Interaction between levothyroxine and indinavir in a patient with HIV infection.

Drug interactions are an important and emerging problem in the treatment of HIV-infected patients. Protease inhibitors, like nonnucleoside reverse transcriptase inhibitors, are metabolized by the cytochrome P-450 enzyme system and each of these antiretroviral agents may interact with other drugs metabolized by this system. Some protease inhibitors may also interact with glucuronosyl transferase activity affecting plasma concentrations of drugs metabolized through this pathway. We describe a case of an HIV-infected patient, taking levothyroxine for hypothyroidism and clinically stable, who, after the introduction of an antiretroviral regimen containing indinavir, developed a pharmacological hyperthyroidism.