Purchasing medicines outside of points of sale regulated by competent authorities increases the likelihood of exposure to substandard or falsified products. Amoxicillin, a widely used essential antibiotic, has been particularly associated with this issue. However, evidence from middle-income countries such as Mexico remains limited. This study evaluated the pharmaceutical quality of 500 mg amoxicillin capsules purchased from an unregulated point of sale in the Mexican market by assessing compliance with official quality tests, including dissolution profiles. An exploratory comparative study was used, considering two fixed factors: point of sale (regulated or unregulated) and brand. Seven groups were evaluated, representing combinations of these factors, except for one brand unavailable in the regulated market. Samples were subjected to pharmacopoeial quality control tests and in vitro dissolution studies. Due to limited sample availability from unregulated sources, some pharmacopoeial sequential procedures could not be fully completed. Dissolution profiles were compared using similarity factor (f2), dissolution efficiency, and mean dissolution time. Medicines from the unregulated point of sale showed greater variability in quality attributes than those from regulated establishments. Some products exhibited deviations in assay, elevated L1 value in dose unit uniformity, and differences in dissolution performance. One sample showed suggestive evidence of an expiration date tampering. Significant differences in dissolution profiles were observed between certain formulations and the reference product. Although full pharmacopoeial procedures were not completed in all cases, the findings indicated variability and potential inconsistencies in quality, highlighting the need to strengthen regulatory oversight and further studies.
Marmolejo-Bernal et al. (Tue,) studied this question.