Drug Interaction Report

GENERALLY AVOID: Coadministration with potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of eletriptan, which is primarily metabolized by the isoenzyme. According to the product labeling, eletriptan peak plasma concentration (Cmax) and systemic exposure (AUC) increased by nearly 3-fold and 6-fold, respectively, during coadministration with ketoconazole (400 mg). The half-life increased from 5 hours to 8 hours. Likewise, erythromycin (1000 mg) increased eletriptan Cmax by 2-fold and AUC by nearly 4-fold, while half-life increased from about 5 hours to 7 hours. Clinically, this interaction may result in increased risk of vasospastic reactions associated with the use of 5-HT1 receptor agonists, such as coronary artery vasospasm, peripheral vascular ischemia, and colonic ischemia.

MANAGEMENT: Eletriptan should not be used within at least 72 hours of treatment with potent CYP450 3A4 inhibitors. Alternatively, other 5-HT1 receptor agonists that are not metabolized by CYP450 3A4 may be considered, such as frovatriptan, naratriptan, rizatriptan, sumatriptan, and zolmitriptan.

Food enhances the oral absorption and bioavailability of tenofovir, the active entity of tenofovir disoproxil fumarate. According to the product labeling, administration of the drug following a high-fat meal increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of tenofovir by approximately 14% and 40%, respectively, compared to administration in the fasting state. However, administration with a light meal did not significantly affect the pharmacokinetics of tenofovir compared to administration in the fasting state. Food delays the time to reach tenofovir Cmax by approximately 1 hour. Tenofovir disoproxil fumarate may be administered without regard to meals.