Doctors often prescribe medications containing niacin, one of the eight B vitamins, to help patients control high cholesterol. Although it's effective, niacin can cause several side effects, some temporary and minor and others potentially severe. The high concentrations of niacin in these medications can cause interaction with your blood and organs as well as other medications you are taking.
Identification
Though several common foods -- including chicken, salmon, tuna and fortified cereal -- are good sources of niacin, you'll almost never see side effects from niacin in daily sources alone. Your recommended daily intake is about 30 mg per day for men and 20 mg per day for women. If you're taking a medicinal form of niacin, however, you might be taking doses of between 500 mg and 2,000 mg several times a day, perhaps more than 100 times the amount your body is accustomed to from dietary sources. It's for this reason that you should take niacin medications only under a doctor's supervision.
Flushing
One of the most common side effect is the "niacin flush," a reddening of the skin usually around the face, neck, arms or chest. Less commonly, it can cause skin irritations, such as rashes. Medical researchers are still studying what exactly causes this, although the common theory is that niacin causes your skin cells to produce a compound called prostaglandin, resulting in the reaction. The flushing usually is short-lived, and you can lessen it by taking aspirin before you take niacin, but check with your doctor before following this route. Longer-term rashes or irritation might indicate an allergic reaction to niacin.
Toxicity
Some side effects, including nausea and vomiting, are related to the toxicity of high doses of niacin, according to the Linus Pauling Institute. Over time, high doses of certain forms of niacin can damage your liver cells and function, causing side effects such as jaundice or even hepatitis. Niacin also can boost uric acid levels in your blood, leading to gout. Other side effects related to toxicity include high blood sugar levels, blurred vision and abdominal discomfort. Your doctor will monitor for long-term problems related to these conditions and probably will avoid prescribing niacin in the first place if you have pre-existing conditions such as liver disease.
Interactions
If you're using other medications, your side effects might be a result of niacin interacting with those. Niacin enhances the effects of blood-pressure-lowering medications such as alpha-blockers, so you might experience low blood pressure if you take them both. Similarly, niacin makes the effects of anticoagulants stronger, which could cause bleeding. Niacin's tendency to increase blood sugar also could be amplified if you are taking medication to control diabetes. Make sure your doctor knows every medication, prescription and over-the-counter, that you take before taking niacin.
References
- Mayo Clinic: Niacin (Oral Route)
- "Journal of Clinical Investigation"; Seeing Red: Flushing Out Instigators of Niacin-Associated Skin Toxicity; Richard Dunbar et al.; July 2010
- Oregon State University Linus Pauling Institute: Niacin
- Merck: Niacin
- University of Maryland Medical Center: Vitamin B3 (Niacin)
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