title: Is the recommended dose of efavirenz optimal in young West African human immunodeficiency virus-infected children?
abstract: We aimed in this study to describe efavirenz concentration-time courses in treatment-naïve children after once-daily administration to study the effects of age and body weight on efavirenz pharmacokinetics and to test relationships between doses, plasma concentrations, and efficacy. For this purpose, efavirenz concentrations in 48 children were measured after 2 weeks of didanosine-lamivudine-efavirenz treatment, and samples were available for 9/48 children between months 2 and 5 of treatment. Efavirenz concentrations in 200 plasma specimens were measured using a validated high-performance liquid chromatography method. A population pharmacokinetic model was developed with NONMEM. The influence of individual characteristics was tested using a likelihood ratio test. The estimated minimal and maximal concentrations of efavirenz in plasma (Cmin and Cmax, respectively) and the area under the concentration-time curve (AUC) were correlated to the decrease in human immunodeficiency virus type 1 RNA levels after 3 months of treatment. The threshold Cmin (and AUC) that improved efficacy was determined. The target minimal concentration of 4 mg/liter was considered for toxicity. An optimized dosing schedule that would place the highest percentage of children in the interval of effective and nontoxic concentrations was simulated. The pharmacokinetics of efavirenz was best described by a one-compartment model with first-order absorption and elimination. The mean apparent clearance and volume of distribution for efavirenz were 0.211 liter/h/kg and 4.48 liters/kg, respectively. Clearance decreased significantly with age. When the recommended doses were given to 46 of the 48 children, 19% (44% of children weighing less than 15 kg) had C(min)s below 1 mg/liter. A significantly higher percentage of children with C(min)s of >1.1 mg/liter or AUCs of >51 mg/liter x h than of children with lower values had viral load decreases greater than 2 log10 copies/ml after 3 months of treatment. Therefore, to optimize the percentage of children with C(min)s between 1.1 and 4 mg/liter, children should receive the following once-daily efavirenz doses: 25 mg/kg of body weight from 2 to 6 years, 15 mg/kg from 6 to 10 years, and 10 mg/kg from 10 to 15 years. These assumptions should be prospectively confirmed.
authors.affiliation: EA3620, Université Paris-Descartes, Paris, France. deborah.hirt@univ-paris5.fr
authors.forename: Déborah
authors.initials: D
authors.lastname: Hirt
authors.forename: Saik
authors.initials: S
authors.lastname: Urien
authors.forename: Mathieu
authors.initials: M
authors.lastname: Olivier
authors.forename: Hélène
authors.initials: H
authors.lastname: Peyrière
authors.forename: Boubacar
authors.initials: B
authors.lastname: Nacro
authors.forename: Serge
authors.initials: S
authors.lastname: Diagbouga
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Zoure
authors.forename: François
authors.initials: F
authors.lastname: Rouet
authors.forename: Hervé
authors.initials: H
authors.lastname: Hien
authors.forename: Philippe
authors.initials: P
authors.lastname: Msellati
authors.forename: Philippe
authors.initials: P
authors.lastname: Van De Perre
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Tréluyer
mesh_terms: D000293:Adolescent; D000480:Alkynes; D019380:Anti-HIV Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D048588:Benzoxazines / Q000008:administration & dosage* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D003521:Cyclopropanes; D004334:Drug Administration Schedule; D005260:Female; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D008297:Male
chemical_list: D000480:Alkynes; D019380:Anti-HIV Agents; D048588:Benzoxazines; D003521:Cyclopropanes; C098320:efavirenz