What is niacin, and how does it work (mechanism of action)?

Niacin (nicotinic acid, vitamin B3) is a part of the normal diet that is essential to various chemical reactions in the body. It is used medically to treat individuals with deficiency of niacin. Advanced deficiency of niacin can lead to a condition called pellagra in which individuals develop diarrhea, dermatitis (inflammation of the skin), and dementia. Niacin also is used to reduce cholesterol and triglyceride levels in the blood. Specifically it reduces bad cholesterol (LDL cholesterol) and increases good cholesterol (HDL cholesterol). It is not clear how niacin causes its effects on cholesterol and triglyceride levels, but it may be by reducing the production of proteins that transport cholesterol and triglycerides in the blood.

Niacin is available in immediate and slow-release forms (Niaspan, Slo-Niacin). Natural sources of niacin include meat, poultry, liver, fish, nuts, green vegetables, whole grains, and potatoes. Niaspan was approved by the FDA in July 1997.

What brand names are available for niacin?

Niacor, Niaspan, Slo-Niacin, Nicolar (discontinued)

Is niacin available as a generic drug?

GENERIC AVAILABLE: Yes

Do I need a prescription for niacin?

Most formulations are available over the counter.

What are the side effects of niacin?

The most common side effects of niacin are:

• stomach upset,
• flushing,
• headache,
• reduced blood pressure upon standing (orthostatic hypotension),
• vomiting,
• diarrhea,
• itching and
• tingling sensations of the extremities.

Flushing may be reduced by taking 325 mg of aspirin 30 minutes before the niacin and by increasing the dose of niacin slowly. Drinking hot liquids or alcohol shortly before or after niacin is taken may increase the occurrence of flushing. Extended release formulations of niacin may cause flushing less frequently than immediate release formulations.

Rare cases of liver failure or muscle injury have occurred from the use of niacin. Blood tests to monitor for liver injury should be performed before niacin therapy begins, every 6-12 weeks for the first year, and then occasionally thereafter. Niacin should be discontinued if liver tests are greater than three times the upper limit of normal, are persistently elevated, or are accompanied by nausea, vomiting, or weakness.

What is the dosage for niacin?

The recommended oral dose of immediate release niacin for treating high cholesterol levels in adults is 1-2 g two to three times daily. The maximum recommended dose is 6 g daily. When using extended release tablets, the maximum recommended dose is 2 g per day. Niacin should be started at low doses and increased slowly over several weeks. To avoid stomach upset, niacin should be taken with meals.

Extended release tablets should be swallowed whole and should not be crushed or chewed. Extended release formulations should not be substituted with equivalent doses of immediate release niacin since this leads to an overdose of niacin that may cause liver failure.

Pellagra may be treated with up to 500 mg per day of oral niacin.

Which drugs or supplements interact with niacin?

Use of niacin with drugs that cause liver or muscle injury, for example, lovastatin (Mevacor) or simvastatin (Zocor) may increase the occurrence of liver or muscle injury.

Niacin may increase blood glucose levels in individuals with diabetes. Therefore, medications for controlling blood glucose may need to be adjusted when niacin is taken by those with diabetes.

Bile acid sequestrants (for example, cholestyramine [Questran]) bind and prevent absorption of niacin. Administration of bile acid sequestrants and niacin should be separated by 4-6 hours.

Is niacin safe to take if I'm pregnant or breastfeeding?

It is not known whether the high doses of niacin used in treating elevated cholesterol levels are harmful to the fetus during pregnancy.

Niacin is actively secreted in breast milk. Therefore, nursing mothers taking niacin should avoid breastfeeding or discontinue niacin in order to prevent the newborn from ingesting large amounts of niacin.

What else should I know about niacin?

What preparations of niacin are available?

Tablets: 250, 500, 750, and 1000 mg. Capsules: 250 and 500 mg

How should I keep niacin stored?

Niacin should be stored at room temperature from 15 C to 30 C (59 F to 86 F).