(for veterinary information only)
BRAND NAME: ERY-TAB, ERY-PED, ERYC, and others
Erythromycin began its story as an antibiotic of the macrolide class (the same class as tylosin and azithromycin). It is made naturally by the bacterium “Streptomyces fradiae” and acts to inhibit the manufacture of proteins by bacteria. This is accomplished by interfering with the bacterial "50S ribosome" which reads messenger RNA and sequences the appropriate amino acids into the coded protein. Non-bacterial cells employ a "60S ribosome" which is not affected.
Lower doses of erythromycin stop bacteria from reproducing but technically do not kill them. The patient's immune system must be able to finish the job. Antibiotics of this type are called "bacteriostatic" antibiotics. At higher doses, erythromycin can kill bacteria out right which makes it also a "bacteriocidal" antibiotic.
HOW THIS MEDICATION IS USED
Erythromycin is used as a stomach pro-kinetic agent as described. It is also used as an antibiotic against infections as described above. It is also the treatment of choice for intestinal infections caused by Campylobacter bacteria.
The most common side effects are nausea, diarrhea, and appetite loss.
INTERACTIONS WITH OTHER DRUGS
Erythromycin should not be used with other drugs that bind the bacterial 50S ribosome or they will compete with each other and interfere with each other. Such other drugs include: clindamycin, lincomycin, chloramphenicol, azithromycin, tylosin.
Erythromycin is synergized (i.e. works even better) when combined with rifampin or sulfa class antibiotics.
Theophylline, an airway dilator, can reduce clearance of erythromycin from the body thus making toxicity more likely. Other drugs that can increase blood levels of erythromycin include omeprazole (an antacid) and the azole class of antifungal drugs (ketoconazole, itraconazole, and fluconazole.)
Sucralfate, a medicine used for stomach ulcers, can interfere with the absorption of erythromycin. Administration of these medicines should be separated by 2 hours.
When erythromycin and digoxin, a heart medicine, are used concurrently the digoxin blood level will be higher and potentially could be toxic. Other drugs that may also show unexpectedly high blood levels when combined with erythromycin include: bromocriptine (used for female hormone imbalances), buspirone (an anti-anxiety medicine), cyclosporine (an immunomodulator), alprazolam (an anti-panic drug), theophylline (the airway dilator mentioned above), and sildenafil (used for pulmonary hypertension) .
The pro-kinetic effect of erythromycin may be diminished over time as the patient develops tolerance to the drug. This situation can be mitigated and possibly actually avoided by combining erythromycin with metoclopramide, another pro-kinetic drug.
CONCERNS AND CAUTIONS
The oral suspension of erythromycin should be stored in the refrigerator, however, after it is dispensed it can be stored at room temperature for up to 14 days.
**THIS DRUG IS TOXIC TO GUINEA PIGS, HAMSTERS, RABBITS AND GERBILS!
This drug is considered able to cause birth defects and should not be used during pregnancy.
The use of erythromycin will falsely elevate the liver enzymes ALT and AST on a blood test. This is not harmful but the veterinarian should be aware of this reaction.
Bioavailability is poor in cats (meaning cats do not absorb the drug from the GI tract well). Erythromycin can be expected to be effective for intestinal infections (i.e. Campylobacter infection) but for an internal infection another antibiotic may be a better choice.
Page last updated: 9/16/2017