By Rania Gollakner, BS, DVM, MPH

Close up view of a tick on a dog's muzzleWhat is azithromycin?

Azithromycin (brand name Zithromax® or Zmax®) is a broad-spectrum antibiotic used for a variety of bacterial, rickettsial, and parasitic infections. It is often combined with other drugs to treat specific infections, such as atovaquone to treat babesiosis in dogs. Azithromycin may also have anti-inflammatory, immune-modulating, and gastrointestinal motility effects.

In cats, it is used off-label to treat upper respiratory infections, bartonellosis, cryptosporidiosis, toxoplasmosis, or in combination with atovaquone to treat cytauxzoonosis. In dogs, it is used off-label to treat cryptosporidiosis, or in combination with atovaquone to treat babesia. It is also used for certain infections in horses, cattle, rabbits, guinea pigs, and birds.

Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully, as their directions may be significantly different from those on the label.

How do I give azithromycin to my pet?

Azithromycin is given by mouth in the form of a tablet or liquid suspension. It also comes in an injectable form that can be given intravenously by your veterinarian. Tablets are preferably given with food. The liquid form should be shaken before dosing and preferably given on an empty stomach. Measure the liquid form carefully.

This medication should take effect within one to two hours; however, effects may not be noted outwardly.

What if I miss giving my pet a dose of the medication?

Give the missed dose as soon as you remember, and then wait the recommended amount of time between doses. Never give your pet two doses at once or give extra doses.

Are there any potential side effects from azithromycin?

Azithromycin can cause vomiting, decreased appetite, and diarrhea. If gastrointestinal side effects occur in rabbits, rodents, or horses, stop this medication and contact your veterinarian.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Azithromycin should not be used in animals sensitive to macrolide antibiotics. Use cautiously in animals with liver disease or certain abnormal heart rhythms. It should be used cautiously in animals with a history of vomiting. Use cautiously in pregnant or nursing animals, as safety studies are limited for these situations.

Are there any drug interactions I should be aware of?

Drug interactions with azithromycin have not been reported in animals. There are many classes of drugs that may interact with azithromycin as seen in human studies. Your veterinarian will weigh the potential risks when combining medications and use additional monitoring as needed. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Monitor for side effects and to ensure the medication is working.

How do I store azithromycin?

Tablets should be stored in a tightly sealed container, protected from light, at room temperature (less than 30°C or 86°F). Oral suspension (liquid form) should be stored at room temperature for up to 10 days, then discarded.

What should I do in case of an emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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