Major Uses

Azithromycin is a common antibiotic in the macrolide class used to treat a variety of susceptible bacterial infections in dogs, cats, horses, and other species. The drug acts by interrupting bacteria protein synthesis by binding to the 50S ribosome, a cellular structure that only some bacteria have to produce internal proteins. Some examples of susceptible bacteria that azithromycin might be prescribed to fight include Staphylococcus, Streptococcus, Bordetella spp, and Borrelia burgdorferi (an agent of lime disease). These bacteria may cause dermatological, respiratory tract, and urogenital infections.

Common Precautions

Patients taking azithromycin rarely experience side effects, however, with most medications, adverse reactions can occur. The most common effects reported if the medication is taken at high doses are vomiting, diarrhea, and abdominal pain or cramping. If these reactions persist, the pet's veterinarian should be contacted. It is also recommended that the liver function of the patient be normal before the drug is administered. Liver damage, which may cause jaundice, can be a possibility if the animal is predisposed to liver disease. Some patients may show reactions at the IV site when azithromycin is administered intravenously. It is also recommended to use the drug with caution when it is administered to pregnant or lactating animals; there is not sufficient data of its safety.

Because drug interactions can occur, the pet's veterinarian needs to be informed of all medications, vitamins, and supplements the pet is taking before azithromycin is prescribed. Azithromycin may interact with the following drugs: antacids, cyclosporine, digoxin, cisapride, and pimozide.

Azithromycin should not be administered in animals with a known allergy or hypersensitivity to the drug or other macrolide antibiotics. Signs of an allergic reaction may include swelling of the face, hives or scratching, or seizures. Signs of an overdose may be excessive vomiting or diarrhea. The pet's veterinarian, or emergency veterinarian care, should be sought immediately if these reactions occur.


Azithromycin tablets should be stored in a light resistant, childproof container at room temperature at no higher than 86° F. The oral suspension should not be refrigerated, but also stored at room temperature and given within 10 days of reconstitution (the process of the powder form mixed with water).


The drug is supplied in 250, 500, and 600mg tablets, 500mg vials for injection, and 100mg/5mL, 200mg/5mL, and 1g/packet of powder form to be mixed with water for the oral suspension. The oral suspension should be shaken well before use and given on an empty stomach. The typical dose for a dog is 2.5-5 mg/lb (5-10 mg/kg) by mouth once daily for up to seven days. For cats, the usual dose is 2.5-7.5 mg/lb (5-15 mg/kg) by mouth every 12-24 hours for up to seven days. To treat the Rhodococcus equi infection in horses, the typical dose is 5 mg/lb (10 mg/kg) by mouth once a day. Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

If a dose is missed it should be taken as soon as possible, unless it is almost time for the next dose. If it is almost time for the next dose, the missed dose can be skipped and the regular dosing schedule should be followed; two doses should not be given at once. The prescribing veterinarian should be contacted if there are any questions or concerns.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.