Phentermine Weight Loss Capsules

Mechanism of Action

Limited data are available in reference texts regarding the mechanism of action of this drug. Phentermine is an analog of methamphetamine. Similar to the amphetamines, phentermine increases the release of norepinephrine and dopamine from nerve terminals and inhibits their reuptake. Thus, phentermine is classified as an indirect sympathomimetic.[2] Other effects include a weak ability to dose-dependently raise serotonin levels, although the effect on serotonin occurs is less potent than that of methamphetamine itself.[3] Clinical effects include CNS stimulation and elevation of blood pressure. Appetite suppression is believed to occur through direct stimulation of the satiety center in the hypothalamic and limbic region.

Tolerance to the anorexiant effects of phentermine usually develops within a few weeks of starting therapy. The mechanism of tolerance appears to be pharmacodynamic in nature; higher doses of phentermine are required to produce the same response. When tolerance develops to the anorexiant effects, it is generally recommended that phentermine be discontinued rather than the dose increased.