Drug Interactions between phentermine and pramlintide

GENERALLY AVOID: Alcohol may potentiate the central nervous system and cardiovascular effects of centrally-acting appetite suppressants. In one study, concurrent administration of methamphetamine (30 mg intravenously) and ethanol (1 gm/kg orally over 30 minutes) increased heart rate by 24 beats/minute compared to methamphetamine alone. This increases cardiac work and myocardial oxygen consumption, which may lead to more adverse cardiovascular effects than either agent alone. Subjective effects of ethanol were diminished in the eight study subjects, but those of methamphetamine were not affected. The pharmacokinetics of methamphetamine were also unaffected except for a decrease in the apparent volume of distribution at steady state.

MANAGEMENT: Concomitant use of centrally-acting appetite suppressants and alcohol should be avoided if possible, especially in patients with a history of cardiovascular disease. Patients should be counselled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

ADJUST DOSING INTERVAL: Pramlintide slows gastric emptying and may delay the absorption of concomitantly administered oral medications. In a pharmacokinetic study of 24 patients with type 2 diabetes, coadministration with pramlintide (120 mcg) decreased the peak plasma concentration (Cmax) of acetaminophen (1000 mg) by 29% and increased its time to peak plasma concentration (Tmax) based on the time of acetaminophen administration relative to pramlintide injection. Pramlintide significantly increased acetaminophen Tmax (range 48 to 72 minutes) when acetaminophen was administered simultaneously with or up to 2 hours following pramlintide injection, but it had negligible effect when acetaminophen was administered 1 to 2 hours before pramlintide injection.

MANAGEMENT: When rapid onset of a concomitantly administered oral medication is critical to its effectiveness, the medication should be administered at least 1 hour before or 2 hours after pramlintide injection.