Drug Interaction Report

Coadministration with pretomanid may reduce the plasma concentration of midazolam. The mechanism of this interaction is unknown but may involve minimal induction (approximately 20%) of CYP450 3A metabolism. In a study of 14 healthy volunteers, who were administered 400 mg/day (double the recommended dose) pretomanid for 14 days and a single 2 mg oral dose of midazolam on day 14 resulted in a decrease in midazolam mean systemic exposure (AUC) by 15% and mean peak plasma concentration (Cmax) by 16%. An increase in 1-hydroxy midazolam mean AUC by 14% and Cmax by 5% was also observed. These changes were not considered clinically significant.

GENERALLY AVOID: The pharmacologic activity of oral midazolam, triazolam, and alprazolam may be increased if taken after drinking grapefruit juice. The proposed mechanism is CYP450 3A4 enzyme inhibition. In addition, acute alcohol ingestion may potentiate CNS depression and other CNS effects of many benzodiazepines. Tolerance may develop with chronic ethanol use. The mechanism may be decreased clearance of the benzodiazepines because of CYP450 hepatic enzyme inhibition. Also, it has been suggested that the cognitive deficits induced by benzodiazepines may be increased in patients who chronically consume large amounts of alcohol.

MANAGEMENT: The manufacturer recommends that grapefruit juice should not be taken with oral midazolam. Patients taking triazolam or alprazolam should be monitored for excessive sedation. Alternatively, the patient could consume orange juice which does not interact with these drugs. Patients should be advised to avoid alcohol during benzodiazepine therapy.

GENERALLY AVOID: Coadministration with alcohol may increase the risk of hepatotoxicity associated with the use of combination drug regimens that include pretomanid.

ADJUST DOSING INTERVAL: Food enhances the oral bioavailability of pretomanid. The mechanism has not been reported. Compared with the fasted state, oral administration of pretomanid with a high-fat, high-calorie meal (approximately 150, 250, and 500 to 600 calories from protein, carbohydrate, and fat, respectively) increased mean systemic exposure (AUC) and peak plasma concentration (Cmax) of pretomanid by 88% and 76%, respectively.

MANAGEMENT: Patients should avoid alcohol use during treatment with pretomanid. In addition, to ensure maximal oral absorption, pretomanid should be administered with food. Tablets should be swallowed whole.