In vitro data indicate that PRANDIN is metabolized by cytochrome P450 enzymes 2C8 and 3A4. Consequently, repaglinide metabolism may be altered by drugs which influence these cytochrome P450 enzyme systems via induction and inhibition. Caution should therefore be used in patients who are on PRANDIN and taking inhibitors and/or inducers of CYP2C8 and CYP3A4. The effect may be very significant if both enzymes are inhibited at the same time resulting in a substantial increase in repaglinide plasma concentrations. Drugs that are known to inhibit CYP3A4 include antifungal agents like ketoconazole, itraconazole, and antibacterial agents like erythromycin. Drugs that are known to inhibit CYP2C8 include agents like trimethoprim, gemfibrozil and montelukast. Drugs that induce the CYP3A4 and/or 2C8 enzyme systems include rifampin, barbiturates, and carbamezapine. See CLINICAL PHARMACOLOGY section, Drug-Drug Interactions.

Repaglinide appears to be a substrate for active hepatic uptake transporter (organic anion transporting protein OATP1B1). Drugs that inhibit OATP1B1 (e.g. cyclosporine) may likewise have the potential to increase plasma concentrations of repaglinide. See CLINICAL PHARMACOLOGY section, Drug-Drug Interactions.

In vivo data from a study that evaluated the co-administration of a cytochrome P450 enzyme 3A4 inhibitor, clarithromycin, with PRANDIN resulted in a clinically significant increase in repaglinide plasma levels. In addition, an increase in repaglinide plasma levels was observed in studies that evaluated the co-administration of PRANDIN with trimethoprim and PRANDIN with deferasirox, both cytochrome P-450 enzyme 2C8 inhibitors. These increases in repaglinide plasma levels may necessitate a PRANDIN dose adjustment. See CLINICAL PHARMACOLOGY section, Drug-Drug Interactions.

Gemfibrozil significantly increased PRANDIN exposure. Therefore, patients should not take PRANDIN with gemfibrozil. See CLINICAL PHARMACOLOGY section, Drug-Drug Interactions, and CONTRAINDICATIONS.

The hypoglycemic action of oral blood glucose-lowering agents may be potentiated by certain drugs including nonsteroidal anti-inflammatory agents and other drugs that are highly protein bound, salicylates, sulfonamides, cyclosporine, chloramphenicol, coumarins, probenecid, monoamine oxidase inhibitors, and beta adrenergic blocking agents. When such drugs are administered to a patient receiving oral blood glucose-lowering agents, the patient should be observed closely for hypoglycemia. When such drugs are withdrawn from a patient receiving oral blood glucose-lowering agents, the patient should be observed closely for loss of glycemic control.

Certain drugs tend to produce hyperglycemia and may lead to loss of glycemic control. These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid. When these drugs are administered to a patient receiving oral blood glucose-lowering agents, the patient should be observed for loss of glycemic control. When these drugs are withdrawn from a patient receiving oral blood glucose-lowering agents, the patient should be observed closely for hypoglycemia.