Background: Although niacin often has beneficial effects on the lipoprotein profile, flushing is an untoward effect associated with its use. Aspirin can only reduce the flushing response by 30-40%. Thus, the aim of the present study was to investigate the mechanisms of niacin-induced flushing, with and without aspirin, in normal, healthy individuals.
Methods: Niacin-induced flushing was evaluated in 30 healthy individuals after oral administration of 1000 mg niacin alone or with 325 mg aspirin. Neurological, autonomic nervous system, and skin blood flow measurements (using laser Doppler on the glabrous and hairy skin of each participant) were made at various times after drug administration. In addition, the systemic release of 9α,11β-prostaglandin (PG) F(2) was determined. Flushing symptoms of redness, warmth, tingling, itching, and intensity were recorded using the modified Flushing ASsessment Tool (FAST).
Results: After aspirin, the mean flushing scores for all symptoms decreased significantly; however, 36-53% of participants still had some degree of symptoms, even though aspirin completely blocked 11β-PGF(2) synthesis. Maximum skin blood flow (MaxSkBF) in both the glabrous and hairy forearm increased significantly after niacin, but decreased significantly after aspirin only in hairy skin. Regression analysis showed that, in glabrous skin, both PGF(2) and parasympathetic activity were significant predictors of MaxSkBF after niacin, contributing 26% and 14%, respectively (total R(2) = 40%).
Conclusions: The present study indicates, for the first time, that the parasympathetic nervous system, in addition to PGD(2) , may play an important role in niacin-induced flushing. Changing the sympathetic/parasympathetic balance in favor of parasympathetic activation may be a good therapeutic target to reduce niacin-induced flushing.
© 2012 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and Wiley Publishing Asia Pty Ltd.