Niacin
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Definition of Niacin
Niacin is a water-soluble vitamin that is part of the B-vitamin family. It is found in nuts, eggs, dairy products, fish and enriched breads.
Description of Niacin
Nicotinic acid, the water-soluble vitamin also known as niacin, has been used for many years as a cholesterol-lowering drug. It is considered a drug of first choice because it is safe and effective and has been shown to reduce the risk of heart attack.Niacin lowers total and LDL cholesterol, as well as triglycerides, and raises HDL-cholesterol as well. Niacin can lower LDL cholesterol levels as much as 30 percent. It is also the least expensive cholesterol-lowering drug.
To produce such lipid lowering, niacin is given in therapeutic doses of one and one half grams (1,500 mg) daily or more; doses of up to six grams have been used in clinical studies. Therapeutic doses usually do not exceed 3 grams daily.
Since niacin can cause severe redness and itching of the skin, therapy is usually begun with small doses and gradually increased. An aspirin given one half hour before the drug helps to reduce flushing. In addition, flushing and itching are lessened if the drug is taken on a full stomach, or if a timed-release preparation is used.
It is also helpful to begin the therapy on a non-working day to avoid any potential embarrassment that may occur from the flushing, which gradually diminishes as the body adjusts to the drug.
Dosage And Side Effects
One of the major disadvantages of niacin is that toxic effects may occur when the drug is given in therapeutic doses. These effects include:
- Mild inflammation of the liver
- High levels of blood sugar or uric acid (which causes gout)
- Flu syndrome
- Blurred vision
- A darkening of the skin
- Gastrointestinal complaints.
These effects are easily reversed when the dosage of the medication is lowered. Careful monitoring and supervision by a physician is therefore essential for patients who take niacin.
Although niacin is available in drug stores without a prescription, no one should ever take this drug in therapeutic doses without medical supervision.
Individuals who have had serious liver disease, gouty arthritis, peptic ulcer, gout or significant abnormalities of heart rhythm should not take niacin.
Sustained Release And Instant Release Niacin
The side effects of itching and flushing are minimized when taking sustained-release niacin, which allows the drug to enter the bloodstream more slowly.
However, a new study comparing two generic versions of niacin, a conventional immediate-release (IR) form and a sustained-release (SR) preparation showed that the lower rates of flushing for the SR preparation may be offset by its effect on liver function.
In the trial, 46 adults with elevated cholesterol levels were randomly assigned to take either IR or SR niacin in dosages that increased from 500 mg per day to 3 grams per day. In addition, they followed a diet that restricted saturated fat and cholesterol.
The good news for the SR niacin users was that their total cholesterol levels were lower than in patients who took the IR preparation. Also, at a dosage of 1,000 mg per day, only 22 percent had flushing, tingling, headache, warmth, or itching with SR niacin, versus 53 percent with the IR medication.
The bad news is that the patients who took the SR niacin were more likely to develop abnormalities of their liver function, which occurred with dosages as low as 1,000 mg per day. These abnormalities caused more than half of the patients taking the SR niacin to withdraw before completing the study. IR niacin did not appear to have any such effects, although other studies have shown that IR niacin can also cause serious liver-function abnormalities.
The results of this study should not lead people to discontinue taking an SR preparation that has been effective and is not causing side effects. There are a wide range of sustained-release preparations, with varying degrees of complications and effectiveness, and patients should not generalize about these agents.
Both SR and IR niacin preparations are available without prescription, and these data provide a reminder that over-the-counter drugs, like all drugs, can have side effects, and that niacin can cause liver abnormalities.
Patients taking niacin - whether IR or SR preparations - should undergo liver function tests. Before starting or stopping either form of niacin, patients should discuss the issue with their physicians.
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