Therapeutic Drug Monitoring and Viral Resistance Testing in the Treatment of HIV-Infected Children

This study will evaluate a new treatment strategy called therapeutic drug monitoring (TDM) in HIV-infected children and adolescents. TDM involves analyzing the virus, giving drugs the virus is most sensitive to, monitoring drug blood levels to make sure there is enough drug to work against the virus, and changing the drug dose if it is too low. HIV-infected children between 0 and 21 years of age who may benefit from treatment with a protease inhibitor and who are not benefiting from their current antiretroviral drug treatment regimen may be enrolled in this 48-week study. Patients who are not currently receiving antiretroviral treatment, including patients who have never received antiretroviral treatment, may be enrolled in the study. Participants will have blood drawn to learn what anti-HIV drugs the patient's virus is resistant to-that is, what drugs are no longer effective against the virus. This is determined by analyzing the virus's genotype (detailed genetic structure) and phenotype (response to exposure to anti-viral drugs). Based on these test results and the patient's prior medication history, a drug regimen tailored to the individual patient will be prescribed. It may include one or two nucleoside reverse transcriptase inhibitors, such as zidovudine, didanosine, lamuvidine, zalcitabine, stavudine), a non- nucleoside reverse transcriptase inhibitor such as nevirapine or efavirenz, and a protease inhibitor such as amprenavir, nelfinavir, saquinavir, ritonavir, or Kaletra (a combination of lopinavir and ritonavir). After the patients begin treatment, the amount of the protease inhibitor in the blood will be measured. If not enough of the drug is found in the blood, the dose of the drug will be increased and the amount of the drug in the blood will be checked again. In this study, the dose may be increased up to three times. Patients will be seen in clinic for 6 days when treatment begins to measure blood levels of the medicines and evaluate the response o