Niacin (Vitamin-B3), Niacinamide : Dosing

by MedlinePlus

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Adults (18 years and older)

Note: Taking niacin with food may reduce stomach upset and the risk of stomach ulcer.Doses are usually started low and gradually increased to minimize the common side effect of skin flushing. Taking aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) at the same time during the first 1 to 2 weeks may reduce this flushing. Use of an antihistamine 15 minutes prior to a niacin dose may also be helpful. The flushing response may decrease on its own after 1 to 2 weeks of therapy. Extended release niacin products may cause less flushing than immediate release (crystalline) formulations, but may have a higher risk of stomach upset or liver irritation. In general, not all niacin products are equivalent. Patients switching from one product to another may have an increase or decrease in side effects.

Dietary intake: The dietary reference intake established by the Food and Nutrition Board for niacin (in the form of niacin equivalents, 1 milligram niacin = 60 milligrams tryptophan) ranges from 16 to 18 milligrams daily for adults, with a maximum intake of 35 milligrams daily.

High cholesterol: Clinical trials have most commonly studied immediate release (crystalline) niacin at doses of 500 to 3000 milligrams taken by mouth daily. Dosing may be started at 100 milligrams three times daily and increased gradually to an average of 1000 milligrams three times daily, as tolerated. Significant increases in high-density lipoproteins (HDL) by up to 30% may occur at doses ranging from 1 to 1.5 grams daily. Mild reductions in low-density lipoprotein (LDL) levels may occur at these doses, with stronger effects (up to 20%) occurring at higher doses (3 to 4.5 grams daily), or when used with a "statin" drug or bile acid sequestrant. The maximum recommended daily dose is 3 grams, although some studies have used 4.5 to 6 grams daily. Extended or sustained release niacin may be started at a dose of 500 milligrams daily (or nightly), and increased to 1 to 2 grams per day.

Pellagra (niacin deficiency): Dosing in the range of 50 milligrams to 1 gram daily has been studied.

Atherosclerosis: Niacin in doses of 1 to 4 grams daily has been studied.

Cardiovascular disease: Niacin at a dose of 3 grams daily has been studied.

Diabetes mellitus (type 1), preservation of β-islet cell function: Niacinamide has been studied in the preservation of pancreas cell (β-islet) function in patients with newly diagnosed diabetes mellitus (type 1) in divided doses, up to 3 grams daily.

Children (younger than 18 years)

There is not enough scientific evidence to recommend the safe use of niacin or niacinamide in children. Niacinamide has been studied in children at daily doses of 150 to 300 milligrams per year of the child's age, or 25 milligrams per kilogram daily, for the prevention of type 1 diabetes mellitus in "high-risk" individuals. No serious side effects have been reported, although safety and effectiveness are not clear. Patients should speak with a qualified health care provider if considering this therapy.

Note that there are concerns about the lack of evidence regarding treatment of childhood lipid disorders, including long-term psychological and metabolic effects. For many disorders, dietary alteration is considered acceptable as first line treatment, without the use of lipid-lowering drugs until adulthood is reached.

Safety

Allergies

Rarely, anaphylactic shock (severe allergic reaction) has been described after intravenous or oral niacin therapy.

Side Effects and Warnings

Most people taking niacin experience skin flushing and a warm sensation, especially of the face, neck and ears, when they begin treatment or increase dose. This reaction is usually mild, but has been intolerable enough to cause up to half of participants in studies to stop therapy. Dry skin and itching is also commonly experienced. Taking aspirin or non-steroidal anti-inflammatory drugs such as ibuprofen (Advil®, Motrin®), naproxen (Naprosyn®), or indomethacin (Indocin®) can reduce the flushing. Use of an antihistamine 15 minutes prior to a niacin dose may also be helpful. Slow-release niacin products may have less skin flushing than regular release niacin preparations or may simply delay the appearance of flushing. The flushing response often decreases on its own after 1 to 2 weeks of therapy. Mild stomach upset, nausea, vomiting and diarrhea also may occur when beginning niacin therapy, and usually resolve with continued use.

More serious side effects include liver toxicity, worsening of stomach ulcers, and altered blood chemistry levels (increased blood sugar and uric acid concentrations). Numerous case reports describe liver toxicity, including increased liver enzyme levels in the blood, skin yellowing (jaundice), fluid in the abdomen (ascites), or liver failure. Monitoring of liver blood tests while using niacin is recommended. While slow-release niacin products may have less skin flushing than regular release niacin preparations, they may worsen stomach and liver side effects.

Niacin can cause significant alterations in blood sugar levels and insulin. This has been a potential concern in patients with diabetes, although a recent randomized controlled trial reports that of 148 patients, only 4 discontinued niacin because of inadequate glucose control (doses of 1000-1500 mg per day in a controlled release formulation were used). Nonetheless, caution is advised in patients with diabetes or hypoglycemia, and in those taking insulin, drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary. Although niacinamide is generally not associated with other side effects, it may affect insulin and blood sugar levels.

In theory, gout may occur during niacin treatment, due to increased blood uric acid levels. Lactic acidosis has been reported after taking sustained-release niacin. Niacin-induced muscle cell damage (myopathy) and increased blood levels of creatine kinase (a marker of muscle damage) have been reported in studies.

Abnormal heart rhythms and heart palpitations have occurred in niacin studies. Based on human research, taking niacin alone or with colestipol may increase blood homocysteine levels. High levels of homocysteine have been associated with an increased risk of heart disease.

Blood clotting problems have been reported during treatment with sustained-release niacin. Caution is advised in patients with bleeding disorders or taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary. Low white blood cell number (leukopenia) and slightly increased blood eosinophils have also been reported.

Rarely reported side effects include headache, tooth or gum pain, dizziness, breathing difficulty, increased anxiety, panic attacks, and decreased thyroid function (hypothyroidism). There are published accounts of temporary side effects of the eye including macular swelling and blurred vision as well as toxic amblyopia ("lazy eye"). These side effects resolved when niacin was stopped.

Pregnancy and Breastfeeding

Use of niacin supplementation during pregnancy or breastfeeding is not recommended due to lack of sufficient research of safety and effectiveness.

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