Combination regimens of RTV and IDV in adults offer the benefit of two potent antiretroviral agents, convenience of twice-daily dosing, unrestricted timing of meals, and fewer renal complications. There are limited, largely anecdotal data from children suggesting that initial virologic response can also be attained in children given IDV with RTV, but there are not sufficient pharmacokinetic data to define appropriate dose regimens. This study will evaluate the clinical feasibility of a combination RTV and IDV regimen for children.

Patients will be stratified on the basis of age/Tanner stage and ability to swallow intact capsules. Patients will be randomized to either Balanced Dose or Low Dose RTV treatment arms. Patients in the Balanced Dose Arm will receive RTV and IDV in approximately equal doses. The Low Dose RTV Arm will receive a dosing ratio of RTV:IDV of approximately 1:3. Patients will have scheduled study visits every 4 weeks for 6 months, then every 3 months for approximately 18 months. Study visits will consist of a medical history, physical exam, and blood and urine tests. Patients will have intensive pharmacokinetic analysis at Week 4 (or 2 weeks after a stable dose of study drugs has been reached) and Week 16. Study visits that include pharmacokinetic analysis will last 9 to 13 hours.

At each study visit, patients will be closely assessed for drug toxicity and virologic response. At the end of the study, patients with good virologic response and no evidence of toxicity may choose to enter a 48 week extension phase and continue taking the combination regimen.