Influence of cholestyramine on the pharmacokinetics of cerivastatin

The possible influence of the bile acid sequestering agent cholestyramine, a basic comedication in hypercholesterolemic patients, on the pharmacokinetics of the new HMG-CoA reductase inhibitor cerivastatin was investigated. When both drugs were administered concomitantly in the morning under fasting conditions, a decrease in relative bioavailability by 21% could be observed, possibly due to irreversible adsorption of the statin to the resin. In addition, the delay in absorption led to a 41% decrease in cerivastatin mean maximum plasma concentration which also occurred at later time. A second study addressed in detail the question of time interval required between both treatments to minimize the influence of cholestyramine pretreatment on cerivastatin bioavailability: dosing of cerivastatin at dinner (6 p.m.) or bed time (10 p.m.) with cholestyramine pretreatment 1 hour before meal (5 p.m.) in both treatments. The decrease in mean AUC was now approximately 8-16% depending on the time of pretreatment (1-hour-interval: 16%, 5-hour-interval: 8%), and Cmax decreased by approximately 32%, irrespective of the time of pretreatment. Tmax was increased in both treatments, whereas t1/2 was not changed. The presented data support the conclusion that when administered concomitantly, the bioavailability of cerivastatin is moderately reduced by adsorption to cholestyramine. Following, however, the dosing instructions of both cholestyramine (1 hour before meal) and cerivastatin (once-daily in the evening at dinner or at bed time), i.e. administering both drugs several hours (at least 1 hour) apart, the observed effects on rate and extent of absorption of cerivastatin are unlikely to be of clinical relevance.