(oxytetracycline hydrochloride)


Terramycin, Liquamycin, Biomycin, Medamycin, Biocyl, Oxyject


  • Tablets: 250 mg
  • Capsules: 250 mg
  • Injectable: 50 mg/mL, 100 mg/mL


Primarily bacteriostatic, oxytetracycline is a Tetracycline derivative which is obtained from Streptomyces rimosus. It shares the same spectrum of activity with Tetracycline against most infections caused by trachoma, rickettsiae, mycoplasma, and chlamydia, as well as Gram-positive and Gram-negative bacteria. However, other semi-synthetic tetracyclines produce longer effects and can be given in lower and less frequent doses than can oxytetracycline.

The drug is widely distributed to organs and tissues including passing through the placenta and into the fetus of pregnant animals, but only a small amount enters the central spinal fluid. It is excreted into breast milk and eliminated unchanged primarily via glomerular filtration and may accumulate with repeated dosing in those with impaired renal function. Oxytetracycline is apparently not metabolized, but excreted into the GI tract where it may become inactive after chelation with fecal material.


Used to treat wound and skin infections as well as mild respiratory infections. Active against mycoplasma. This drug is also used as prophylactic treatment following surgery or injury.

Drug Interactions or Contraindications

  • In renal insufficiency or hepatic impairment, avoid concurrent administration of other nephrotoxic or hepatotoxic drugs.
  • Has a decreased effect when given with antacids or GI products containing aluminum, calcium, zinc, or magnesium, or with iron containing preparations (e.g., multivitamins).
  • Bacteriostatic tetracycline drugs may interfere with the bactericidal effect of the penicillins, cephalosporins, and the aminoglycosides.
  • Oxytetracycline can retard fetal skeletal development in the rat, do not use in the pregnant or nursing doe, unless benefit outweighs risk.

Adverse Reactions

Blood: neutropenia, esinophyllia

CNS: intracranial hypertension

EENT: sore throat

GI: anorexia (loss of appetite)

Skin:  itching

Dosage Recommendations

10 mg/kg to 20 mg/kg, PO, q8hr  1, 2, 26, 27, 34, 41, 42, 44, (Tyzzer’s disease).


6 mg/kg to 10 mg/kg, IM, q12hr 2, 27


0.4 mg/mL in drinking water 1, 26


Terramycin soluble powder= 1/2 to 1 tsp./8oz water/Fresh daily 4
*Note: Terramycin powder is used in the water bottle, be sure to cover the bottle as the drug is light sensitive. Mixture may be kept in the refrigerator for 3 days, changing the water bottles on the cages daily. Place one ounce per rat in the water bottle daily. Prescription/non-prescription available. Although inexpensive, treating in drinking water is not desired. Remove moist foods from diet while treating with medication in the water to encourage drinking. 4


20 mg/kg, IM, q8hr to q12hr  42


60 mg/kg, IM, q3days  26, 34


100 mg/kg, SQ, q24hr 34, 41, 44


  • Absorption of oxytetracycline may be reduced when given with food and dairy products. It is recommended that they be given 2 hours before or after giving drug.Some drugs are known to be better absorbed without food, but unless a rat is in a hospital environment, we realize that this is impossible for the pet rat owner. It is believed to be far more important to get the medication into the rat, even if you have to mix it in a favorite food, than to worry about whether food will hinder the medications absorption rate.
  • May alter gut flora. It is recommended that a probiotic also be given, such as Bene-Bac.
  • Encourage fluids unless giving medication in drinking water, then reduce moist food while treating.
  • Keep tablets in tightly closed light resistant container and store both tablets and injectable at room temperature.
  • Injectables should be given deep IM if oral is not feasible.
  • Doxycycline (Vibramycin) preferred if there is impaired renal function.
  • In treating suspected polymicrobial infections, where a broader coverage may be needed, synergistic or combination drugs may be used. The following drugs may be seen used simultaneously with oxytetracycline: Tylosin. 1
  • Please note that it is imperative to discuss the changing or adding of any medications during your rat’s treatment with your veterinarian to prevent future resistance of microbes to the drugs prescribed.
  • It is also important to note that decomposed tetracyclines (which includes oxytetracycline) may cause potentially fatal nephrotoxicity (Fanconi’s or Fanconi’s-like syndrome); therefore, it is strongly recommended to discard any outdated (expired) or decomposed medications properly.


Links to


The Rat Guide and its affiliates accept no responsibility for misuse or misunderstanding of its information. This guide in whole or part, exists solely for the purpose of recognizing and understanding the care and illnesses in the pet rat. Please seek advice and treatment from a qualified Veterinarian if your rat is ill.

2000 - 2024 by Karen Grant RN. All rights reserved.
All other written and visual materials used by permission of specific authors for the sole use of the Rat Guide. Please visit our Privacy Policy for details.
Brought to you by KuddlyKorner4u
See Logos page for linking to the Rat Guide.
Contact us here: Rat Guide Team
Please note: Rat Guide email is not checked daily. Send e-mail to if you have an urgent medical problem with your pet rat. When possible, it is always best to take your rat to a qualified rat veterinarian.