Drug Interactions between amiodarone and stiripentol

GENERALLY AVOID: Grapefruit juice may significantly increase the plasma concentrations of orally administered amiodarone. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. In 11 nonsmoking, healthy volunteers, grapefruit juice (300 mL with drug administration, then 3 hours and 9 hours later) increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of amiodarone (17 mg/kg single dose) by 84% and 50%, respectively, compared to water. Formation of the pharmacologically active metabolite, N-desethylamiodarone (N-DEA), was completely inhibited. Clinically, this interaction can lead to altered efficacy of amiodarone, since antiarrhythmic properties of amiodarone and N-DEA appear to differ. In the study, mean increases in PR and QTc intervals of 17.9% and 11.3%, respectively, were observed 6 hours postdose with water, while increases of 10.2% and 3.3%, respectively, were observed after administration with grapefruit juice.

ADJUST DOSING INTERVAL: Food increases the rate and extent of absorption of amiodarone. The mechanism appears to involve the effect of food-induced physiologic changes on drug release from its formulation. In 30 healthy volunteers, administration of a single 600 mg dose of amiodarone following a high-fat meal resulted in a Cmax and AUC that were 3.8 and 2.4 times the respective values under fasting conditions. The time to reach peak plasma concentration (Tmax) was decreased by 37%, indicating an increased rate of absorption. Mean Cmax and AUC for the active metabolite, N-DEA, also increased by 32% and 55%, respectively, but there was no change in the Tmax.

MANAGEMENT: Patients treated with oral amiodarone should avoid consumption of grapefruits and grapefruit juice. In addition, oral amiodarone should be administered consistently with regard to meals.

GENERALLY AVOID: Taking stiripentol on an empty stomach may reduce its oral bioavailability. Stiripentol degrades rapidly when exposed to gastric acid in an empty stomach.

GENERALLY AVOID: Alcohol may potentiate the depressant effects of stiripentol on the central nervous system. Concomitant use may result in increased sedation and dizziness as well as impairment of psychomotor skills.

GENERALLY AVOID: It is not known whether stiripentol may reduce theophylline and caffeine metabolism, as data on the potential for inhibition of CYP450 1A2 are limited. Consumption of foods and nutritional products such as cola drinks (which contain significant quantities of caffeine) and chocolate (which contains caffeine and trace amounts of theophylline) may be unsafe during treatment with stiripentol, particularly in children.

MANAGEMENT: Stiripentol should be taken during a meal for optimal absorption; however, it should not be taken with milk, dairy products (e.g., yogurt, soft cream cheese), fruit juice, or carbonated beverages. Patients should be advised to avoid or limit consumption of alcohol and to avoid activities requiring mental alertness such as driving or operating hazardous machinery until they know how the medication affects them. Food and beverages that may contain caffeine or theophylline such as colas, chocolate, coffee, tea, or energy drinks should also be avoided during treatment with stiripentol.