Limited information currently exists regarding interactions between HIV therapeutic agents and buprenorphine. Similar to buprenorphine, the protease inhibitors, and NNRTIs are metabolized primarily via the CYP3A4 isozyme of the cytochrome P450 system. The extent to which methadone levels decrease with induction of cytochrome P450 isoenzymes has been correlated clinically with severity of symptoms of withdrawal. Similar studies with buprenorphine are not yet available. Interactions between buprenorphine and antiretroviral agents may complicate the management of HIV disease when these medications are coadministered. In a small sample study, there was no increase in buprenorphine dosing required when co-administered with Sustiva. However, in one study with liver microsomes, ritonavir inhibited the metabolism of buprenorphine at CYP 3A4, but the clinical significance of this inhibition could not be demonstrated. It is well known that in vitro and in vivo studies do not fully correlate with one another and empiric pharmacologic interaction studies in human subjects are necessary.