No Need to Block B3 Side Effects

Drugs treating Niacin flush in heart patients should be skipped

(RxWiki News) Niacin, also known as vitamin B3, is the only drug that boosts good HDL cholesterol. Patients commonly stop taking it because of facial flushing, also known as the "niacin flush."

Researchers are working to develop a combination drug to treat the flushing, but a new study questions whether blocking the bothersome symptom in patients prone to heart disease would be beneficial.

"Boost your HDL cholesterol by eating healthier."

Dr. Garret FitzGerald, senior author and director of the Institute for Translational Medicine and Therapeutics in the Perelman School of Medicine at the University of Pennsylvania, said that potentially blocking the mechanism that causes the flushing is likely to be undesirable in heart patients, and possibly also patients taking niacin.

Niacin, which increases HDL cholesterol while lowering bad LDL cholesterol, stops fat from breaking down. That fat break-down provides opportunity for LDL cholesterol construction.

Taking niacin releases a fat called prostaglandin (PGD2), which causes the flush. This fat ultimately acts on a muscle cell-surface receptor called DP1. A large clinical trial is ongoing to develop a DP-1 blocking medication.

After reviewing evidence from studies in humans and mice, researchers used mice lacking the DP1 receptor. However, they did not expect to detect cardiovascular hazards because mice do not have platelets.

Investigators were surprised to find that deletion of the receptor made mice more susceptible to hardening of the arteries, blood clots formed within blood vessels, and hypertension in some cases. Researchers suggest the findings reflect DP1 expression in vascular and immune cells in mice, like humans, despite the lack of platelets. Additional studies in humans supported those findings, suggesting that heart patients may not benefit from blockage of the receptor.

Dr. FitzGerald said that if a hazard exists it may be confined to heart patients that take niacin, but not aspirin. This is because aspirin protects the heart by thinning the blood, but a receptor blocking drug may negate this benefit.

The study was published in the April edition of the Journal of Clinical Investigation.

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Review Date: 
April 13, 2012