Mechanism of action
Phentermine is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, amphetamine (d- and d/l-amphetamine). Drugs of this class used in obesity are commonly known as “anorectics” or “anorexigenics.” It has not been established that the primary action of such drugs in treating obesity is one of appetite suppression since other central nervous system actions, or metabolic effects, may also be involved.
Pharmacodynamics
Typical actions of amphetamines include central nervous system stimulation and elevation of blood pressure. Tachyphylaxis and tolerance have been demonstrated with all drugs of this class in which these phenomena have been looked for.
Pharmacokinetics
Absorption
Following the administration of phentermine, phentermine reaches peak concentrations (Cmax) after 3 to 4.4 hours.
Drug Interactions
In a single-dose study comparing the exposures after oral administration of a combination capsule of 15 mg phentermine and 92 mg topiramate to the exposures after oral administration of a 15 mg phentermine capsule or a 92 mg topiramate capsule, there is no significant topiramate exposure change in the presence of phentermine. However in the presence of topiramate, phentermine Cmax and AUC increase 13% and 42%, respectively.
Specific Populations
Renal Impairment
Cumulative urinary excretion of phentermine under uncontrolled urinary pH conditions was 62% to 85%.
Systemic exposure of phentermine may increase up to 91%, 45%, and 22% in patients with severe, moderate, and mild renal impairment, respectively [see
Dosage and Administration (2.2) and Use in Specific Populations (8.6)
].
External links
Source: DailyMed — Phentermine ↗
Fact-sheets from PsychonautWiki. Harm-reduction reference only — not medical advice.