A literature search on pharmacokinetic drug interactions of statins and analysis of how such interactions are reflected in package inserts in Japan

Abstract

Statins (HMG-CoA reductase inhibitors) are one of the most widely prescribed classes of drugs throughout the world, because of their excellent cholesterol-lowering effect and overall safety profile except for rare but fatal rhabdomyolysis arising either directly or indirectly by pharmacokinetic interactions with certain other drugs. As package inserts in pharmaceuticals are the primary source of information for health care providers, we carried out a literature search to examine how crucial information was provided in package inserts of five statins approved in Japan (simvastatin, atorvastatin, fluvastatin, pravastatin and pitavastatin). A MEDLINE search from 1996 to June 2004 was carried out to identify studies on clinical pharmacokinetic drug interactions for the five statins. We mainly collected information on area under plasma concentration (AUC) following co-administration of statins with other drugs. The current package inserts used in Japan were obtained from the website of the Pharmaceutical and Medical Device Agency whereas USA package inserts were obtained from the Food and Drug Administration website. The majority of package inserts listed the drugs that interacted with statins with most describing the risk of rhabdomyolysis because of the possibility of increases in blood concentration. However, quantitative information such as change in AUC was provided in only a few cases. Instructions for dosage adjustment are seldom provided in the Japanese package inserts. USA package inserts list almost identical drug interactions as the Japanese package inserts, although they contain more quantitative data, especially for typical cytochrome P450 (CYP) inhibitors. All pharmacokinetic drug interactions including relevant quantitative data for potential effectors and details on mechanisms of interaction need to be given in package inserts as soon as the information becomes available, to ensure safe and proper use of the drugs concerned. Including such information in the package insert will be an extremely valuable aid for health care providers.