Which antibiotic should never be given intravenously to horses?

Tetracycline is known to have significant adverse effects when administered intravenously to horses. In particular, this antibiotic can cause severe cardiovascular reactions, including arrhythmias and potentially fatal hypotension. This risk is especially pronounced when tetracycline is infused rapidly or at high concentrations. Because of these dangers, veterinarians have established best practices that recommend administering tetracycline via other routes, such as intramuscularly, rather than intravenously to ensure the safety and well-being of the horse.

While other antibiotics listed may have their own specific administration guidelines and potential risks, tetracycline’s clear and well-documented risk profile makes it the one that should never be administered intravenously to horses.