Is phentermine an inhibitor of monoamine oxidase? A critical appraisal

✍ Scribed by Richard B. Rothman

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 37 KB
• Volume: 32
• Category: Article
• ISSN: 0887-4476
• DOI: 10.1002/(sici)1098-2396(199905)32:2<141::aid-syn8>3.0.co;2-r

✦ Synopsis

entitled: ''Phentermine, an unrecognized MAO inhibitor, probably increases free plasma serotonin when given with serotonin uptake blockers.'' Similar information was just published in a recent issue of Lancet (Maher et al.,1999). The authors assert that phentermine, an amphetamine analog and FDA-approved anorectic agent, inhibits MAO at therapeutic doses. Coadministration of MAO inhibitors (MAOIs) and antidepressants is contraindicated. The authors concluded, 1) that it unwise to combine phentermine with antidepressants such as fluoxetine and, 2) ''if a subject were to be treated with a drug or other drugs, (like ''Fen/Phen'') that inhibit both 5-HT uptake and MAO activity, plasma 5-HT could thus rise to unacceptable levels [which] . . . could lead to pulmonary hypertension . . . and cardiac valve lesions.'' This abstract was widely publicized without the benefit of peer review, critical commentary and sometimes without mention of important conflicts of interest. Thus, the purpose of this letter is to provide a critical review of the phentermine/MAO hypothesis.