Nicotinic Acid
Nicotinic acid is the most extensively studied agent and has been found to lower cholesterol levels as well as prevent cardiovascular disease. In fact, nicotinic acid affects all aspects of your lipid profile by lowering LDL cholesterol by 15 to 25 percent, lowering triglycerides by 20 to 50 percent, and raising HDL cholesterol by 15 to 30 percent. Despite its ability to greatly lower cholesterol, nicotinic acid is also associated with some undesirable side effects, such as flushing, itching, gastrointestinal upset, and hot flashes. The side effects from nicotinic acid can be so troublesome that many discontinue taking it.Because of these side effects, other forms of nicotinic acid have been manufactured and include extended-release (ER) and sustained-release (SR) preparations. These forms are designed to be released into the blood over an extended amount of time and alleviate side effects. Although these preparations do reduce flushing, some of them can produce a side effect that is even worse - liver failure. The extended-release product Niaspan has not been associated with liver failure, but it is only available through prescription.
Nicotinamide
Nicotinamide is an amide derivative of nicotinic acid. This derivative of nicotinic acid has been used to prevent the flushing experienced from taking the nicotinic acid formulations of niacin. There are very little studies that examine nicotinamides ability to lower cholesterol, and the current studies out there suggest that nicotinamide does not lower cholesterol. This can be confusing because both nicotinic acid and nicotinamide are often labeled the as niacin.Inositol Hexaniacinate
Inositol hexaniacinate is often referred to as flush-free or no-flush niacin. It is a modification of nicotinic acid that was specifically designed to alleviate the side effects associated with niacin use. Although it is advertised to lower cholesterol levels, there are very few studies out there about inositol hexaniacinate that support this. Additionally, these formulations are often more expensive than their nicotinic acid counterparts. So, while you are paying to avoid flushing and hot flashes, you may be missing a big benefit -- lowering your cholesterol and your risk for heart disease.Sources:
Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (PDF), July 2004, The National Institutes of Heath: The National Heart, Lung, and Blood Institute.
Meyers CD, Carr MC, Park S, and Brunzell JD. Varying cost and free nicotinic acid content on over-the-counter niacin preparations for dyslipidemia. Ann Intern Med 2003;139:996-1002.

