Comparative evaluation of pharmaceutical products obtained in Mexico: Augmenting existing scientific data

Context: The accessibility of pharmacies in neighboring countries has facilitated the trend of acquiring medications outside of local borders. However, scientific data assessing the drug content and quality of these medications has not increased in a corresponding fashion. Objective: This study seeks to augment existing scientific data. Materials and methods: Seventeen products that were obtained from pharmacies in Mexico were evaluated for active ingredient content. The active pharmaceutical ingredients (API) assessed included amoxicillin, ampicillin, ciprofloxacin, levothyroxine, sildenafil citrate, sulfamethoxazole, trimethoprim, and warfarin. API content was analysed with high performance liquid chromatography assays and the resultant data interpreted by applying United States Pharmacopeia (USP) acceptability limits. Results: All of the samples analyzed for the two ciprofloxacin products and the two ampicillin products were found to be within the USP limits. Of the four different sulfamethoxazole/trimethoprim products tested, all were within USP limits for sulfamethoxazole, but contained 23 individual units which were outside of USP limits for trimethoprim. Several of the remaining products (amoxicillin, levothyroxine, sildenafil citrate, and warfarin) had individual units that fell outside of the USP limits, although only one of the levothyroxine products (1 out of 20 tablets tested) and both sildenafil citrate products (all of the units tested) contained units outside of ±25% label claim.