Nonprescription fish antibiotics:: Are they the same as those prescribed to humans?

Patients at a dental school were observed to self-medicate for dental pain and presumed infection with nonprescribed ornamental fish antibiotics, thereby circumventing professional health care. This study determined if the human-approved antibiotics, amoxicillin and cephalexin, were present in the nonprescribed, over-the-counter fish antibiotics.

Human-grade prescribed and over-the-counter commercially-available fish antimicrobials (amoxicillin, cephalexin) were analyzed by using high-performance liquid chromatography ultraviolet-visible detection following US Pharmacopeia (USP) protocols. The contents of 20 capsules of each type were combined and dissolved in a carrier fluid to a concentration of 1 mg/mL. Samples were analyzed using high-performance liquid chromatography at a flow rate of 1.5 mL/min using isocratic mobile phase conditions.

All products contained the equivalent of not less than 90.0% and not more than 120.0% of their labeled contents, within the USP standards. Although no major impurities were identified, there was evidence of several as-yet unidentified excipient ingredients. Results confirm that the human-grade prescribed and nonprescribed over-the-counter fish antibiotics tested match USP standards and are pharmacologically indistinguishable.

The results of this study showed that the major component of the amoxicillin and cephalexin capsules marketed for fish contain their purported levels of antibiotics.