[Interferon alpha-associated agranulocytosis during clozapine treatment. Case report and status of current knowledge].

Little is known about possibilities of chronic hepatitis C treatment with interferon-alpha (IFN-alpha) in psychiatric patients continuously taking antipsychotics. We report on a 28-year-old hepatitis C-positive man with paranoid psychosis. He was successfully treated with clozapine, an atypical antipsychotic drug which is known for the risk of granulocytopenia and agranulocytosis. With doses up to 200 mg/day over 3 years, he showed no remarkable changes in WBC. Because of the chronic hepatitis C with genotype 3a, additional treatment was started with IFN-alpha (s.c., 3 x 6 million IU/week). After 2 months of therapy he developed a severe agranulocytosis. Both clozapine and IFN-alpha were discontinued, and his WBC returned to normal. Results from bone marrow examination were compatible with a toxic reaction possibly caused by either or both medications. We discuss possible problems with IFN-alpha during the treatment of psychiatric patients, interactions with psychiatric medication, and hematotoxic side effects like those from clozapine. We recommend combining IFN-alpha with less "toxic" antipsychotics and weekly checks of WBC.