If you have a prescription drug book, it will say under any SSRI medication like Zoloft, Prozac, Celexa, Paxil, Wellbutrin, etc that this is dangerous when combined with a MAO inhibitor. But if a lot of people are like me, they have tried phentermine, Ionimin, Fastin, Adipex-P for weight loss and these are MAO inhibitors. Fortunately, I'm no longer trying weight loss drugs. But why doesn't anyone tell us these things when we need to know them!?


Biochem Pharmacol 2000 Jun 15;59(12):1611-21

Characterization of phentermine and related compounds as monoamine oxidase (MAO) inhibitors.

Ulus IH, Maher TJ, Wurtman RJ.

Department of Pharmacology and Clinical Pharmacology, Uludag University Medical School, Bursa, Turkey.

Phentermine was shown in the 1970s to inhibit the metabolism of serotonin by monoamine oxidase (MAO), but never was labeled as an MAO inhibitor; hence, it was widely used in combination with fenfluramine, and continues to be used, in violation of their labels, with other serotonin uptake blockers. We examined the effects of phentermine and several other unlabeled MAO inhibitors on MAO activities in rat lung, brain, and liver, and also the interactions of such drugs when administered together. Rat tissues were assayed for MAO-A and -B, using serotonin and beta-phenylethylamine as substrates. Phentermine inhibited serotonin-metabolizing (MAO-A) activity in all three tissues with K(i) values of 85-88 microM. These potencies were similar to those of the antidepressant MAO inhibitors iproniazid and moclobemide. When phentermine was mixed with other unlabeled reversible MAO inhibitors (e.g. pseudoephedrine, ephedrine, norephedrine; estradiol benzoate), the degree of MAO inhibition was additive. The cardiac valvular lesions and primary pulmonary hypertension that have been reported to be associated with fenfluramine-phentermine use may have resulted from the intermittent concurrent blockage of both serotonin uptake and metabolism.