there is a caution about the use of niacin and impacts on the liver. however, the problem appears to be with the 'slow release form' which i *assume* means niacinamide.
http://www.ajconline.org/article/S0002- ... 3/abstract
Safety Considerations with Niacin Therapy
Although serious hepatic toxicity from niacin administration has been reported, it is largely confined to the use of slow-release formulations given as unregulated nutritional supplements.