• The combination of a fibrate and a statin should be used with caution because of the increased risk of serious muscular adverse effects (myopathy and rhabdomyolysis) [MHRA, 2007]:
• Do not prescribe gemfibrozil with a statin, as the risk of muscular adverse effects is higher than with other fibrates.
• One meta-analysis found that the incidence of rhabdomyolysis increased 10-fold when statins (other than cerivastatin) were combined with gemfibrozil [Law and Rudnicka, 2006].
• Interaction between fibrates and oral anticoagulants [Baxter, 2008]:
• There have been reports of increased bleeding and increased prothrombin times in people taking a fibrate and an oral anticoagulant.
• Apart from clofibrate (which is no longer available in the UK), the clinical significance of this interaction for other fibrates is uncertain as information is generally limited to case reports.
• Overall, the evidence suggests that it would be prudent to monitor the international normalized ratio in people taking a fibrate and an oral coagulant.
• Interaction with ciclosporin:
• Severe cases of reversible renal impairment have been reported during concomitant administration of ciclosporin and certain fibrates (e.g. bezafibrate and fenofibrate). The manufacturer of these fibrates advises close monitoring of renal function when these drugs are used together and to stop the fibrate if there is severe alteration in laboratory values.
• For gemfibrozil:
• Gemfibrozil potently inhibits several cytochrome P450 enzymes (CYP2C8 [an enzyme important for the metabolism of, for example, repaglinide, rosiglitazone, and paclitaxel], CYP2C9 [an enzyme involved in the metabolism of, for example, warfarin and glimepiride], CYP2C19, CYP1A2) and other hepatic enzymes (UGTA1 and UGTA3):
• Do not prescribe gemfibrozil with repaglinide.
• The manufacturer of gemfibrozil advises caution when combining gemfibrozil with rosiglitazone, as increased rosiglitazone levels have been reported (2.3-fold increase).
• Because of the number of enzymes inhibited by gemfibrozil, the manufacturer warns that the interaction profile of gemfibrozil can be complex and can result in an increased plasma level of many medicinal products if administered concomitantly with gemfibrozil.
• With hypoglycaemic agents (oral drugs and insulin): hypoglycaemic reactions have been reported with gemfibrozil and these drugs. The manufacturer advises monitoring glucose levels.

[ABPI Medicines Compendium, 2006b; ABPI Medicines Compendium, 2007b; ABPI Medicines Compendium, 2007d; ABPI Medicines Compendium, 2007e; ABPI Medicines Compendium, 2008b]