Simvastatin is a prescription statin drug introduced in 1991 by Merck under the brand name of Zocor. Simvastatin is classified as a HMG-Co-A reductase inhibitor and was approved by the U.S. Food and Drug Administration to lower cholesterol and triglycerides in the bloodstream, as cited by Drugs.com. Simvastatin 80 mg, the highest dosage available, has the potential to cause the most side effects.
Mode of Action
Like all statin drugs, simvastatin inhibits production of the liver enzyme, HMG-Co-A reductase, which is needed for making cholesterol, as cited on RxList.com. Consequently, less cholesterol and triglycerides are made by the liver and released into the blood, which reduces circulating fats and LDL levels---thought to be the detrimental type of cholesterol. LDL cholesterol is considered a causal factor in atherosclerosis, an artery disease that contributes to the risk of heart attacks and strokes.
Side Effects on Muscle Tissue
According to DailyMed, simvastatin can cause muscle pain, tenderness and weakness, or worse, rhabdomyolysis, which is the destruction of muscle tissue. The risk of simvastatin causing myopathy or rhabdomyolysis is dose-related. From a clinical trial database, it was concluded that 80 mg of simvastatin daily caused the greatest incidence of serious muscle symptoms at more than 25-times more prevalence than the 20 mg dose.
Potential Effects on the Kidneys
DailyMed notes that simvastatin can cause creatine kinase levels in the blood to become ten-times higher than normal, due to the muscle tissue damage. In addition, the process of rhabdomyolysis causes myoglobin protein and other chemical by-products from muscle cell destruction to be released into the bloodstream. Creatine kinase, and especially the myoglobin protein can harm the kidneys by clogging them, which can lead to acute kidney failure.
Side Effects on the Liver
MayoClinic.com claims that the use of statins such as simvastatin can cause increased liver enzymes in some patients, which is a sign of liver impairment and a risk factor for liver damage. Liver enzyme tests should be taken prior to starting statin drug therapy and about six weeks later for comparison.
RxList adds that increases in liver enzyme levels, sometimes three-times beyond normal, have been reported in approximately 1 percent of clinically studied patients on simvastatin. The patients most affected were given 80 mg per day.
Most Common Side Effects
According to the "Compendium of Pharmaceuticals and Specialties," the most common side effects noted from clinical studies of Zocor include upper respiratory tract infections in about 9 percent of patients; headache in about 7 percent of patients; abdominal pain in more than 7 percent of patients; constipation in more than 6 percent of patients; and nausea in more than 5 percent of patients.
Post-marketing Reported Side Effects
DailyMed notes that post-marketing reports of simvastatin side effects included some that were rarely noted in the clinical trials. These user-reported side effects include achy joints, itchy skin, skin rash, skin hives and diarrhea.
References
- Drugs.com: Simvastatin Generic
- RxList.com: Zocor - Simvastatin
- DailyMed: Simvastatin Tablets
- MayoClinic.com: Statin Drug Risks
- "Compendium of Pharmaceuticals and Specialties"; Canadian Pharmacists Association; 2010
