Aminoglycoside and vancomycin serum concentration monitoring and mortality due to neonatal sepsis in Saudi Arabia

Population Pharmacokinetic Models of Vancomycin in Paediatric Patients: A Systematic Review

BACKGROUND

Vancomycin is commonly used to treat gram-positive bacterial infections in the paediatric population, but dosing can be challenging. Population pharmacokinetic (popPK) modelling can improve individualization of dosing regimens. The primary objective of this study was to describe popPK models of vancomycin and factors that influence pharmacokinetic (PK) variability in paediatric patients.

METHODS

Systematic searches were conducted in the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, International Pharmaceutical Abstracts and the grey literature without language or publication status restrictions from inception to 17 August 2020. Observational studies that described the development of popPK models of vancomycin in paediatric patients (< 18 years of age) were included. Risk of bias was assessed using the National Heart, Lung and Blood Institute Study Quality Assessment Tool for Case Series Studies.

RESULTS

Sixty-four observational studies (1 randomized controlled trial, 13 prospective studies and 50 retrospective studies of 9019 patients with at least 25,769 serum vancomycin concentrations) were included. The mean age was 2.5 years (range 1 day-18 years), serum creatinine was 47.1 ± 33.6 µmol/L, and estimated creatinine clearance was 97.4 ± 76 mL/min/1.73m². Most studies found that vancomycin PK was best described by a one-compartment model (71.9%). There was a wide range of clearance and volume of distribution (V_d) values (range 0.014-0.27 L/kg/h and 0.43-1.46 L/kg, respectively) with interindividual variability as high as 49.7% for clearance and 136% for V_d, proportional residual variability up to 37.5% and additive residual variability up to 17.5 mg/L. The most significant covariates for clearance were weight, age, and serum creatinine or creatinine clearance, and weight for V_d. Variable dosing recommendations were suggested.

CONCLUSION

Numerous popPK models of vancomycin were derived, however external validation of suggested dosing regimens and analyses in subgroup paediatric populations such as dialysis patients are still needed before a popPK model with best predictive performance can be applied for dosing recommendations. Significant intraindividual and interindividual PK variability was present, which demonstrated the need for ongoing therapeutic drug monitoring and derivation of PK models for vancomycin for certain subgroup populations, such as dialysis patients.

Usage Pattern and Serum Level Measurement of Amikacin in the Internal Medicine Ward of the Largest Referral Hospital in the South of Iran: A Pharmacoepidemiological Study

BACKGROUND

The inappropriate use of aminoglycosides has harmful effects such as the development of resistant pathogens and the incidence of nephrotoxicity and ototoxicity. Therefore, drug utilization evaluation of these drugs may improve their usage remarkably. The aim of this study was to assess the usage pattern of amikacin in an internal medicine ward.

METHODS

This cross-sectional study was conducted in the Internal Medicine Ward of Nemazee Teaching Hospital, Shiraz, Iran, in 2011. The guideline for amikacin use was approved by the institutional Pharmacy and Therapeutics Committee, and the study criteria were developed to assess several parameters involved in amikacin therapy such as appropriateness of drug use, dosage, duration of therapy, toxicity monitoring, and serum concentration assay. Serum concentration was assayed using a Cobas Mira AutoAnalyzer. Clinical and paraclinical parameters such as glomerular filtration rate, culture, microbial sensitivity, white blood cell count, and fever were collected.

RESULTS

Sixty-three patients were evaluated. Fifty-seven percent of the patients needed dose readjustment; however, it was not performed for 89% of them. Culture between 48 and 72 hours after amikacin administration was not controlled for 79% of the patients. In 19% of the patients, optimum therapeutic effect was not achieved. The mean±SD of the trough and peak concentrations was 7.63±5.4 μg/mL and 15.67±7.79 μg/mL, respectively. Forty-five percent of the trough and 38% of the peak levels were within the therapeutic range. The overall adherence of amikacin usage to the guideline was only 48%.

CONCLUSION

To achieve appropriate treatment and prevent toxic effects, we recommend that pharmacokinetic dosing methods, amikacin guideline, and serum monitoring be considered.

Bacteremia in children: epidemiology, clinical diagnosis and antibiotic treatment

The diagnosis of bacteremia in children is important and it can be clinically challenging to recognize the signs and symptoms. The reported rates of bacteremia are higher in young children but with the increasing vaccine coverage, there has been a decrease in bacteremia due to the three vaccine preventable bacteria (Streptococcus pneumoniae, Haemophilus influenzae group b and Neisseria meningitidis). Notably, there have been increases in healthcare-associated bacteremias with a rise in Staphylococcus aureus and Gram negative bacteremias. This review provides a brief overview of the clinical diagnosis of bacteremia in children, focusing on the epidemiology, clinical characteristics, risk factors, antibiotic treatment, outcomes and preventative measures to reduce the incidence of bacteremia and improve morbidity and mortality.

Considerations in the pharmacologic treatment and prevention of neonatal sepsis

The management of neonatal sepsis is challenging owing to complex developmental and environmental factors that contribute to inter-individual variability in the pharmacokinetics and pharmacodynamics of many antimicrobial agents. In this review, we describe (i) the changing epidemiology of early- and late-onset neonatal sepsis; (ii) the pharmacologic considerations that influence the safety and efficacy of antibacterials, antifungals, and immunomodulatory adjuvants; and (iii) the recommended dosing regimens for pharmacologic agents commonly used in the treatment and prevention of neonatal sepsis. Neonatal sepsis is marked by high morbidity and mortality, such that prompt initiation of antimicrobial therapy is essential following culture collection. Before culture results are available, combination therapy with ampicillin and an aminoglycoside is recommended. When meningitis is suspected, ampicillin and cefotaxime may be considered. Following identification of the causative organism and in vitro susceptibility testing, antimicrobial therapy may be narrowed to provide targeted coverage. Therapeutic drug monitoring should be considered for neonates receiving vancomycin or aminoglycoside therapies. For neonates with invasive fungal infections, the development of new antifungal agents has significantly improved therapeutic outcomes in recent years. Liposomal amphotericin B has been found to be safe and efficacious in patients with renal impairment or toxicity caused by conventional amphotericin B. Antifungal prophylaxis with fluconazole has also been reported to dramatically reduce rates of neonatal invasive fungal infections and to improve long-term neurodevelopmental outcomes among treated children. Additionally, several large multicenter studies are currently investigating the safety and efficacy of oral lactoferrin as an immunoprophylactic agent for the prevention of neonatal sepsis.

Therapeutic drug monitoring of aminoglycosides in neonates

The efficacy and toxicity of aminoglycosides show a strong direct positive relationship with blood drug concentrations, therefore, therapy with aminoglycosides in adults is usually guided by therapeutic drug monitoring. Dosing regimens in adults have evolved from multiple daily dosing to extended-interval dosing. This evolution has also taken place in neonates. Neonates, however, display large interindividual differences in the pharmacokinetics of aminoglycosides due to developmental differences early in life. The volume of distribution of aminoglycosides shows a strong relationship with bodyweight, which tends to be larger (corrected for bodyweight) in more premature infants and those with sepsis. Renal clearance of aminoglycosides increases with gestational age and accelerates immediately after birth. Because of these developmental influences, there is great inter- and intraindividual variability in the volume of distribution and clearance of these drugs, and investigators have established aminoglycoside dosing regimens based on bodyweight and/or gestational age. Widely practised dosing regimens comprise 4-5 mg/kg bodyweight of gentamicin every 24-48 hours as a first dose, followed by dose adjustment based on therapeutic drug monitoring. Although formal toxicity studies are scarce, there is no evidence that aminoglycoside toxicity in neonates differs from that in adults. Monitoring of blood drug concentrations and intelligent reconstruction of individual pharmacokinetic behaviour using a population pharmacokinetic model, optimally chosen blood sampling times and appropriate pharmacokinetic software, help clinicians to quickly optimize aminoglycoside dosing regimens to maximize the clinical effect and minimize the toxicity of these drugs.