Pharmacokinetics of the Protease Inhibitor Indinavir in Human Immunodeficiency Virus Type 1-Infected Children

ABSTRACT The objective of this study was to evaluate the pharmacokinetics of indinavir in human immunodeficiency virus-infected children as part of a prospective, open, uncontrolled, multicenter study in The Netherlands. Human immunodeficiency virus type 1-infected children were monitored over 6 months of treatment with zidovudine (120 mg/m2 every 8 h [q8h]), lamivudine (4 mg/kg of body weight q12h), and indinavir (33mg/kg of metabolic weight [MW] q8h). Four weeks after the start of treatment, the steady-state pharmacokinetics of indinavir were determined by high-pressure liquid chromatography. If patients had an indinavir area under the concentration-time curve (AUC) of below 10 or above 30 mg/liter · h, a dose increase or a dose reduction was made and pharmacokinetic measurements were repeated 4 weeks later. Nineteen patients started with the dose of 33 mg/kg of MW q8h. The median AUC (range) was 10.5 (2.8 to 51.0) mg/liter · h. The median AUC (range) in 17 children treated with 50 mg/kg of MW q8h was 20.6 (4.1 to 38.7) mg/liter · h. Finally, five patients had a dose increase to 67 mg/kg of MW q8h, resulting in a median AUC (range) of 36.6 (27.2 to 80.0) mg/liter · h. After 6 months of treatment, there were 11 children with an AUC of below 20 mg/liter · h, of whom 5 (45%) had a detectable viral load, while this was the case in none of the 11 children with an AUC of higher than 20 mg/liter · h. We conclude that the optimal dose of indinavir in children to obtain drug exposure similar to that observed in adult patients is 50 mg/kg of MW q8h, which approximates 600 mg/m2 q8h. It would even be better to adjust the indinavir dose based on an AUC of greater than 20 mg/liter · h.