Niacin, also known as vitamin B-3, occurs in several different forms that have different names, just to confuse the issue. Niacin, also known as nicotinic acid, niacinamide, also called nicotinamide and inositol hexanicotinate, also called hexaniacinate are the different forms of vitamin B-3. Inositol, an over-the-counter supplement, is often touted by manufacturers as safer and having fewer side effects, such as flushing, than nicotinic acid. Although it was thought at one time that inositol hexanicotinate did not have the same effects on the liver as niacin, this has not been proved to be true, according to NYU Langone Medical Center.
Dosing
Taking any type of niacin, including inositol hexanicotinate, in doses higher than 500 mg per day, but usually at 3 g per day or higher, can cause liver inflammation, which usually reverses when you stop the supplement, NYU Langone Medical Center reports. Extended-release forms of niacin may increase the risk of liver toxicity, MayoClinic.com warns.
Release
Compared to nicotinic acid, inositol hexanicotinate metabolizes more slowly, taking between six to 10 hours to reach maximum serum levels, compared to peaks of 30 minutes to one hour after nicotinic acid administration, according to the European Food Safety Authority. The slow release of inositol hexanicotinate compared to nicotinic acid may explain why the flushing effect does not normally occur with this form of niacin, but that does not mean it won't cause liver damage.
Symptoms
Signs of potential liver damage or liver failure with this supplement include jaundice, a yellowish tinge to the skin and whites of the eyes; darker than normal urine, pale stools or abnormal liver function tests. Fluid accumulation in the abdomen called ascites can also occur. Report signs of liver inflammation to your doctor immediately and stop taking the supplement if they occur.
Considerations
If you're taking any form of high-dose niacin, including over-the-counter inositol hexanicotinate, in doses of 100 mg or more, you may need to have your liver function tests checked through blood tests every three months, the University of Maryland Medical Center suggests. Tell your doctor if you're taking this supplement and do not take it in high doses without medical supervision. If you have existing liver disease or other disorders, do not take it at all without your doctor's approval.
