Interactions with Drugs
Niacin may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples 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®).
Niacin may increase blood sugar levels. Caution is advised when using medications that may alter blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
Niacin may cause low blood pressure. Caution is advised in people taking drugs that lower blood pressure.
Niacin may interfere with the way the body processes certain drugs using the liver's "cytochrome P450" enzyme system. As a result, the levels of these drugs may be altered in the blood, and may cause altered effects or potentially serious adverse reactions. People using any medications should check the package insert, and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
Niacin may also interact with agents for the heart, agents that widen blood vessels, agents used for the liver, agents used for seizures, alcohol, androgens, antibiotics, antigout agents, antihistamines, antithyroid agents, aspirin, benzodiazepines, birth control taken by mouth, calcium-channel blockers, cholesterol-lowering agents (bile acid sequestrants, fibrates, HMG-CoA reductase inhibitors), epinephrine, estrogens, ganglionic blocking drugs, griseofulvin, neomycin, nicotine, nonsteroidal anti-inflammatory drugs (NSAIDs), primidone, probucol, procetofene, progestins, pyrazinamide, theophylline, and thyroid hormones.
Interactions with Herbs and Dietary Supplements
Niacin may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
Niacin may increase blood sugar levels. Caution is advised when using herbs or supplements that may alter blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.
Niacin may cause low blood pressure. Caution is advised in people taking herbs or supplements that lower blood pressure.
Niacin may interfere with the way the body processes certain herbs or supplements using the liver's "cytochrome P450" enzyme system. As a result, the levels of other herbs or supplements may be altered in the blood. It may also alter the effects that other herbs or supplements possibly have on the P450 system.
Niacin may also interact with amino acids, androgens, antibacterials, antigout herbs and supplements, antihistamines, antioxidants, antithyroid herbs and supplements, cholesterol-lowering herbs and supplements, chromium, coffee, ganglionic blocking herbs and supplements, grape seed, herbs and supplements for the heart, herbs and supplements that widen blood vessels, herbs and supplements used for the liver, herbs and supplements used for birth control, herbs and supplements used for seizures, inositol hexanicotinate, kava, minerals, pantothenic acid, phytoestrogens, phytoprogestins, salicylate-containing herbs, sitosterols, sorghum, thyroid hormones, tryptophan, vitamins E, A, and B6, and zinc sulfate.
This evidence-based monograph was prepared by The Natural Standard Research Collaboration