As of 2011, the prevalence of statin use has climbed considerably. From 1988 to 1994, only 2 percent of Americans were prescribed statins. That number increased to 25 percent of Americans from 2005 to 2008. With the rate of use on the rise, concern over the potential adverse effects of statins has grown as well, one of the most common being elevated liver enzymes.
Pharmacology
Statins are a type of medication used to lower high cholesterol, a waxy substance produced by your liver. Excessive production of cholesterol is associated with the build-up of plaque in your arteries--a condition known as atherosclerosis. When this occurs, blood flow to the heart is reduced and may subsequently lead to a heart attack. Statins work by inhibiting an enzyme responsible for producing the precursor to cholesterol known as HMG-CoA.
Effect of Statins on Liver Enzymes
One of the most common adverse effects associated with statin use is elevated liver enzymes. Liver enzymes are proteins released by your liver in response to injury and are used as a detector of liver damage. Studies on statins first emerged in the 1980s, when it was discovered that statins raised liver enzyme levels. Since this time, multiple studies have been conducted on this subject, most of which have demonstrated no such effect. Transient elevations have been shown in some studies; however, these levels were found to return to baseline over time.
Studies
Statins are not only safe for individuals with elevated liver enzymes, but may actually lower liver enzymes and the risk of heart disease in individuals with non-alcoholic fatty liver disease, according to a study published in the December 2010 issue of "The Lancet." The study followed 1,600 participants taking either atorvastatin or a placebo. Among those with mild to moderate liver enzyme elevation at baseline, the statin actually decreased liver enzyme levels, whereas levels increased to greater than three times the normal limit in the placebo cohort. Additionally, 89 percent of participants taking the statin saw liver enzyme levels return to baseline within three years. The statin also lowered the risk of cardiovascular events by 68 percent in participants with elevated liver enzymes at baseline.
Prevalence
Liver enzyme levels are denoted as significant when they surpass three times the upper acceptable limit. When this is taken into consideration, approximately 110 in 100,000 or 0.1 percent of individuals taking statins have significantly elevated liver enzymes on greater than two readings, according to a review of statins by the National Lipid Association. Most elevations are actually transient and it is reported that 70 percent of individuals with levels greater than three times the upper limit will return to normal spontaneously.
Expert Insight
Based on the findings of current literature, the National Lipid Association, NLA, notes that there is "no evidence to support the continued monitoring of liver function tests in patients receiving statin therapy." Furthermore, the NLA no longer recommends regular testing of liver enzymes in individuals with normal baseline lab values who are not at risk for liver failure. Levels should be measured before initiating treatment, 12 weeks after beginning treatment, after increases in dosages and then intermittently.
Warning
Notify your physician immediately if you experience signs or symptoms of hepatotoxicity including yellow discoloration of the skin, enlarged liver, fatigue or malaise. The NLA notes that isolated cases of liver enzyme levels greater than three times the upper acceptable level do not necessitate discontinuance of the medication. Persistently high levels should be investigated to determine the etiology for elevation.
References
- "Health, United States, 2010"; United States Department of Health and Human Services; 2010
- "Journal of Cell Molecular Medicine"; Statins: Mechanism of Action and Effects; Camelia Stancu and Anca Sima; December 2001
- "Heartbeat"; The Statin Hepatotoxicity Myth; Dr. Mario Maiese; December 2010
- "The Lancet"; Safety and Efficacy of Long-Term Statin Treatment for Cardiovascular Events in Patients with Coronary Heart Disease and Abnormal Liver Tests in the Green Atorvastatin and Coronary Heart Disease Evaluation (GREACE) Study: A Post-Hoc Analysis; Vasilios G. Athyros, et al.; December 2010
- "American Journal of Cardiology"; Final Conclusions and Recommendations of the National Lipid Association Statin Safety Assessment Task Force; James M. McKenney, et al.; April 2006
