Inositol Hexanicotinate (IHN) is a specific form of the B-vitamin Niacin (Vitamin B3) marketed as a dietary supplement. It acts as a source of niacin, an essential nutrient crucial for cellular metabolism, coenzyme function, and oxidation-reduction reactions. Although IHN itself is not an essential nutrient, its primary function is to deliver niacin to the body in a modified way. Its unique chemical structure makes it a common alternative to standard nicotinic acid supplements.
Chemical Structure and Composition
Inositol Hexanicotinate is an ester compound formed from inositol and nicotinic acid. Inositol is a sugar-like molecule involved in cell signaling. Nicotinic acid is the chemical name for niacin, the B-vitamin component the body utilizes.
The term “hexanicotinate” describes the molecular arrangement: six nicotinic acid molecules are chemically bonded to one central inositol molecule. The inositol core is completely esterified on all six available hydroxyl groups. This structure acts as a delivery system for niacin.
When ingested, the entire compound is absorbed into the bloodstream before it is broken down. The bonds holding the six nicotinic acid units must be broken for the niacin to become biologically active. This molecular arrangement dictates how the supplement is metabolized and why it functions differently from other niacin forms.
The Mechanism of Action
The functional distinction of IHN lies in its unique metabolic process. After absorption, IHN is gradually broken down, or hydrolyzed, by plasma esterases in the bloodstream. This slow hydrolysis sequentially releases free nicotinic acid and inositol over an extended period.
The release rate of active nicotinic acid is significantly slower than with immediate-release niacin supplements. Standard nicotinic acid rapidly spikes blood levels, triggering the release of prostaglandins D2 and E2. These signaling molecules act on small blood vessels, causing rapid dilation of capillaries, particularly in the skin. This effect is the physiological cause of the intense skin flushing, warmth, and itching associated with regular niacin.
Because IHN releases nicotinic acid gradually, the concentration of free niacin never reaches the high threshold required to provoke a major prostaglandin release. Nicotinic acid serum levels peak six to ten hours after IHN ingestion, compared to the half-hour peak seen with free nicotinic acid. This controlled, sustained-release mechanism effectively prevents or significantly reduces the uncomfortable flushing side effect, leading to IHN being called “no-flush niacin.” The released inositol component is metabolized as a sugar alcohol.
Common Therapeutic Applications
IHN is primarily used to support physiological functions benefiting from gradually released niacin. A common application is supporting healthy circulation, as the slow release of nicotinic acid promotes vasodilatation. This widening of blood vessels improves overall blood flow, particularly to the extremities.
This vasodilatory action leads to its use for conditions involving compromised circulation. These include Raynaud’s phenomenon, characterized by reduced blood flow to the fingers and toes, and intermittent claudication, which causes leg cramping due to poor circulation. IHN is sometimes prescribed in Europe for the symptomatic relief of these conditions.
IHN is also used to support healthy cholesterol levels, a known effect of high-dose nicotinic acid. Nicotinic acid helps improve lipid profiles by reducing low-density lipoprotein (LDL) cholesterol and triglycerides while raising high-density lipoprotein (HDL) cholesterol. However, IHN’s effectiveness for significant lipid modification is debated compared to immediate-release niacin. The very slow hydrolysis may prevent the body from achieving the high plasma concentrations needed for the full therapeutic lipid-lowering effect.
Dosage and Safety Profile
Dosage for IHN varies widely depending on the intended application, with clinical trials exploring ranges between 600 mg and 4,000 mg daily. For supporting circulation in peripheral vascular disorders, a common dosage is approximately 3 grams per day, sometimes increased to 4 grams daily. The dose is typically divided and taken throughout the day.
IHN generally presents a favorable safety profile compared to high-dose immediate-release niacin. The primary advantage is the lack of intense flushing, which often hinders compliance with standard niacin therapy. Studies using IHN at doses up to 4,000 mg daily for several months have generally reported no significant adverse effects.
Minor side effects, such as gastrointestinal discomfort, headache, or nausea, are possible but are less frequent and milder than with standard niacin. Individuals should consult a healthcare professional before beginning supplementation. This ensures the supplement is appropriate for their health status and does not interact with existing medications or conditions.