Clinical response to statins: Mechanism(s) of variable activity and adverse effects

Statins represent a major advance in the treatment of hypercholesterolemia, a significant risk factor for atherosclerosis. There is, however, notable interindividual variation in the cholesterolemic response to statins, and the origin of this variability is poorly understood; pharmacogenetics has attempted to determine the role of genetic factors. Myopathy, further, has been reported in a considerable percentage of patients, but the mechanisms underlying muscle injury have yet to be fully characterized. Most statins are the substrates of several cytochrome P450s (CYP). CYP polymorphisms may be responsible for variations in hypolipidemic activity; inhibitors of CYPs, e.g. of CYP3A4, can significantly raise plasma concentrations of several statins, but consequences in terms of clinical efficacy are not uniform. Pravastatin and rosuvastatin are not susceptible to CYP inhibition but are substrates of the organic anion-transporting polypeptide (OATP) 1B1, encoded by the SLCO1B1 gene. Essentially all statins are, in fact, substrates of membrane transporters: SLCO1B1 polymorphisms can decrease the liver uptake, as well as the therapeutic potential of these agents, and may be linked to their muscular side-effects. A better understanding of the mechanisms of statin handling will help to minimize adverse effects and interactions, as well as to improve their lipid-lowering efficiency.