Clinical ergotism induced by ritonavir.

Ritonavir strongly inhibits cytochrome P450, thus altering the metabolism of other drugs. We report on an HIV-positive man who, on his 13th day of ritonavir therapy, developed severe ergotism after self-administration of low doses of ergotamine. Drug interactions, the degree of responsibility of the patient and the availability of over-the-counter medications must be considered when prescribing antiretroviral therapy.