Drug Interactions between boceprevir and Parlodel

GENERALLY AVOID: Coadministration with potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of bromocriptine. Orally administered bromocriptine is extensively metabolized in the gastrointestinal tract and liver by CYP450 3A4, with approximately 93% of the absorbed dose undergoing first-pass metabolism and only the remaining 7% reaching systemic circulation. As such, inhibitors of CYP450 3A4 may markedly reduce the metabolic clearance of bromocriptine. The interaction has been studied with erythromycin, a moderate CYP450 3A4 inhibitor. When a single 5 mg oral dose of bromocriptine was given following a 4-day treatment of erythromycin estolate 250 mg four times a day in five male volunteers, mean bromocriptine peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 4.6- and 3.7-fold, respectively, compared to administration of bromocriptine alone. An even greater magnitude of interaction should be expected with more potent inhibitors. High bromocriptine plasma levels may increase the frequency and/or severity of adverse effects such as nausea, headache, dizziness, somnolence (e.g., episodes of sudden sleep onset), hypotension, syncope, and impulse control problems or compulsive behaviors (e.g., gambling or sexual urges; uncontrolled spending).

MANAGEMENT: Concomitant use of bromocriptine with potent CYP450 3A4 inhibitors should be avoided when possible. In patients who have been treated with a potent CYP450 3A4 inhibitor, an adequate washout of the inhibitor (approximately 3 to 5 elimination half-lives) is recommended prior to initiation of bromocriptine. If coadministration with a potent CYP450 3A4 inhibitor is required, bromocriptine dosage should be reduced to avoid toxicity. Caution and close monitoring for development of adverse effects are advisable, and the bromocriptine dosage further adjusted if necessary.

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