Class: Centrally Acting Appetite Suppressant. C-IV
Dosage Forms. Capsule: 15 mg, 30 mg, 37.5 mg; Tablet: 37.5 mg; Dispersible Tablet: 15 mg, 30 mg, 37.5 mg
Common FDA Label Indication, Dosing, and Titration.
1. Simple obesity, short-term treatment: 15-37.5 mg (capsules) or 37.5 mg (tablets) po daily either before breakfast or 1-2 h after breakfast; may titrate to response
Off-Label Uses. None
MOA. Phentermine is a sympathomimetic amine with pharmacologic activity similar to amphetamines. Actions include central nervous system stimulation and elevation of blood pressure. Weight loss is due to anorectic effect, primarily one of appetite suppression, but may also have other CNS or metabolic effects.
Drug Characteristics: Phentermine
Medication Safety Issues: Phentermine
Drug Interactions: Phentermine
Adverse Reactions: Phentermine
Efficacy Monitoring Parameters. Weight loss.
Toxicity Monitoring Parameters. Signs and symptoms of heart valve disorders and primary pulmonary hypertension, ECG, BP.
Key Patient Counseling Points. Phentermine may impair the ability of the patient to engage in potentially hazardous activities such as operating machinery or driving a motor vehicle; the patient should therefore be cautioned accordingly.
Clinical Pearls. Phentermine is indicated only as short-term monotherapy for the management of exogenous obesity. The safety and efficacy of combination therapy with phentermine and any other drug products for weight loss, including SSRIs, have not been established. Primary pulmonary hypertension and valvular heart disease have been reported to occur in patients receiving a combination of phentermine with fenfluramine or dexfenfluramine and should be avoided. Tolerance to the anorectic effect usually develops within a few weeks. When this occurs, the recommended dose should not be exceeded in an attempt to increase the effect; rather, the drug should be discontinued.