Major Uses

Erythromycin is a macrolide antibiotic that is effective against a narrow range of bacteria in cats and dogs. It is primarily used to treat respiratory, skin, bone, wound, and sinus infections. It may also be used to treat certain tick-borne infections, such as Lyme disease. Erythromycin is not effective against E. coli or other intestinal-origin coliform bacteria.

Erythromycin works by suppressing protein synthesis and growth to inhibit multiplication of bacteria. At lower doses, this drug stops the reproduction of bacteria so that the immune system is able to eliminate the infection. At higher doses, erythromycin kills bacteria outright.

Common Precautions

Erythromycin is known to cause side effects in some animals. Vomiting is the most common side effect associated with use; dogs are most often affected. Nausea, decreased appetite, and diarrhea are other possible side effects.

Erythromycin should not be used in pregnant animals. It has the potential to cause birth defects. Using erythromycin will falsely elevate ALT and AST, two liver enzymes, on blood tests. Although this reaction is not harmful, it is important to note.

This medication is toxic to rabbits, hamsters, gerbils, and guinea pigs. It should not ever be administered to these animals. It is also not safe for use in adult horses or cattle. Erythromycin may interact with digoxin, theophylline, methylprednisolone, and certain antibiotic drugs.

Erythromycin should not be used in animals with a known allergy or hypersensitivity to the drug. Any known or suspected overdose should be reported to a veterinarian right away.


Erythromycin oral suspension should be stored in the refrigerator. After dispensing, it can be stored at room temperature for up to 14 days. This drug should be stored in its original packaging, out of the reach of children and pets, and away from temperature extremes.


Erythromycin is available as tablets, as capsules, and as an oral liquid suspension.

The typical dose of erythromycin is 5 to 10 mg per pound (10 to 20 mg/kg) every 8 to 12 hours by mouth. The entire treatment course should be completed, even if improvement is noted before the plan is complete. This is important to prevent relapse and resistance. 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 of erythromycin is missed, it should be taken as soon as possible. If it is almost time for the next dose, the missed dose should be skipped and a normal dosing schedule should be resumed. It is important not to take two doses of this medication at the same time.

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.