» Rat Guide     » Health Guide     » Care Guide     » Medication Guide     » Breeding Guide    


Antimicrobial Agents
Back to Antimicrobial Agents


Ery-Tab, Mycin, Robimycin, Robitabs, Eryc, EryPed and EryPed drops.

(Ornacyn sold over counter for birds in pet store. Note: however, that although some birdbiotics and fishbiotics may be used in emergencies by pet rat owners, it is not recommended to do so. Compounding to dose for accuracy may be difficult depending on how they are distributed. For example whether they are sold as powder form, as a capsule or as a tablet. In addition since these products are not federally regulated they may not be of the same quality and purity as those administered by prescription. It is recommended to always seek the advice of a qualified veterinarian regarding treatment of an ill rat.)


Tablets, capsules, granules, suspensions, drops, and injectable.


A macrolide, bacteriostatic antibiotic, erythromycin is believed to inhibit bacterial protein synthesis by binding to the ribosomal 50S subunit. It is used in the treatment against Gram-positive bacilli such as, Bacillus anthracis, corynebacterium, clostridium, and the Gram-positive cocci, staphylococcus and streptococcus, as well as some strains of mycoplasma.
At high concentrations or against highly susceptible organisms erythromycin may act as a bactericidal.

Erythromycin is absorbed in the upper small intestine after given orally. It is widely distributed throughout most body fluids and tissues with the exception of a lesser amount in cerebral spinal fluid. It crosses the placental barrier and appears in breast milk.

Erythromycin is metabolized partially in the liver and excreted in bile along with a small amount in urine.

Some 2 year studies in rats have documented no observable teratogenic or carcinogenic effects at greater than the human dose.
In another study it was shown that at similar doses there may be decreased contractility of the uterus in the pregnant rat. *Note: dosages used in both studies were at greater than the therapeutic range for the rat (see references to studies listed below).
Based on animal studies, erythromycin is considered safe to use during gestation in women.


Can be used in mild respiratory infections

Drug Interactions or Contraindications

Because chloramphenicol and lincosamides are antagonists of erythromycin, they should not be used concurrently.
Use of theophylline with erythromycin may increase toxicity.

Adverse Reactions

GI:  anorexia, diarrhea

Skin:  itching

Other:  pain at injection site

Dosage Recommendations

5 mg/lb to 10 mg/lb, PO, TID  4


if using ornacyn, 1/2 to 1 tablet in 2 oz. water mixed daily  4


1/8 tablet in food TID  4
Give med for at least 14 days


20 mg/kg, PO, q12hrs  34


  • Considered safe, it is still wise to consult with a vet if you think your rat is pregnant or if your rat is nursing.
  • If mixing med in water, reduce moist food to encourage rat to drink.
  • Store capsules and tablets at room temperature.
  • Solutions and suspensions should be refrigerated. However some individual oral suspension products are stable for 14 days at room temperature. Check with veterinarian or pharmacist.
  • Erythromycin - Erythromycin Thiocyante - Erythromycin Stearate: Summary Report 1. (n.d.). Retrieved December 12, 2008, from http://www.emea.europa.eu/pdfs/vet/mrls/Erythromycin%201.pdf.
  • Erythromycin. (1995, July 25). Retrieved December 12, 2008, from http://www.usp.org/pdf/EN/veterinary/erythromycin.pdf.
  • Granovsky-Grisaru, S., Ilan, D., Grisaru, D., Lavie, O., Aboulafia, I., Diamant, Y., & Hanani, M. (1998). Effects of erythromycin on contractility of isolated myometrium from pregnant rats. Am J Obstet Gynecol, 178(1 pt 1), 171-4. Retrieved December 12, 2008, from http://www.ncbi.nlm.nih.gov/pubmed/9465824?dopt=Abstract.

Posted on June 23, 2003, 14:23, Last updated on September 10, 2016, 13:46 | Antimicrobial Agents

Rat Guide Logo
All other written and visual materials used by permission of specific authors for the sole use of the Rat Guide.
Brought to you by KuddlyKorner4u
See Logos page for linking to the Rat Guide.
Rat Guide brought to you by KuddlyKorner4u