Fraudulent antibiotic products on the market for aquaculture use.

Antibiotics in aquaculture are used to treat bacterial infections. In order for these products to work effectively fish need to be properly dosed. One of the emerging issues in aquaculture is under-dosing large populations of fish with antibiotics. This happens inadvertently for a number of reasons including the use of fraudulent medications. In this study we evaluated 17 antibiotic products (8 florfenicol and 9 oxytetracycline brands purchased in Asia) by HPLC to determine if the product labels accurately reflected the active pharmaceutical ingredient (API) in the package. We determined authenticity scores for different batches of products at two separate laboratories by comparing the observed API to the label API concentration. We found that 48 % of the antibiotic batches had authenticity scores below 80 % (i.e. observed API in package was at least 20 % less than the label API concentration). Further, there were 9 or the 31 batches of drugs tested had no measureable API. Some products had variation in their authenticity scores between batches making it difficult to rely on a brand. The price of florfenicol products may help identify products with low authenticity scores, but in the case of oxytetracycline, the price of all the products tested was relatively similar. The findings in this study suggest that not all florfenicol and oxytetracycline antibiotic products on the market in Asia have API concentrations indicated on their labels. This could be problematic for medicating fish on aquaculture farms.