SIMVASTATIN - a patient's guide
Trade name: ZOCOR
Simvastatin is a drug used to lower high levels of cholesterol and other fat-like substances in the blood. It acts both by reducing the production of cholesterol and increasing its rate of removal from the body.
It is given by mouth to people who have hypercholesterolaemia - high cholesterol levels in the blood - to help prevent the development of atherosclerosis.
Atherosclerosis is a fatty sludge that can form inside the tubular lining of the blood vessels carrying high pressure blood (the arteries) and can partially block an artery making it difficult for blood to flow and also making it likely that the blood will clot at that point. If this happens to an artery in the brain, a stroke occurs; if it happens to an artery around the heart then a heart attack (myocardial infarction) will occur.
Simvastatin is therefore given long-term to prevent a stroke or a heart attack both for people who have had one before and for those who are judged to have high risk factors for such an event in the future.
It is most important to understand that the body makes its own cholesterol and indeed it needs to do so for essential reasons. However, a diet high in animal fat can boost the blood cholesterol to dangerous levels. In addition, some people inherit a tendency for the blood cholesterol to be high and have an increased risk of stroke or heart attack.
It is also important to understand that when we talk about cholesterol we are really meaning several fats in the blood. The other term used for all the cholesterol types in the blood is "lipids" and the blood cholesterol test is often called a "fasting blood lipid test" and high cholesterol is often called a "lipid disorder". The lipids commonly measured in the blood test are:
The total cholesterol
The sub-fractions of total cholesterol called (1) HDL (high density lipoprotein) also sometimes called "good cholesterol" (2) LDL (low-density lipoprotein) also sometimes called "bad cholesterol" (3) triglycerides - another fatty substance often called " ugly cholesterol" - hence the saying "the good, the bad and the ugly" when interpreting blood lipid reports.
These are usually measured after an overnight fast and only after 2 days without alcohol. This is to give more accurate results. It is important not to do the test too close to a flu or other illness.
There is no point taking simvastatin unless you try hard to reduce animal fat and excess sugar in your daily diet. If you think that you can safely eat the wrong foods because the simvastatin will compensate, then you are fooling yourself because simvastatin can only carry out its prevention job when other risk factors for atherosclerosis are under control.
The risk factors for formation of atherosclerosis include:
- Certain chemicals from cigarette smoke which get into the bloodstream through the lungs
- High blood pressure
- Lack of exercise
- High blood cholesterol
- High animal fat in diet
- Family history for some people
Who should not take simvastatin?
- Those with active liver disease or with unexplained persistent raised liver enzymes in the blood
- Pregnant or breast feeding women
- Those with severe kidney disease
Who should be careful taking simvastatin?
- Those with a past history of liver disease.
- Those with a heavy use of alcohol.
- Those people who have unexplained aching muscles
- Those with kidney problems.
What are the possible side effects?
Minor side effects:
- Tummy upsets such as constipation, flatulence, diarrhoea, abdominal pain, nausea, dyspepsia.
Potentially serious side-effects:
- Muscular disorders - aching/weakness of muscles with rise in muscle enzymes in the blood. This is more likely to happen in those on therapy with fibrates, immunosuppressants or lipid-lowering doses of nicotinic acid, erythromycin or azole antifungals.
- Fever in conjunction with muscle pain, tenderness or weakness, malaise and raised blood levels of muscle enzymes.
Are there potential interactions with other drugs?
If you are on digoxin for heart problems, simvastatin can increase the blood levels of digoxin by up to 20%. Too high a level of blood digoxin can be dangerous so your doctor may need to reduce the dose of digoxin and measure the blood digoxin level.
What is the dosage?
The usual dose range for adults is between 10-40 mg once daily, usually taken with the evening meal. We usually begin at 10 mg once daily, and measure fasting lipid levels within 4 weeks and adjust dosage according to the response.
The maximum daily dose is 40 mg per day. Zocor comes in 10 mgm, and 20 mgm tablet sizes.
It can only be prescribed in New Zealand as a government subsidised medication after your doctor applies to Health Benefits Limited for a special number which has to go on each prescription (otherwise you will need to pay the full cost). Your doctor has to certify that you have achieved certain criteria and the application has to be accompanied by two cholesterol blood tests one of which has to be a fasting level. Health Benefits will decline the application if the blood tests are more than six months old. All this rigmarole is required by the Government because of the relatively high cost of Zocor.