Drug Interaction Report

ADJUST DOSE: Coadministration with inhibitors of CYP450 3A4 may increase the plasma concentrations of eplerenone, which is primarily metabolized by the isoenzyme. In pharmacokinetic studies, administration of a single 100 mg dose of eplerenone in combination with the potent CYP450 3A4 inhibitor ketoconazole (200 mg twice a day) resulted in a 1.7-fold increase in eplerenone peak plasma concentration (Cmax) and a 5.4-fold increase in systemic exposure (AUC), while administration with moderate inhibitors (erythromycin 500 mg twice daily; verapamil 240 mg once daily; saquinavir 1200 mg three times daily; fluconazole 200 mg once daily) resulted in increases in eplerenone Cmax ranging from 1.4- to 1.6-fold and AUC from 2.0- to 2.9-fold.

MANAGEMENT: When used with moderate CYP450 3A4 inhibitors, the initial dosage of eplerenone should be reduced to 25 mg once daily for the treatment of hypertension. Patients already on eplerenone who start treatment with a moderate CYP450 3A4 inhibitor should have serum potassium and creatinine checked in 3 to 7 days.

GENERALLY AVOID: Coadministration with grapefruit juice may increase the plasma concentrations of eplerenone. The primary mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. Inhibition of hepatic CYP450 3A4 may also contribute. In drug interaction studies, administration of a single 100 mg dose of eplerenone in combination with grapefruit juice resulted in a 25% increase in eplerenone systemic exposure (AUC). High blood levels of eplerenone can increase the risk of side effects including hyperkalemia. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition.

MANAGEMENT: It may be advisable for patients to avoid the consumption of grapefruit, grapefruit juice, or supplements that contain grapefruit during treatment with eplerenone.

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.