Carbamazepine–Indinavir Interaction Causes Antiretroviral Therapy Failure

OBJECTIVE:To report a case of antiretroviral therapy failure caused by an interaction between carbamazepine and indinavir.CASE SUMMARY:A 48-year-old HIV-positive white man was treated with antiretroviral triple therapy, consisting of indinavir, zidovudine, and lamivudine. His HIV-RNA (viral load) became undetectable (<400 copies/mL) less than two months after this therapy was started; this was confirmed one month later. Shortly after the start of antiretroviral therapy, the patient developed herpes zoster, which was treated with famciclovir. Tramadol was initially prescribed for postherpetic neuralgia; however, this was substituted with carbamazepine due to insufficient analgesic effect. Indinavir plasma concentrations decreased substantially during carbamazepine therapy. Carbamazepine was stopped after 2.5 months and, two weeks later, the HIV-RNA was detectable (6 times 103 copies/mL). Resistance for lamivudine was observed in that blood sample; resistance for zidovudine might have been present, and resi...