Does Buspar Reduce The Effectiveness Of Phentermine?

In our latest question and answer, the pharmacist discusses the potential interaction and effects of taking Buspar (buspirone) with Adipex-P (Phentermine).

Jan 05, 2018

Carneg02 asked

How does taking Buspar (buspirone) hcl 5mg with adipex affect your weight?

Answer

Buspar (buspirone) is a non-benzodiazepine anti-anxiolytic medication that generally does not impair motor function, and is not associated with pronounced or physical dependence. In terms of its effects on weight, it is generally recognized as "weight neutral", and doesn't influence significant weight gain or loss in most individuals.

Having said that, possible weight change is listed as a rare side effect for Buspar as is appetite stimulation. Per the package insert for Buspar, the following were listed as rare GI side effects:

Rare Buspar GI Side Effects (0.1%-1% Incidence)
  • Flatulence
  • Anorexia
  • Appetite stimulation
  • Weight gain
  • Weight loss
  • Hypersalivation

The likely mechanism of Buspar affecting weight (although uncommon) is most likely mediated by its effects of the neurotransmitter serotoinin.

There is not considered to be an interaction between Buspar and Adipex-P (phentermine). Theoretically, if you do experience weight fluctuation on Buspar, that could influence how effective phentermine appears to be, but again, Buspar should not directly affect the actions of phentermine.

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