DRUG INTERACTIONS
Potential for Drugs to Affect Alvimopan Pharmacokinetics
Based on in vitro data, alvimopan is not a substrate of CYP enzymes. Therefore, concomitant administration of ENTEREG with inducers or inhibitors of CYP enzymes is unlikely to alter the metabolism of alvimopan. No clinical studies have been performed to assess the effect of concomitant administration of inducers or inhibitors of cytochrome P450 enzymes on alvimopan pharmacokinetics.
In vitro studies suggest that alvimopan and its "metabolite" are substrates for p-glycoprotein. A population PK analysis did not reveal any evidence that alvimopan or "metabolite" pharmacokinetics were influenced by concomitant medications that are mild-to-moderate p-glycoprotein inhibitors. No clinical studies of concomitant administration of alvimopan and strong inhibitors of p-glycoprotein (e.g., verapamil, cyclosporine, amiodarone, itraconazole, quinine, spirinolactone, quinidine, diltiazem, bepridil) have been conducted.
A population PK analysis suggests that the pharmacokinetics of alvimopan were not affected by concomitant administration of acid blockers or antibiotics. However, plasma concentrations of the "metabolite" were lower in patients receiving acid blockers or preoperative oral antibiotics (49% and 81%, respectively). Because the "metabolite" is not required for efficacy, no dosage adjustments are necessary in these patients.
Potential for Alvimopan to Affect the Pharmacokinetics of Other Drugs
Alvimopan and its "metabolite" are not inhibitors of CYP 1A2, 2C9, 2C19, 3A4, 2D6, and 2E1 in vitro at concentrations far in excess of those observed clinically. Alvimopan and its "metabolite" are not inducers of CYP 1A2, 2B6, 2C9, 2C19 and 3A4. In vitro studies also suggest that alvimopan and its "metabolite" are not inhibitors of p-glycoprotein. These in vitro findings suggest that ENTEREG is unlikely to alter the pharmacokinetics of coadministered drugs through inhibition or induction of CYP enzymes or inhibition of p-glycoprotein.
Coadministration of alvimopan does not appear to alter the pharmacokinetics of morphine and its metabolite, morphine-6-glucuronide, to a clinically significant degree when morphine is administered intravenously. Dosage adjustment for intravenously administered morphine is not necessary when it is coadministered with alvimopan.
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