Coadministration of Isoniazid and Antidepressant Drugs

Letter to the Editor

Sir: Isonicotinylhydrazide, also known as isoniazid, is awell-known agent for treatment of mycobacterial infections. Itis also used for prevention of tuberculosis, given 300 mg/dayfor a period of at least 6 months. In vivo studies, usingbenzylamine as substrate, have demonstrated that isoniazid intherapeutic doses inhibits plasma monoamine oxidase (MAO)with no significant effect on platelet MAO.