The impact of recent cocaine use on plasma levels of methadone and buprenorphine in patients with and without HIV-infection.

Cocaine decreases methadone and buprenorphine plasma concentrations. HIV infection and/or antiretroviral medication use may impact these relationships. We sought to determine the association between recent cocaine use and methadone and buprenorphine concentrations in HIV-infected and uninfected subjects in clinical care. R- and S-methadone or buprenorphine and norbuprenorphine concentrations were assessed at 0.5, 1, 2, and 24 hours after dosing in subjects with confirmed cocaine use and abstinence. We compared methadone and buprenorphine concentrations for cocaine use vs. abstinence, by HIV status in 16 subjects receiving methadone (6 HIV-infected) and 17 receiving buprenorphine (8 HIV-infected). With recent cocaine use, peak R-methadone (244 vs. 297 ng/mL, p = 0.03) and peak S-methadone (285 vs. 339 ng/mL); p = 0.03 concentrations were lower in HIV-uninfected subjects only. Peak buprenorphine and norbuprenorphine concentrations were unchanged regardless of cocaine use or HIV status. Cocaine may decrease methadone concentrations in HIV-uninfected subjects. HIV infection or its treatment may attenuate cocaine's effect on methadone.