PROBABLE METABOLIC INTERACTION BETWEEN METHADONE AND FLUVOXAMINE IN ADDICT PATIENTS

We report five cases where fluvoxamine (FLVX) was added to maintenance treatment with methadone (MTD) in addict patients with affective diso rders. In view of the implication of FLVX in several metabolic drug in teractions, MTD plasma levels were measured before and after treatment with FLVX. A slight increase (similar to 20% of the MTD plasma level/ dose ratio) occurred in two cases. In the remaining three patients, th e interaction was more pronounced (40-100% increase of the MTD plasma level/dose ratio), with clinical manifestations of opiate withdrawal a fter stopping FLVX therapy in one case. Caution is needed when startin g or stopping treatment with FLVX in patients receiving maintenance tr eatment with methadone.