Erythromycin - Oral

By Rania Gollakner, BS, DVM, MPH

What is erythromycin?

Erythromycin (brand names: Gallimycin®, Ery-Tab®, Ery-Ped®, E.E.S., ERYC®, Emycin®, Erybid®, Erythro®, Erythrocin®, PCE®) is a macrolide antibiotic used to treat certain bacterial infections, most commonly Rhodocuccus equi infections in foals. It also acts as a prokinetic used to increase the movement of the gastrointestinal tract. Today, it is not commonly used in species other than horses.

Its use in horses, cats, dogs, ferrets, and birds to treat infections or gastrointestinal mobility problems 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 directions may be significantly different from those on the label.

How is erythromycin given?

Erythromycin is given by mouth in the form of a capsule, tablet, or liquid. Give this medication on an empty stomach; if vomiting, lack of appetite, or diarrhea occur, give future doses with food. Measure liquid forms of this medication carefully. It can also be given as an injection in the hospital setting. This medication will take effect quickly, in about 1 to 2 hours, but effects may not be visibly obvious for 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 of the oral forms include diarrhea, lack of appetite, and/or vomiting. In foals, decreased appetite, teeth grinding, and diarrhea can occur. Abnormal temperature regulation and overheating can also occur in foals. In adult horses, severe diarrhea can occur.

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?

Erythromycin should not be used in pets that are allergic to it, or in pets with liver disease or dysfunction. It should not be used in rabbits, gerbils, guinea pigs, or hamsters. Erythromycin should be used cautiously in pets with abnormal heart rhythms. Use during pregnancy or lactation is likely safe, although studies in animal species are lacking. In horses, use cautiously in those greater than 4 months old or in horses exposed to hot weather; provide shade and close observation in these environments.

Some breeds of dogs (e.g., Collies, Sheepdogs, and Collie- or Sheepdog-cross breeds) are more sensitive than others to medications. This is typically due to a specific genetic mutation (MDR1) that makes them less able to tolerate high doses of certain medications. Therefore, use erythromycin cautiously in these cases.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with erythromycin: alfentanil, alprazolam, azole antifungals, bromocriptine, buspirone, carbamazepine, chemotherapy agents, chloramphenicol, cisapride, clindamycin, cyclosporine, digoxin, diltiazem, disopyramide, lincomycin, methylprednisolone, midazolam, omeprazole, quinidine, sildenafil, sucralfate, tacrolimus, theophylline, triazolam, verapamil, or warfarin. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Erythromycin may also interact with the liver parameters AST and ALT, and could cause falsely elevated values.

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 for adverse side effects including liver problems when using this medication long-term.

How do I store erythromycin?

Capsules and tablets should be stored at room temperature between 59°F and 86°F (15°C and 30°C) in tight containers and protected from light. Oral liquids should be refrigerated.

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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