Drug Interactions between fenfluramine and Relistor

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: Food may reduce the rate and extent of absorption of methylnaltrexone following oral administration. When a single 450 mg oral dose of methylnaltrexone was administered with a high-fat breakfast (approximately 800 to 1000 calories; 60% from fat, 25% from carbohydrate, and 15% from protein) in healthy study subjects, methylnaltrexone peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 60% and 43%, respectively, while time to reach Cmax delayed by 2 hours.

MANAGEMENT: Oral methylnaltrexone should be taken with water on an empty stomach at least 30 minutes before the first meal of the day.