HMG-Co-A reductase inhibitors (“statins”) are metabolized in various ways. Simvastatin and lovastatin are extensively metabolized by CYP3A4 in the intestinal wall and liver. Inhibitors of CYP3A4 can produce marked increases in their effect. Atorvastatin is not metabolized as extensively by CYP3A4, but CYP3A4 inhibitors can still increase its levels substantially. Cerivastatin is metabolized by CYP3A4 and CYP2C8. There is not much information on cerivastatin drug interactions, except that it seems to have a high incidence of muscle damage when it is combined with gemfibrozil. In the US, the combination of cerivastatin and gemfibrozil is contraindicated in the official prescribing information. Fluvastatin is metabolized by CYP2C9, and can have drug interactions involving that enzyme. But pravastatin is not metabolized by the CYP450 system, and of all the statins it appears to be the least likely to have adverse drug interactions.