A patient was evaluated by the author for his failure to respond to niacin therapy for abnormal blood lipids. He was to have taken extended-release (ER) niacin to elevate his high-density lipoprotein (HDL) cholesterol of 28 mg/dL. The HDL cholesterol did not change on niacin (500 mg/d for 2 weeks and, then, 1000 mg/d.)
Though the patient took the niacin, it was eventually discovered that he took “flush-free niacin” by mistake. When he switched to ER niacin, the HDL cholesterol increased to 35 mg/dL by taking 1000 mg per day.
“Flush-free niacin” was developed to avoid the flushing that often results from niacin treatment. Flush-free niacin is inositol hexanicotinate which does not contain free niacin. It can be metabolized to form niacin. But, blood levels of niacin are not much improved by taking flush-free niacin. (This explains the absence of flushing.) Flush-free niacin is not classified as a medication and does not come under the control of the United States Food and Drug Administration (FDA.)
Sustained-release (SR) niacin can be metabolized to chemicals which are damaging to the liver (hepatotoxic.) SR niacin has only a minor effect on the HDL cholesterol.
CONCLUSION: Flush-free niacin can’t be used in place of extended-release and intermediate-release niacin. Flush-free niacin does not cause flushing and has no beneficial effect on serum lipids. Niacin has been shown to have the effect of increasing HDL-cholesterol. Sustained-release niacin is hepatotoxic.