Comparative Dissolution Kinetics of Several Multisource Thioctic Acid Products

Abstract

The relationship between dissolution and bioavailability is an example of the interdependency between the quality of a medicinal product and its safety and efficacy. The uniqueness of thioctic acid is that it can exist in an oxidised and a reduced form, showing lipophilic (lipoic acid) and hydrophilic (dihydrolipoic acid) properties. Bioavailability studies of thioctic acid are necessary to evaluate the expected therapeutic effect and mitigate side effects of the medicinal product.The aim of the study was to carry out equivalence dissolution testing to compare the release of thioctic acid from medicinal products produced by several manufacturers.Materials and methods: the study used a reference medicinal product and three multisource medicinal products by different manufacturers; more specifically, film-coated tablets containing 600 mg of thioctic acid. The experiment was carried out in dissolution media at pH of 6.8±0.05 and 1.2±0.05. Statistical analysis was performed by calculating the average amounts of the substance dissolved, the standard deviation (SD), and the relative standard deviation (RSD, %) using Microsoft Office Excel 2007.Results: The authors chose the testing conditions (dissolution media pH values of 6.8±0.05 and 1.2±0.05) taking into account the nature and characteristics of thioctic acid. The comparison of thioctic acid release profiles based on the calculation of the similarity factor (f2) showed that the dissolution profiles of multisource medicinal products 2 and 3 at pH 6.8 were equivalent to that of the reference medicinal product (more than 85% of the active pharmaceutical ingredient released within 15 minutes) and the dissolution profile of multisource medicinal product 1 was not equivalent to it (with f2 of 28).Conclusions: the established differences in the rate and degree of active ingredient release from the studied medicinal products may indicate possible differences in their pharmacological effectiveness in vivo.

Keywords

• thioctic acid
• comparative dissolution kinetics test
• dissolution test for solid dosage forms
• dissolution medium
• in vitro equivalence