Niacin (Vitamin-B3), Niacinamide : Interactions

by MedlinePlus

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Interactions with Drugs

In theory, there may be an increased risk of liver damage if niacin is taken with alcohol or drugs that are toxic to the liver. Niacin-induced flushing may be increased by simultaneous use of alcohol and nicotine.

Based on human study, use of niacin with cholesterol-lowering drugs, such as "statins" (HMG-CoA reductase inhibitors) including lovastatin (Mevacor®) or atorvastatin (Lipitor®), bile acid sequestrants like cholestyramine, probucol, or anti-lipid agents like gemfibrozil may result in further reductions in cholesterol than caused by either agent alone. Use of niacin with HMG-CoA reductase inhibitors or gemfibrozil may increase the risk of serious side effects such as liver or muscle damage. The bile acid sequestrants cholestyramine and colestipol may reduce niacin absorption into the body.

Based on human study, niacin may increase blood sugar levels, and may require dosing adjustments of insulin or prescription diabetes drugs. In research on children, use of niacinamide and insulin together has been shown to lead to a reduction in insulin dosage in patients with type 1 (insulin-dependent) diabetes mellitus. Caution is advised when using medications that may affect blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare provider. Medication adjustments may be necessary.

Antibiotics can lead to decreased amounts of B vitamins in the body. Conversely, based on animal study, pyrazinamide may increase niacin levels. Use of niacin with neomycin may add to the cholesterol-lowering effects of niacin. Based on laboratory study, niacinamide may interact with the antifungal drug griseofulvin (increases its solubility), with possible effects on its activity.

In theory, niacin therapy may increase the risk of bleeding. There are published case reports of patients who developed reversible abnormal blood clotting (coagulopathy) conditions while taking sustained-release niacin. In addition, low blood platelet number (thrombocytopenia) has been observed in studies of niacin therapy. Some examples of drugs that may increase the risk of bleeding if taken with niacin include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve® ).

Based on animal research, use of niacinamide with seizure medications like diazepam (Valium®), carbamazepine (Tegretol®), or sodium valproate (Depakote®) may increase their anti-seizure action. In laboratory study, niacinamide has interacted with diazepam (increases its solubility), with uncertain overall effects. If taken with blood pressure lowering drugs, niacinamide may cause a greater lowering of blood pressure.

Based on human study, niacin may alter thyroid hormones, and require dosing adjustment of thyroid medications. Based on laboratory research, niacinamide may interact with testosterone, estrogen, or progesterone. Use of birth control pills may increase the amount of niacin produced in the body, thus lowering the doses of niacin needed for treatment.

Interactions with Herbs and Dietary Supplements

In theory, use of niacin or niacinamide with herbs or supplements that have potential to cause liver injury may cause greater risk of liver toxicity. Examples include ackee, bee pollen, birch oil, blessed thistle, borage, bush tea, butterbur, chaparral, coltsfoot, comfrey, DHEA, Echinacea purpurea , Echium spp., germander, Heliotropium spp., horse chestnut, Jin-bu-huan (Lycopodium serratum), kava, lobelia, L-tetrahydropalmatine (THP), mate, Paraguay tea, periwinkle, Plantago lanceolata , pride of Madeira, rue, sassafras, scullcap, Senecio spp./groundsel, tansy ragwort, turmeric/curcumin, Tu-san-chi ( Gynura segetum ), uva ursi, valerian, and white chameleon.

Use of aspirin has been shown to reduce the tingling, itching, flushing, and warmth associated with oral niacin administration, an effect which may also result from use of possible salicylate-containing herbs like black cohosh, meadowsweet, poplar, sweet birch, willow bark, and wintergreen. However, levels of salicylates in herbs may vary or be too low to have this desired effect.

Niacin may add to the effects of herbs that may lower blood cholesterol levels, including fish oil, garlic, or guggal. Based on human study, taking such combinations as chromium polynicotinate (niacin-bound chromium) with grape seed proanthocyanidin, or niacin with β-sitosterol and dihydro-β-sitosterol, may result in greater improvements in cholesterol than either agent alone.

Antioxidants may reduce niacin's beneficial effects on cholesterol levels and heart disease, possibly by interfering with niacin's effects on high-density cholesterol (HDL). Recent research suggests that the addition of antioxidants to a combination of niacin plus simvastatin (Zocor®) reduced the benefit of niacin on heart blood vessel plaques, suggesting possible interference by antioxidants. In other research, use of niacin with vitamin A and vitamin E had greater effects on cholesterol levels than niacin alone. Vitamin E in combination with colestipol and niacin has also been associated with greater benefits on heart blood vessel plaques. This remains an area of controversy.

Based on human study, niacin may increase blood sugar levels, and may require dosing adjustments of hypoglycemic agents. In study with children, use of niacinamide and insulin together has been shown to lead to a reduction in insulin dosage in patients with type 1 diabetes mellitus. Caution is advised when using herbs or supplements that may affect blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment. Possible examples of herbs that may lower blood sugar include: Aloe vera , American ginseng, bilberry, bitter melon, burdock,fenugreek, fish oil, gymnema, horse chestnut seed extract (HCSE), marshmallow, milk thistle, Panax ginseng, rosemary, Siberian ginseng, stinging nettle and white horehound. Agents that may raise blood sugar levels include: Arginine, cocoa, and ephedra (when combined with caffeine).

In theory, niacin therapy may increase risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. There are published case reports of patients who developed reversible abnormal blood clotting (coagulopathy) conditions while taking sustained-release niacin. In addition, low blood platelet number (thrombocytopenia) has been observed in studies of niacin therapy. Multiple cases of bleeding have been reported with the use of Ginkgo biloba , and fewer cases with garlic or saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases. Some examples include: alfalfa, American ginseng, angelica, anise, Arnica montana , asafetida, aspen bark, bilberry, birch, black cohosh, bladderwrack, bogbean, boldo, borage seed oil, bromelain, capsicum, cat's claw, celery, chamomile, chaparral, clove, coleus, cordyceps, danshen, devil's claw, dong quai, evening primrose, fenugreek, feverfew, flaxseed/flax powder (not a concern with flaxseed oil), ginger, grapefruit juice, grapeseed, green tea, guggul, gymnestra, horse chestnut, horseradish, licorice root, lovage root, male fern, meadowsweet, nordihydroguairetic acid (NDGA), onion, papain, Panax ginseng, parsley, passionflower, poplar, prickly Ash, propolis, quassia, red clover, reishi, Siberian ginseng, sweet clover, rue, sweet birch, sweet clover, turmeric , vitamin E, white willow, wild carrot, wild lettuce, willow, wintergreen, and yucca.

Based on laboratory study, niacinamide may interact with herbs or supplements with estrogen-like properties, and theoretically may increase the amount of niacin produced in the body (thus lowering the doses of niacin needed for treatment). Examples of herbs with possible estrogen properties include alfalfa, black cohosh, bloodroot, burdock, hops, kudzu, licorice, pomegranate, red clover, soy, thyme, white horehound, and yucca.

Based on human study, niacin may interact with thyroid-active herbs or supplements such as bladderwrack, and alter thyroid hormone blood tests. Preliminary human research reports that zinc sulfate increases the amount of niacin breakdown products in the urine, suggesting a possible interaction between the two agents.

Interactions with Foods

Hot beverages, when taken with niacin, may worsen niacin-induced skin flushing.

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