Tetracycline

Tetracycline is an older antibacterial in the tetracycline class used for selected susceptible infections. Its systemic veterinary role has diminished as other tetracyclines have become more commonly used. A distinct small-animal application is combination treatment with niacinamide for selected immune-mediated skin disorders, where the purpose extends beyond conventional antibacterial activity.

Group

Tetracycline antibacterial

Mechanism of Action

Tetracycline reversibly binds the bacterial 30S ribosomal subunit and prevents aminoacyl-transfer RNA from accessing the acceptor site. This interrupts protein synthesis and generally suppresses bacterial growth. Proposed non-antibacterial effects include modulation of inflammatory-cell and enzyme activity. These actions provide a rationale for dermatologic combination use, although the contribution of each mechanism is incompletely defined.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Bacterial infection	15–20 mg/kg	PO	Every 8 h
Bacterial infection	4.4–11 mg/kg	IV, IM	Every 8 h
Rickettsial infection	22 mg/kg	PO	Every 8 h	Up to 14 days
Urinary bacterial infection	16 mg/kg	PO	Every 8 h	Up to 14 days
Urinary bacterial infection	18 mg/kg	PO	Every 8 h
Bacteremia or brucellosis	22–50 mg/kg	PO	Every 8 h	Up to 28 days
Lyme disease	22 mg/kg	PO	Every 8 h	Up to 14 days
Small intestinal bacterial overgrowth	5–10 mg/kg	PO	Every 8 h	Up to 28 days
Ehrlichiosis	22 mg/kg	PO	Every 8 h	Up to 28 days
Immune-mediated skin disease adjunct	100 mg/animal	PO	Every 8 h	Dogs under 5 kg. With the same niacinamide amount; taper after response, not a standalone antibiotic course.
Immune-mediated skin disease adjunct	250 mg/animal	PO	Every 8 h	Dogs 5-10 kg. With the same niacinamide amount; taper after response, not a standalone antibiotic course.
Immune-mediated skin disease adjunct	500 mg/animal	PO	Every 8 h	Dogs over 10 kg; exact 10-kg boundary differs between reports. With the same niacinamide amount; taper after response, not a standalone antibiotic course.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Bacterial infection	15–20 mg/kg	PO	Every 8 h
Bacterial infection	4.4–11 mg/kg	IV, IM	Every 8 h
Soft tissue infection	20 mg/kg	PO	Every 8 h	Up to 21 days
Hemotropic mycoplasmosis	10–25 mg/kg	PO	Every 8–12 h	Up to 21 days
Bacteremia	7 mg/kg	IV, IM	Every 12 h
Rickettsial disease	16 mg/kg	PO	Every 8 h	Up to 21 days
Susceptible infection	22–33 mg/kg	PO	Every 8 h

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Enteritis or pneumonia	11 mg/kg	PO	Every 12 h	Cattle regimen is for calves; administered in water or as bolus.
Enteritis or pneumonia	22 mg/kg	PO	Every 24 h	Cattle regimen is for calves; administered in water or as bolus.
Susceptible infection	11 mg/kg	PO	Every 12 h	Up to 5 days; Cattle protocol is for calves.

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Enteritis or pneumonia	11 mg/kg	PO	Every 12 h	Cattle regimen is for calves; administered in water or as bolus.
Enteritis or pneumonia	22 mg/kg	PO	Every 24 h	Cattle regimen is for calves; administered in water or as bolus.

Ferrets

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	25 mg/kg	PO	Every 8–12 h

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	50–100 mg/kg	PO	Every 8–12 h

Chinchillas

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	50 mg/kg	PO	Every 8–12 h
Susceptible infection	20 mg/kg	PO	Every 12 h

Guinea pigs

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	20 mg/kg	PO	Every 12 h

Rats

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	20 mg/kg	PO	Every 12 h

Mice

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	20 mg/kg	PO	Every 12 h

Hamsters

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	30 mg/kg	PO	Every 6 h

Gerbils

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	20 mg/kg	PO, IM	Every 24 h

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	11 mg/kg	PO	Every 12 h	Up to 5 days; Cattle protocol is for calves.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	5–7.5 mg/kg	IV	Every 12 h

Indications

Treatment of selected tetracycline-susceptible respiratory, urinary or soft-tissue bacterial infections in veterinary patients.
Historical treatment of selected susceptible rickettsial, ehrlichial or other intracellular bacterial infections.
Combination treatment with niacinamide for selected canine immune-mediated dermatoses, including cutaneous lupus and some pemphigus disorders, with variable disease-specific evidence.

Contraindications

Avoid repeated systemic treatment in growing animals.

Interactions

Calcium, iron, aluminum and magnesium reduce absorption or cause incompatibility.

Adverse effects

GI upset, effects on developing teeth/bone, feline drug fever and possible hepatic injury at high doses.

Toxicity

Excess can cause GI disturbance, renal accumulation and ruminant microflora suppression; rapid IV administration can provoke collapse or arrhythmias.

Preparations

Preparation	Form	Strength	Route
Tetracycline capsule 250 mg	Capsule	250 mg / capsule	PO
Tetracycline capsule 500 mg	Capsule	500 mg / capsule	PO
Tetracycline oral suspension 100 mg/mL	Oral Liquid	100 mg / mL	PO

Monitoring and Administration

Use susceptibility and response to justify treatment; doxycycline or minocycline often have practical advantages. Drinking-water amounts vary with intake.

Protect from light and freezing; alkaline solutions accelerate decomposition.

Pleurodesis uses 20 mg/kg in saline volume 4 mL/kg infused into the pleural space; this is not IV/IM dosing. Bird food/water regimens are adjunctive, lose potency rapidly and depend on intake; a short conversion-to-pellets protocol uses oral suspension 200-250 mg/kg once or twice daily, not adequate long-term psittacosis monotherapy.