By Rania Gollakner, BS, DVM, MPH

What is clarithromycin?

Clarithromycin (brand name: Biaxin®) is a macrolide antibiotic used to treat certain bacterial infections, such as Helicobacter spp and Rhodocuccus equi in foals.

Its use in cats, dogs, ferrets, horses, to treat bacterial infections is ‘off label’ or ‘extra label’. 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 direction may be significantly different from those on the label.

How is clarithromycin given?

Clarithromycin is given by mouth in the form of a tablet or liquid suspension. It may be given with or without food, however, if gastrointestinal problems occur, give future doses with food. Measure liquid forms carefully, and shake well before use.

This medication should take effect within 1 to 2 hours, and while effects may not be visibly obvious, gradual improvements are usually noticeable after a few days.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects seem uncommon, although information is currently limited in domestic animals. Diarrhea, vomiting, and appetite changes are possible. Stomach pain and cramps are also possible. In cats, ear or generalized skin redness may occur. Serious side effects may include collapse, severe sleepiness, bloody diarrhea, or yellowing of the skin, gums, or eyes; if these are seen, contact your veterinary office.

It is unknown if there are rare effects in pets, but in humans, rare effects such as liver problems, decreased platelets (the blood cells involved in blood clotting), and allergic reactions have occurred.

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?

Clarithromycin should not be used in pets that are allergic to it or other macrolide antibiotics. Do not use in small mammals such as rabbits, gerbils, guinea pigs, hamsters, or in adult horses. Clarithromycin should be used cautiously in pregnant pets, as effects are unknown. Use cautiously in lactating pets; although it is likely safe, there is not enough information on this topic. In horses, clarithromycin should be cautiously in those greater than 4 months old or in horses exposed to hot weather; provide shade and close observation in these environments.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with clarithromycin: alfentanil, alprazolam, amlodipine, bromocriptine, buspirone, carbamazepine, chemotherapy agents, cyclosporine, digoxin, diltiazem, disopyramide, drugs that prolong the QTc interval, fluconazole, ketoconazole, lincomycin, methylprednisolone, midazolam, omeprazole, opioids, quinidine, rifabutin, rifampin, sildenafil, tacrolimus, theophylline, or warfarin, zidovudine.

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?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet at home for serious side effects.

How do I store clarithromycin?

The 250mg tablets should be stored at room temperature between 59°F and 86°F (15°C and 30°C) in a tightly closed container and away from light. The 500mg tablets should be stored at room temperature between 68°F and 77°F (20°C and 25°C) in a tightly closed container. Do not refrigerate the liquid suspension: store at room temperature and discard after 14 days.

What should I do in case of 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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