Benzocaine

Side effects & warnings

SAFETY AND HANDLING (BSAVA Part B p.50, verbatim): The powder should be stored dry and stock solutions should be stored in the dark. ACTION (BSAVA Part B p.50, verbatim): Benzocaine is lipid soluble and is rapidly absorbed across the gills and skin, resulting in anaesthesia by impeding peripheral nerve signal transmission to the CNS. USE (BSAVA Part B p.50, verbatim): Sedation, immobilization, anaesthesia and euthanasia of fish. Ideally, the drug should be used in water from the tank or pond of origin to minimize problems due to changes in water chemistry. The dry powder is poorly soluble in water and must be made into a stock solution with acetone or ethanol (e.g. 100 g/l) for more accurate dosing. Before use, the pH of the anaesthetic solution should be buffered with sodium bicarbonate to the same pH as the water of origin. The anaesthetic solution should be used on the day of preparation and be well aerated during use. Food should be withheld from fish for 12-24 h prior to anaesthesia to reduce the risk of regurgitation. The stage of anaesthesia reached is determined by the concentration used and the duration of exposure, since absorption continues throughout the period of immersion. Potency decreases with higher temperatures. Different species vary in their response and may require different concentrations. It is recommended to use the lower dose rates to test the selected drug concentration and exposure time with a small group before medicating large numbers. Fish may retain some movement during anaesthesia, making it less desirable to use SOURCE: Ramsey I, ed. BSAVA Small Animal Formulary, 10th ed. Part B: Exotic Pets. Gloucester: British Small Animal Veterinary Association; 2023. p.50.