To date the combination of indinavir boosted with ritonavir (indinavir/ritonavir) is one of the least expensive protease inhibitor based HAART regimen in Thailand and in several other resource limited settings. The main objective of this study was to assess and compare the pharmacokinetics of 600mg indinavir /100mg ritonavir bid versus 400mg indinavir /100mg ritonavir bid as part of the HAART regimen of zidovudine (ZDV), lamivudine (3TC), indinavir (IDV) and ritonavir (RTV) in Thai patients. It was found that reduced doses of indinavir/ritonavir maintained adequate indinavir plasma levels compared to current guidelines suggesting that these doses are efficacious in this setting. Considering the poor tolerability of 600 mg of indinavir, the 400 mg of indinavir may be preferred due to its lower exposure indices.

For further information please refer to: Pharmacokinetic Study of Indinavir Drug Levels When Boosted With Ritonavir in Thailand [clinicaltrials.gov]

Despite its widespread use and published guidelines, the optimal dose for zidovudine is unknown. In Thailand, zidovudine 300 mg twice daily has been frequently associated with gastrointestinal intolerance and anemia. Excessive zidovudine drug exposure may explain the poor tolerability of the dose of 300 mg twice daily, especially in patients with low body weights. concentrations are informative. It was found that zidovudine 200 mg twice daily in patients less than 60 kg achieved similar efficacy to 300 mg twice daily in heavier patients and was well tolerated in the long term.

For further information please refer to: Intensive pharmacokinetics of zidovudine 200 mg twice daily in HIV-1-infected patients weighing less than 60 kg on highly active antiretroviral therapy. [pubmed.gov]

The optimum strategy for stopping treatment with drugs that have different half-lives in a combination regimen to minimize the risk of selecting drug-resistant viruses remains unknown. We evaluated drug concentrations in plasma, HIV load and development of drug resistance after a planned treatment interruption NNRTI containing regimen in HIV infected children. It was found that in children with virological suppression who experienced interruption of treatment with an NNRTI stopping strategies were not associated with the selection of NNRTI resistance mutations.

For further information please refer to: Plasma drug concentrations and virologic evaluations after stopping treatment with nonnucleoside reverse-transcriptase inhibitors in HIV type 1-infected children. [pubmed.gov]