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teh-Truh-si-kleen - Pronunciation guide

Brand Names

  • Liquamycin LA-200
  • Terramycin Ophthalmic Ointment


Rx symbolTetracycline antibiotics are a group of antibiotics that are effective against bacterial infections. Because they interfere with the normal growth cycle of the invading bacteria and prevent them from reproducing, the immune system of the horse is able to fight off the infection.


Tetracyclines come in several forms. Oxytetracycline is the most commonly used injectable tetracycline for horses and is the drug of choice for the treatment of Potomac Horse Fever and other diseases caused by Ehrlichia organisms. It is used in combination with sulfa antibiotics to treat bacterial respiratory infections such as pneumonia and pleuritis in racehorses and foals. Doxycycline is another tetracycline antibiotic prescribed by veterinarians.

Tetracycline is also available in topical ointments for use in eyes and on the skin.

Injectable oxytetracycline is occasionally given to young foals born with contracted tendons because it rapidly binds calcium, allowing for muscle and tendon relaxation.

Tetracycline antibiotics are used for respiratory disease in older foals.

Dosage and Administration

Prescription medicationOxytetracycline
Method Dosage
(click row for calculator)
Concentration Period Duration
Intravenous injection1 10 mg/kg 100 mg/ml Daily NA


  • 1For intravenous administration, dilution in water for injection or physiological saline is recommended. Doses of up to 2500 mg (50 mL) can be diluted in 250 mL of diluent, and larger doses in 500 mL of diluent.
  • Federal law restricts this drug to use by or on the order of a licensed veterinarian.
  • Extra-label use of drugs in treating animals is allowable only by licensed veterinarians within the context of a valid veterinarian-client-patient relationship, and does not include drug use in treating animals by the layman (except under the supervision of a licensed veterinarian).
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your equine appears to feel better, the entire treatment plan should be completed to prevent relapse.
  • This medication may be available in forms and concentrations not noted in the above table. Always check the label and literature provided with the medication about the form and concentration and DO NOT USE the calculator if the information differs.
  • Calculator is for educational purposes only. Follow your veterinarian's instructions regarding use of this, or any medication.

Side Effects

Tetracycline antibiotics can cause gastrointestinal problems, including diarrhea, which can be difficult to manage or even fatal. Because of this problem, some veterinarians are reluctant to use these drugs.


Oxytetracycline is very irritating to tissue if any of the drug leaks out of the vein during or after intravenous injection.

Oxytetracycline should be diluted and injected very slowly. Some horses can have an allergic or anaphylactic-type reaction to oxytetracycline injection.

Tetracycline antibiotics should be used with care in animals with liver or kidney disease.

Tetracycline should not be used in dehydrated horses.

Tetracycline should be stopped immediately in any horse that develops diarrhea, and the horse should be isolated until feces are cultured for Salmonella, a contagious and potentially life-threatening bacteria that may cause the horse to develop a full-blown clinical disease following antibiotic administration.

Tetracycline antibiotics cross the placenta and are present in the mare's milk. This can retard bone growth in the fetus and discolor teeth.

Tetracycline drugs are not FDA approved for use with horses, but administration by veterinarians is a common and accepted practice. U. S. Federal law restricts these drugs to use by or on the lawful written or oral order of a licensed veterinarian.

Since tetracycline antibiotics are not generally permitted in drug-free competition, it is important to check with the individual regulatory group.


Tetracycline antibiotics can interfere with the action of bactericidal antibiotics such as penicillin.

Antacids, sodium bicarbonate powder, mineral supplements and multivitamins containing bismuth, calcium, zink, magnesium, and iron can reduce the effectiveness of oral tetracycline antibiotics. Doses should be separated by at least two hours.

Tetracycline antibiotics may increase the effect of anticoagulant drugs such as warfarin.


A small overdose usually has little effect, but may result in diarrhea. Prescription and treatment by an experienced veterinarian are essential.


LA-200 OxytetracyclineLA-200 Oxytetracycline


About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.