Oral anticoagulants: Fenofibrate may enhance the oral anticoagulant effect and thus may increase the risk of bleeding. It is recommended that the dose of anticoagulants is reduced by about one third at the start of treatment and then gradually adjusted - if necessary - whilst monitoring coagulation parameters (International Normalized Ratio).
Cyclosporine: Isolated cases of severe albeit reversible, impairment of renal function have been reported during concomitant administration of fibrate-containing medicinal products and cyclosporin. The renal function of these patients must therefore be closely monitored and the treatment with fenofibrate discontinued in the case of significant changes in diagnostic laboratory parameters.
HMG-CoA reductase inhibitors and other fibrates: The risk of serious muscle damage is increased if fenofibrate is used concomitantly with HMG-CoA reductase inhibitors or other fibrates. Such combination therapy should be used with caution, and patients monitored for signs of muscle damage (see Precautions).
Glitazones: Some cases of reversible paradoxical reduction of HDL-cholesterol have been reported during concomitant administration of fenofibrate and glitazones. Therefore, it is recommended to monitor HDL-cholesterol if one of these components is added to the other. Either therapy should be discontinued if HDL cholesterol is too low.
Cytochrome P450 enzymes: In-vitro studies using human liver microsomes indicate that fenofibrate and fenofibric acid are not inhibitors of cytochrome (CYP) P450 isoforms CYP3A4, CYP2D6, CYP2E1 or CYP1A2. They are weak inhibitors of CYP2C19 and CYP2A6, and moderate inhibitors of CYP2C9 at therapeutic concentrations.
Patients coadministered fenofibrate and CYP2C19, CYP2A6 and especially CYP2C9 metabolised drugs with a narrow therapeutic index, should be carefully monitored and, if necessary, dose adjustment of these drugs is recommended.