Drug Interaction Report

MONITOR: Coadministration with oritavancin may increase the plasma concentrations of drugs that are substrates of CYP450 2C9, and/or 2C19. The mechanism is decreased clearance due to inhibition of these isoenzymes by oritavancin. In a screening drug interaction study in 16 healthy volunteers, a single 1,200 mg dose of oritavancin increased the omeprazole-to-5-hydroxyomeprazole plasma ratio by 15% and the systemic exposure (AUC) of warfarin by 31%, indicating weak inhibition of CYP450 2C19 and CYP450 2C9, respectively.

MANAGEMENT: Caution is advised when oritavancin used concomitantly with drugs that are substrates of CYP450 2C9 and/or 2C19, particularly sensitive substrates, or those with a narrow therapeutic range. Dosage adjustments as well as closer clinical and laboratory monitoring for the development of adverse effects may be appropriate for some drugs whenever oritavancin is added to or withdrawn from therapy. Individual product labeling should be consulted for further guidance.

GENERALLY AVOID: The concurrent use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol may lead to gastrointestinal (GI) blood loss. The mechanism may be due to a combined local effect as well as inhibition of prostaglandins leading to decreased integrity of the GI lining.

MANAGEMENT: Patients should be counseled on this potential interaction and advised to refrain from alcohol consumption while taking aspirin or NSAIDs.

MONITOR: Coadministration of two or more sympathomimetic agents may increase the risk of adverse effects such as nervousness, irritability, and increased heart rate. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic agents. Additive increases in blood pressure and heart rate may occur due to enhanced peripheral sympathetic activity.

MANAGEMENT: Caution is advised if two or more sympathomimetic agents are coadministered. Pulse and blood pressure should be closely monitored.