<p>Co-administration of different antifungals, macrolide antibiotics, CNS depressant drugs like ketoconazole, itraconazole, troleandomycin, clarithromycin, nelfinavir, and nefazadone may enhance or prolong the effects of Fentanyl. The concomitant use of amprenavir, aprepitant, diltiazem, erythromycin, fluconazole, fosamprenavir, grapefruit juice, and verapamil with Fentanyl may also result in an increase in Fentanyl plasma concentrations, which could increase or prolong adverse drug effects and may cause potentially fatal respiratory depression.</p>