Concomitant administration with immunosuppressive drugs, gemfibrozil, niacin (nicotinic acid) and erythromycin is not recommended.
Coumarin Derivatives: When lovastatin and coumarin anticoagulants are administered concomitantly, prothrombin time may be increased in some patients.
In patients taking anticoagulants, prothrombin time should be determined prior to starting therapy with lovastatin and thereafter, monitored at the intervals usually recommended for patients on coumarin anticoagulants.