Pharmacocinétique comparée des aminosides utilisés en dose unique journalière

Pharmacokinetics of once-daily amikacin in pediatric patients

OBJECTIVE: To study the pharmacokinetic parameters of a once-daily regimen of amikacin (15 mg/kg) in association with other antimicrobial agents in 35 children with severe Gram-negative infections. METHODS: A Bayesian approach was developed to optimize the amikacin regimen. The predictive performance was assessed by computing bias and precision. Each patient was evaluated for toxicity after 5 days of treatment. RESULTS: Peak amikacin concentrations on days 2 and 5 of therapy averaged 31.3 plus minus 9.0 mg/L and 32.4 plus minus 7.4 mg/L, respectively. To achieve peak serum concentrations between 30 and 40 mg/L, individualized dosage was necessary in 19 of 35 children. The pharmacokinetic parameters showed large interindividual variations, with a mean half-life of 2 h and a mean volume of distribution of 0.36 L/kg. No nephrotoxicity was observed in any of the children. After individualization of dosage on the basis of one measurement of peak concentration, no significant differences were observed between predicted and subsequently measured amikacin concentrations. CONCLUSIONS: Once-daily dosage of amikacin (15 mg/kg) is well tolerated in pediatric patients; however, a loading dose of 20 mg/kg is recommended to achieve a therapeutic peak value between 30 and 40 mg/L. Initial serum monitoring is essential in a population such as children, with wide interpatient variability. Using the Bayesian approach, the amikacin regimen in children can then be predicted with minimal bias and good precision.

Aminoglycosides

Despite their nephrotoxic and ototoxic side effects, AG remain useful antibiotics because of their major, rapid, and dose-dependent bactericidal effects. Combination therapy with an AG appears particularly important in neutropenic and other high-risk patients to provide broad-spectrum bactericidal activity, synergism, and reduction of emergence of resistant pathogens. OD AG therapy is associated with high peak levels in serum that maintain efficacy and low-to-undetectable trough levels in serum that attenuate the risk of toxicity. Administration of short-term OD AG therapy to patients not at risk without renal impairment may not absolutely require dosing monitoring. This therapeutic strategy has been proved useful in clinical trials, now including febrile episodes in neutropenic patients, but it should be avoided during infections in which antimicrobial synergism is required, such as enterococcal endocarditis.