Drug Interactions between dihydrocodeine / phenylephrine and idelalisib

GENERALLY AVOID: Coadministration with idelalisib may increase the plasma concentrations of drugs that are substrates of CYP450 3A4. Idelalisib has been shown to be a potent inhibitor of this isoenzyme. In healthy volunteers, administration of a single 5 mg dose of midazolam, a CYP450 3A4 probe substrate, with idelalisib 150 mg for 15 doses increased mean midazolam peak plasma concentration (Cmax) by 2.4-fold and systemic exposure (AUC) by 5.4-fold.

MANAGEMENT: Use of idelalisib should generally be avoided with drugs that are primarily metabolized by CYP450 3A4, particularly those with a narrow therapeutic range (e.g., antiarrhythmics, anticonvulsants, antineoplastics, immunosuppressants) or those that are considered sensitive substrates (e.g., ergot derivatives, statins, oral midazolam, triazolam). Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever idelalisib is added to or withdrawn from therapy, if coadministration is required.