The bioavailability of sustained release nicotinic acid formulations

Area of Science:

• Pharmacokinetics
• Drug Metabolism
• Nutritional Science

Background:

• Nicotinic acid (niacin) is essential for human health.
• Understanding its bioavailability is crucial for effective supplementation.
• Formulation differences can significantly impact drug absorption and metabolism.

Purpose of the Study:

• To compare the bioavailability of three different nicotinic acid formulations.
• To assess the pharmacokinetic profiles of nicotinic acid and its metabolite, nicotinuric acid.
• To evaluate the incidence of facial flushing associated with each formulation.

Main Methods:

• A randomized cross-over study involving seven healthy volunteers.
• Administration of single 500 mg doses of nicotinic acid in rapid-release and two slow-release formulations.
• Measurement of nicotinic acid and nicotinuric acid concentrations in serum (up to 8 hours) and urine (up to 24 hours).

Main Results:

• Relative bioavailability of unchanged nicotinic acid was significantly lower for slow-release formulations (1% and 25%) compared to rapid-release.
• Relative AUC (0-8h) for nicotinuric acid was 15% and 58% for slow-release formulations.
• Relative urinary recoveries of nicotinuric acid were 18% and 59% for slow-release formulations.
• Facial flushing was less pronounced with slow-release formulations.

Conclusions:

• The bioavailability of unchanged nicotinic acid is notably low with slow-release formulations.
• Slow-release formulations result in a higher ratio of nicotinuric acid to nicotinic acid in serum and urine.
• Formulation type critically influences nicotinic acid absorption, metabolism, and associated side effects like flushing.