Nelfinavir doses should be increased in infants less than 3 months

18 Jul, 2000

Authors: Litalien C. Giaquinto C. Faye A. Mechinaud F. Grosch I. Compagnucci A. Jacqz-Aigrain E.

Published in: XIII International AIDS Conference July 9th-14th 2000, Durban, South Africa. Abstract Mo PEB 2213

PENTA 7 is a phase I/II multi-centre trial to evaluate the efficacy, safety and pharmacokinetics of nelfinavir, used in combination with didanosine and stavudine in HIV-infected infants of less than three months of age.

Vertically infected infants with very high viral load appear to be more at risk for rapid disease progression and so early treatment is recommended. There has been limited paediatric pharmacokinetic research for nelfinavir, but recent data suggests that older children (age range 3 months to 13 years) need doses (mg/kg) 2 to 4 times higher than adult doses to achieve similar plasma concentrations.

In this study the initial dose of nelfinavir was 40mg/kg TID (120mg/kg), but three months after its initiation, this was increased to 75mg/kg BID (150mg/kg) after the original dose failed to achieve therapeutic levels. Also BID dosing was implemented in line with adult studies showing comparable efficacy and better adherence with this schedule in comparison with TID. In addition didanosine and stavudine were given BID at doses of 100 mg/m2 and 1mg/kg respectively.

From September 1999 to February 2000, 9 pharmacokinetic studies were performed at steady state at least 2 weeks after initiation of the therapy on patients (N=8) aged between 1.5 and 7.2 months.

Important inter-patient variability was observed for Cmin and no correlation was found between this PK parameter and either the dose or the patient’s age. Only 2 patients (aged 5.7 and 2.6 months) were considered to have the equivalent of the desired adult minimum therapeutic Cmin value (Cmin ->1000ng/ml). And among the 5 patients aged less than 4 months, only infants receiving a daily dose range of 130 to 150 mg/kg/d achieved the adult target value for AUC. Indicating that infants less than 3 or 4 months need higher doses compared to adults and older children to achieve therapeutic concentrations.