Vioxx - Clinical Pharmacology

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VIOXX (rofecoxib tablets and oral suspension) 9556413

Renal Insufficiency

In a study (N= 6) of patients with end stage renal disease undergoing dialysis, peak rofecoxib plasma levels and AUC declined 18% and 9%, respectively, when dialysis occurred four hours after dosing. When dialysis occurred 48 hours after dosing, the elimination profile of rofecoxib was unchanged. While renal insufficiency does not influence the pharmacokinetics of rofecoxib, use of VIOXX in advanced renal disease is not recommended. (See WARNINGS, Advanced Renal Disease.)

Drug Interactions (Also see PRECAUTIONS, Drug Interactions.)

General

In human studies the potential for rofecoxib to inhibit or induce CYP 3A4 activity was investigated in studies using the intravenous erythromycin breath test and the oral midazolam test. No significant difference in erythromycin demethylation was observed with rofecoxib (75 mg daily) compared to placebo, indicating no induction of hepatic CYP 3A4. A 30% reduction of the AUC of midazolam was observed with rofecoxib (25 mg daily).

This reduction is most likely due to increased first pass metabolism through induction of intestinal CYP 3A4 by rofecoxib. In vitro studies in rat hepatocytes also suggest that rofecoxib might be a mild inducer for CYP 3A4. Drug interaction studies with the recommended doses of rofecoxib have identified potentially significant interactions with rifampin, theophylline, and warfarin. Patients receiving these agents with VIOXX should be appropriately monitored.

Drug interaction studies do not support the potential for clinically important interactions between antacids or cimetidine with rofecoxib. Similar to experience with other nonsteroidal anti-inflammatory drugs (NSAIDs), studies with rofecoxib suggest the potential for interaction with ACE inhibitors. The effects of rofecoxib on the pharmacokinetics and/ or pharmacodynamics of ketoconazole, prednisone/ prednisolone, oral contraceptives, and digoxin have been studied in vivo and clinically important interactions have not been found.