including the assessment of patients with Gram-negative and Pseudomonas aeruginosa infections. We detected no differences in the rate of resistance development. Adverse events rates did not differ significantly between the study groups overall, although nephrotoxicity was significantly more frequent with combination therapy, RR 0.30 (95% CI 0.23-0.39). We found no heterogeneity for all comparisons. We included a small subset of studies addressing patients with Gram-positive infections, mainly endocarditis. We identified no difference between monotherapy and combination therapy in these studies.

AUTHORS' CONCLUSIONS

The addition of an aminoglycoside to beta-lactams for sepsis should be discouraged. All-cause fatality rates are unchanged. Combination treatment carries a significant risk of nephrotoxicity.

Effect of Aminoglycoside and β‐Lactam Combination Therapy versus β‐Lactam Monotherapy on the Emergence of Antimicrobial Resistance: A Meta‐analysis of Randomized, Controlled Trials

BACKGROUND

The addition of an aminoglycoside to a beta -lactam therapy regimen has been suggested to have a beneficial effect in delaying or preventing the development of antimicrobial resistance. We studied the effect of aminoglycoside/ beta -lactam combination therapy versus beta-lactam monotherapy on the emergence of resistance.

METHODS

We performed a meta-analysis of randomized, controlled trials (RCTs) that compared aminoglycoside/ beta-lactam combination therapy with beta-lactam monotherapy and that reported data regarding the emergence of resistance (primary outcome) and/or development of superinfection, treatment failure, treatment failure attributable to emergence of resistance, treatment failure attributable to superinfection, all-cause mortality during treatment, and mortality due to infection. Data for this meta-analysis were identified from the PubMed database, Current Contents database, Cochrane central register of controlled trials, and references in relevant articles.

RESULTS

A total of 8 RCTs were included in the analysis. Beta -lactam monotherapy was not associated with a greater emergence of resistance than was the aminoglycoside/ beta-lactam combination (odds ratio [OR], 0.90; 95% confidence interval [CI], 0.56-1.47). Actually, beta -lactam monotherapy was associated with fewer superinfections (OR, 0.62; 95% CI, 0.42-0.93) and fewer treatment failures (OR, 0.62; 95% CI, 0.38-1.01). Rates of treatment failure attributable to emergence of resistance (OR, 3.09; 95% CI, 0.75-12.82), treatment failure attributable to superinfection (OR, 0.60; 95% CI, 0.33-1.10), all-cause mortality during treatment (OR, 0.70; 95% CI, 0.40-1.25), and mortality due to infection (OR, 0.74; 95% CI, 0.46-1.21) did not differ significantly between the 2 regimens.

CONCLUSIONS

Compared with beta-lactam monotherapy, the aminoglycoside/ beta-lactam combination was not associated with a beneficial effect on the development of antimicrobial resistance among initially antimicrobial-susceptible isolates.

Application of Bayes theorem to aminoglycoside-associated nephrotoxicity: comparison of extended-interval dosing, individualized pharmacokinetic monitoring, and multiple-daily dosing

The objective of this study was to examine the incidence of aminoglycoside-associated nephrotoxicity related to extended-interval dosing, individualized pharmacokinetic monitoring, and multiple-daily dosing by applying Bayes theorem. An electronic literature search of MEDLINE (1966-2003) and a manual search of references from published meta-analyses and review articles were performed. Studies using extended-interval dosing, individualized pharmacokinetic monitoring, or multiple-daily dosing and reported aminoglycoside-associated nephrotoxicity for patients > or = 16 years of age were included. Quality scores were assigned based on the rigor of definition of aminoglycoside-associated nephrotoxicity, duration of therapy, and length of follow-up of renal function after completion of therapy. Inclusion criteria were then based on these quality scores. Quantitative data on the incidence of aminoglycoside-associated nephrotoxicity were abstracted. Twelve extended-interval dosing studies (n = 916), 10 individualized pharmacokinetic monitoring studies (n = 2066), and 27 multiple-daily dosing studies (n = 4251) met the inclusion criteria. Prior probabilities of aminoglycoside-associated nephrotoxicity were derived from a combination of a review of published studies and expert judgment. The maximum densities for the final posterior probabilities of aminoglycoside-associated nephrotoxicity for extended-interval dosing, individualized pharmacokinetic monitoring, and multiple-daily dosing were located at 12% to 13%, 10% to 11%, and 13% to 14%, respectively. Application of Bayes theorem demonstrates that aminoglycoside dosing by individualized pharmacokinetic monitoring results in less aminoglycoside-associated nephrotoxicity than extended-interval dosing or multiple-daily dosing.

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.

The effect of vecuronium is enhanced by a large rather than a modest dose of gentamicin as compared with no preoperative gentamicin

We compared the effect of two doses of gentamicin versus no gentamicin (NG) given before surgery on the neuromuscular relaxant effect of vecuronium. Seventy patients (intraabdominal procedures) were randomly allocated to receive preoperative large-dose (4 mg/kg) gentamicin (LD), a modest dose (1.2 mg/kg) of gentamicin (MD), or NG. No more than one dose of gentamicin was given before the vecuronium administration. Serum gentamicin levels, the time for 25% recovery of the first twitch in the train-of-four after a bolus of vecuronium, and the time from cessation of the vecuronium infusion to extubation of the trachea were estimated. Serum gentamicin levels were higher (P < 0.001) for LD than MD. The time for 25% recovery of the first twitch after the vecuronium bolus was slightly longer with LD than MD (P = 0.06) and longer in LD than NG (P = 0.001) (42.9 +/- 23.6 min versus 36.2 +/- 17 min and 27.4 +/- 9 min, respectively). The time to extubation was similar with LD and MD and longer for LD than NG (P = 0.008) (34.7 +/- 19.2 min versus 27.4 +/- 19.3 min and 19.4 +/- 10.1 min, respectively). The differences in these times were insignificant between MD and NG. Gentamicin administered as a LD rather than MD enhanced the neuromuscular blockade of vecuronium as compared with NG given before surgery.

IMPLICATIONS

We demonstrated that the neuromuscular relaxant effect of vecuronium is enhanced by a large (4 mg/kg) rather than a modest (1.2 mg/kg) dose of gentamicin as compared with no gentamicin given before surgery.

Evaluation of four once-daily aminoglycoside dosing nomograms

STUDY OBJECTIVE

To evaluate the accuracy of four once-daily aminoglycoside dosing nomograms in producing the desired gentamicin peak concentration (Cmax) target of 20 microg/ml in patients with varying degrees of renal function.

DESIGN

Retrospective analysis using prospectively collected pharmacokinetic data.

SETTING

Rural teaching hospital.

PATIENTS

Ninety patients receiving intravenous gentamicin divided into three groups (30 patients each) determined by estimated renal function: group 1, creatinine clearance (Cl(cr),) 60 ml/minute or greater; group 2, Cl(cr) 40-59 ml/minute; group 3, Cl(cr) 20-39 ml/minute. Intervention. Serum gentamicin concentrations were collected for a 2-point (two consecutive infusions and one predose and one postdose concentration sampled during steady state) or 3-point (single infusion and one predose and two postdose concentrations at least 1.5 estimated half-lives apart) pharmacokinetic study for determination of patient-specific pharmacokinetic parameters (elimination rate constant, volume of distribution at steady state, and clearance) after 30-minute infusions of gentamicin 2.8 +/- 1.6 mg/kg.

MEASUREMENTS AND RESULTS

The four nomograms evaluated were from Hartford Hospital, Barnes-Jewish Hospital, University of Rochester, and the Sanford Guide. With a pharmacokinetic analysis program and the patient-specific pharmacokinetic parameters, Cmax and minimum concentration (Cmin) were determined with use of the recommended doses and dosing intervals of the four nomograms. Also, the gentamicin dose and interval needed to achieve a Cmax and Cmin of 20 microg/ml and 0.2 microg/ml, respectively, were determined. Dosing was based on total body weight unless that weight was more than 25% of ideal body weight, in which case, an adjusted body weight was used. In general, the recommended dosages and resultant Cmax produced by the nomograms were significantly less (p < 0.05) than the dosage and Cmax actually needed to achieve a Cmax:minimum inhibitory concentration (MIC) ratio of 10 or greater for bacteria with an MIC of 2 microg/ml.

CONCLUSION

Once-daily aminoglycoside dosing using the four nomograms resulted in inaccurate dosing, and because of the large variability in human pharmacokinetics, dosing nomograms such as these should be abandoned in favor of individualizing dosages with therapeutic drug monitoring.

Extended interval aminoglycoside dosing: from concept to clinic

Extended-interval aminoglycoside dosing (EIAD), while a relatively recent concept in mainstream clinical practice, actually has its roots in the mid 1970s. Early trial and error approaches of manipulating the dosage regimen to avoid toxicity and improve efficacy have helped to characterize the pharmacodynamic properties of these drugs. The increasing successful use of EIAD and improved understanding of pharmacodynamics has helped this dosing regimen gain acceptance into routine clinical practice. A 1998 United States survey demonstrated that approximately 75% of hospitals have adopted EIAD into routine patient care. However, controversy still exists regarding some aspects of infrequent aminoglycoside administration, such as length of the drug-free interval and patient exclusion criteria. After more than 50 years of experience with the aminoglycosides we continue to learn how to most appropriately use these drugs.

In vitro pharmacodynamic analysis of single daily dosing versus conventional dosing of gentamicin administered with penicillin against Enterococcus faecalis

STUDY OBJECTIVE

To compare the effectiveness of single daily dosing (SDD) versus conventional dosing of gentamicin when administered with penicillin to treat enterococcal infections.

DESIGN

In vitro pharmacodynamic model.

SETTING

Hospital laboratory.

MEASUREMENTS AND MAIN RESULTS

A 24-hour in vitro pharmacodynamic model was employed to simulate SDD and 3 times/day dosing of gentamicin, in conjunction with continuously infused penicillin, against Enterococcus faecalis. Duplicate 24-hour kill curves were generated with varying concentrations of penicillin and gentamicin alone and in combination. No difference in the rate of kill was seen between any combination of penicillin and gentamicin. Regrowth occurred only with drug combinations in which penicillin was administered continuously at the minimum inhibitory concentration. Variations in the gentamicin dosing regimen did not affect regrowth.

CONCLUSION

In the treatment of enterococcal infections, an SDD regimen for gentamicin shows no efficacy benefit compared with conventional dosing.

Ambulatory use of parenteral antibacterials: contemporary perspectives

Outpatient parenteral antimicrobial therapy (OPAT) offers increased patient comfort and convenience in appropriately selected patients who require parenteral antibacterial therapy, as well as opportunity for cost savings. Home-based programmes, with drugs being administered by the patient or the caregiver, have become the norm in the USA. Choice of drugs for OPAT is based on antimicrobial spectrum, dosage regimen, drug stability, toxicity profile, and cost. Over the past decade, availability of sophisticated programmable pumps has allowed a wider range of antimicrobial agents to be used in the ambulatory setting. The most popular antibacterial agents in OPAT programmes in the USA are vancomycin and beta-lactams.

Gentamicin for the practicing urologist: review of efficacy, single daily dosing and "switch" therapy

PURPOSE

We review the literature on gentamicin, including single daily dosing and "switch" therapy.

MATERIALS AND METHODS

We used MEDLINE to search the literature from 1966 to June 1997, and then manually searched bibliographies to identify studies that our initial search might have missed.

RESULTS

Gentamicin has attractive characteristics, including wide spectrum, infrequent resistance, economy and familiarity. Although limited by well known toxicities, gentamicin remains a drug of choice for serious Gram-negative infections. Dosing strategies, such as single daily dosing and switch therapy, have renewed enthusiasm for this time-honored drug.

CONCLUSIONS

Gentamicin remains a valuable drug in urology. Once daily dosing and switch therapy offer the potential to increase effectiveness and convenience while decreasing toxicity and costs.

National survey of extended-interval aminoglycoside dosing

A random sample survey of 500 acute care hospitals in the United States was conducted to evaluate the adoption of extended-interval aminoglycoside dosing (EIAD). The survey revealed that EIAD has been adopted in 3 of every 4 acute care hospitals, a 4-fold increase since 1993. Of the 74.7% of hospitals reporting EIAD, 64% had written guidelines. Equal or less toxicity (87.1%), equal efficacy (76.9%), and cost-savings (65.6%) were common rationales. There has been a trend toward higher adult dosages of gentamicin (e.g., >5 mg/kg/dose) and an increase in the adoption of EIAD across all age groups (neonatal, 11%, and pediatric, 23%). Monitoring of aminoglycoside concentrations has shifted to a single determination of concentration, at 6-18 h after drug administration. The most common methods of dosage adjustment for declining renal function were an interval extension with the same dose (47%) or use of the Hartford nomogram (32%).

Advances in antimicrobial therapy

Despite several decades of improved therapy and prevention of infectious diseases, infectious pathogens remain major causes of morbidity and mortality in humans worldwide. Among the most complex and daunting problems facing medical science is the evolution of antibiotic resistance among many common and once easily-treated infectious agents. This review summarizes the status of newer antimicrobial agents that have utility against pathogens infecting the central nervous system.