Defining patient risks from expanded preventive therapies

In clinical trials, all lipid-lowering agents have been associated with mild, asymptomatic elevations of alanine aminotransferase (ALT) and asparate aminotransferase enzymes. This, along with the fact that 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors are hepatotoxic in some animals, led the US Food and Drug Administration (FDA) to recommend monitoring of liver enzymes for all lipid-lowering agents, except the bile acid sequestrants. Because the drugs act by different mechanisms, ALT elevations may be a pharmacodynamic effect related to lipid lowering, rather than a direct effect of the drug. Animal studies support this assumption. ALT elevations of 3 times the upper limit of normal occur in <3% of patients in clinical trials of lipid-lowering drugs. The elevations are transient and often dose-related, and they usually revert to normal while continuing therapy and have never been associated with hepatotoxicity. Confounding factors include alcohol, acetaminophen, and pre-existing liver disease, such as chronic hepatitis C and type II diabetes with fatty liver, which are both associated with mild, intermittent elevations of ALT. The more important issue is whether or not lipid-lowering agents are hepatotoxic. There are case reports of hepatotoxicity (cholestasis, jaundice, hepatitis, chronic active hepatitis, fatty liver, cirrhosis and acute liver failure) with all of the drugs, except cholestyramine. To date there are just 5 cases of documented liver failure linked to lovastatin. There is no evidence that monitoring reduces the rate of hepatotoxicity. Mild elevations of ALT that occur with many drugs, including HMG-CoA reductase inhibitors, do not predict hepatotoxicity. Liver enzyme elevations appear to be a class characteristic of lipid-lowering agents. Hepatotoxicity is a rare idiosyncratic reaction, occurring only with sustained released nicotinic acid.