Adverse consequences of fluoxetine-MAOI combination therapy.

The authors describe two series of patients: 12 treated simultaneously with fluoxetine and a monoamine oxidase inhibitor and 6 patients started on treatment with an MAOI 10 days or more after stopping fluoxetine treatment. All patients had extremely refractory depression and were treated in open fashion before general knowledge was obtained of the side effects that may accompany the fluoxetine-MAOI combination. During the fluoxetine-MAOI trial, most patients continued to receive other psychotropic combinations that had been partially helpful. The use of fluoxetine and an MAOI, either together or in close succession, was accompanied by a very high incidence of adverse effects, especially the "serotonergic syndrome." This syndrome was characterized by mental status changes, such as hypomania and confusion, and physical symptoms, such as myoclonus, hypertension, tremor, and diarrhea. Because of the high incidence of side effects and the lack of definite efficacy, the concurrent use of fluoxetine and MAOIs should generally be avoided. The long half-lives of fluoxetine and norfluoxetine, as well as the prolonged metabolic effects of MAOIs, may also dispose patients to an interaction if one of the drugs is started soon after stopping the other.