Purpose: The dissolution profiles of nonprescription extended-release niacin and inositol niacinate products were studied using the prescription extended-release niacin, Niaspan, as a reference.
Methods: Seven nonprescription extended-release and 12 nonprescription inositol niacinate products were collected from community and online pharmacies in the United States. Extended-release Niaspan was used as a reference. Dissolution profiles were examined by the United States Pharmacopoeia dissolution test, using a paddle method. Release samples were removed every 30 minutes for up to 240 minutes. Niacin was quantified by high-performance liquid chromatography.
Results: Ten out of the 12 inositol niacinate products were capsules and 6 of the 7 extended-release formulations were tablets. During the initial 30-minute dissolution study of inositol niacinate products, free niacin was released to various degrees. One product achieved fast dissolution, with >30% cumulative release of niacin. The cumulative percentage of niacin released at 240 minutes of all inositol niacinate products was statistically different (p < 0.0001). The majority of these products reached a plateau of releasing niacin in one to two hours, which was maintained until the end of the study. Six out of the seven extended-release niacin products had extended-release profiles. Five products showed a statistically higher dissolution rate (p < 0.05) than that of Niaspan.
Conclusion: Significant variations in dissolution profiles were noted among the 7 nonprescription extended-release and 12 nonprescription inositol niacinate products in vitro, and their dissolution rates were not comparable to that of the prescription extended-release niacin. Further studies are warranted to correlate such dissolution data with their in vivo efficacy.