Benefits
Niacin-Form Marketed as Flush-Free
IHN is sold as a niacin supplement that avoids the warm flushing reaction caused by immediate-release nicotinic acid. It does avoid the flush, but the likely reason is that very little niacin is being released: in the trial cited here, IHN showed no evidence of bioavailability and behaved like placebo on every lipid measure. Skipping the flush is not the same as getting niacin's effects.
Studied in People Diagnosed With Raynaud's Disease (One 1988 Trial)
IHN has been sold in Europe under the brand name Hexopal, and one double-blind, placebo-controlled trial from 1988 tested it in people already diagnosed with primary Raynaud's disease, a circulatory condition that makes fingers go cold and white. That single, nearly 40-year-old study in patients is the only trial of this use cited here. It has not been replicated in the evidence on this page, and it does not show what IHN does for circulation in a healthy person.
Not a Reliable Source of Usable Niacin
On paper the molecule is built from inositol plus six niacin units. But the trial cited here found no evidence that the niacin is actually released and absorbed, so IHN should not be counted on as a source of usable niacin. If you want niacin, a plain niacin or niacinamide product is the studied option.
Reported Mild Tolerability
In the 6-week trial of 120 adults, IHN at 1,500 mg a day was well tolerated, with side effects similar to placebo. That is easy to explain: it also performed like placebo on every lipid measure and showed no evidence of being absorbed.
Mechanism of action
Slow Ester Hydrolysis (Proposed)
IHN was designed on the assumption that intestinal and tissue esterases would slowly hydrolyze the ester bonds to release nicotinic acid gradually. In practice, the trial cited here reported no evidence of bioavailability at 1,500 mg a day, so that slow release does not appear to happen to any meaningful degree in people.
Minimal Nicotinic Acid Bioavailability
The blinded 6-week trial in 120 adults with mild to moderate dyslipidemia reported that IHN showed no evidence of bioavailability. That is the simplest explanation for why IHN changed nothing while the extended-release niacin comparison arm lowered LDL by 18 percent in the same study.
Niacinamide Conversion (Proposed, Not Measured)
One proposed explanation is that whatever small amount of niacin is freed gets converted to niacinamide, a form that does not trigger the receptor behind niacin's cholesterol effects. This is a theory put forward to explain the negative result, not something the trials cited here measured.
Clinical trials
Blinded, placebo-controlled trial in 120 adults with mild to moderate dyslipidemia (40 per arm), 1,500 mg a day for 6 weeks after a 4-week diet lead-in (J Clin Lipidol 2013, PMID 23351578)
120 adults with mild to moderate dyslipidemia, 40 each assigned to wax-matrix extended-release niacin, IHN, or placebo
Wax-matrix extended-release niacin lowered total cholesterol by 11 percent, LDL by 18 percent and non-HDL by 15 percent, and raised HDL by 12 percent (all statistically significant). IHN produced no significant improvement in lipids and was no different from placebo, and the authors reported that it showed no evidence of bioavailability. Their own summary was that IHN was well tolerated but was no better than placebo in lipid improvement and showed no evidence of bioavailability. One more thing worth knowing: in the niacin arm, average liver enzymes rose 24 to 27 percent, which is why niacin at lipid-changing doses is a medical therapy that needs monitoring rather than a product to switch to on your own.
Double-blind, randomized, placebo-controlled trial of IHN (sold as Hexopal) in people diagnosed with primary Raynaud's disease (Clin Rheumatol 1988, PMID 3044673)
People diagnosed with primary Raynaud's disease, a circulatory condition, not healthy adults
This 1988 trial reported some symptom improvement with IHN compared with placebo in people already diagnosed with Raynaud's disease. It is a single, small, nearly 40-year-old study with no replication in the evidence cited here, it measured nothing about cholesterol or circulation in healthy people, and a supplement is not a treatment for Raynaud's disease.