Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 2C9 may increase the plasma concentrations of diclofenac, which is primarily metabolized by the isoenzyme. When the last dose of CYP450 2C9 inhibitor voriconazole (400 mg every 12 hours on day 1, followed by 200 mg every 12 hours on day 2) was coadministered with a single dose of diclofenac (50 mg), the peak plasma concentration (Cmax) and systemic exposure (AUC) of diclofenac increased by 114% and 78%, respectively, compared to diclofenac alone.

MANAGEMENT: Caution is advised if diclofenac is prescribed in combination with an inhibitor of CYP450 2C9. Some authorities recommend a reduction of the maximum diclofenac dose to 100 mg per day when coadministered with a CYP450 2C9 inhibitor.

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.