Source: Medicines and Medical Devices Safety Authority (NZ) Revision Year: 2017 Publisher: Apotex NZ Ltd., 32 Hillside Road, Glenfield, AUCKLAND 0627 Telephone: (09) 444 2073, Fax: (09) 444 2951, E-mail: NZcustomerservice@apotex.com
Pharmacotherapeutic group: peripheral vasodilators
ATC code: C04AC Includes low strength preparations (e.g. nicotinic acid tablets 50 mg). C10AD Nicotinic acid preparations in high strength (e.g. nicotinic acid tablets 500 mg) is used as a cholesterol reducer.
Nicotinic acid is a water-soluble B complex vitamin which is able to reduce serum lipids. It lowers serum cholesterol and triglyceride concentrations by inhibiting the synthesis of very low density lipoproteins (VLDL) which are the precursors to the formation of low-density lipoproteins, the principal carrier of blood cholesterol.
Several possible modes of action have been proposed, including inhibition of hepatic synthesis of lipoproteins containing apolipoprotein B-100, promotion of lipoprotein lipase activity, and reduction of free fatty acid mobilisation from adipose tissue with an increase in faecal output of sterols. Oral therapy produces reduced triglyceride concentrations within several hours and reduced cholesterol concentrations with several days.
Nicotinic acid also has a vasodilation effect when administered in large doses, identified by flushing of the skin while plasma nicotinic acid levels are rising. This process is believed to be mediated by prostacyclin. Vasodilation occurs within 20 minutes of an oral dose and persists for about 20-60 minutes.
Nicotinic acid has been reported to stimulate histamine release resulting in increased gastric motility and acid production which may activate peptic ulcer. Reports have also indicated that large doses of nicotinic acid may decrease uric acid excretion and impair glucose tolerance. These effects may result in precipitation of an episode of gout in susceptible patients and may necessitate adjustment of diet and anti-hyperglycaemic therapy in diabetic patients.
The normal physiological role of nicotinic acid is as a component of the coenzymes NAD and NADP which are essential for oxidation-reduction reactions in tissue respiration. Nicotinamide, a metabolite of nicotinic acid, possesses similar function as a vitamin but has no pharmacological value in reducing lipids.
Nicotinic acid is readily absorbed from the gastrointestinal tract following oral administration and is widely distributed in the body tissues. It is metabolised in the liver to nicotinamide when taken in physiological doses but when therapeutic doses are taken only a portion is converted to nicotinamide with the remainder eventually being excreted unchanged in the urine. Nicotinamide is widely distributed in the body and is further metabolised in the liver to N-methylnicotinamide and the 2-pyridone and 4-pyridone derivatives with some nicotinuric acid also being formed before being excreted in the urine. The elimination half-life is approximately 45 minutes, and time to peak serum concentration after oral administration is also 45 minutes.
Not applicable.
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