Tylosin — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	PO	10-20 mg/kg	q12h	Duration: 5-7 days for acute infections; 2-4 weeks for IBD Notes: For IBD, lower doses (5-10 mg/kg) may be used. Administer with food to reduce GI upset.
Cat	PO	10-20 mg/kg	q12h	Duration: 5-7 days for acute infections; 2-4 weeks for IBD Notes: Use with caution in cats due to potential GI upset. Monitor for appetite and vomiting.
Horse	PO	10-20 mg/kg	q12h	Duration: 5-10 days Notes: Oral administration may cause colitis; monitor for diarrhea. For Rhodococcus equi, use higher doses (20-25 mg/kg) and combine with rifampin.
Cattle	IM	10-20 mg/kg	q24h	Duration: 3-5 days Notes: Administer deep IM. Do not exceed 10 mL per injection site. Withdrawal times apply.
Cattle	SC	10-20 mg/kg	q24h	Duration: 3-5 days Notes: SC administration may be less irritating than IM. Follow label directions.
Swine	PO	100-200 mg/kg in feed or water	Continuous	Duration: 3-7 days Notes: Medication via drinking water or feed. Ensure adequate intake.
Swine	IM	10-20 mg/kg	q24h	Duration: 3-5 days Notes: Use deep IM in the neck. Withdrawal times apply.
Sheep/Goat	IM	10-20 mg/kg	q24h	Duration: 3-5 days Notes: Extra-label use; observe withdrawal times.
Rabbit	PO	10-15 mg/kg	q12h	Duration: 5-7 days Notes: May cause GI upset; monitor for diarrhea.
Poultry	PO (water)	25-50 mg/kg	Continuous in drinking water	Duration: 3-5 days Notes: Use in accordance with label for CRD. Withdrawal times for eggs and meat apply.

Clinical Indications & Species Uses

General Indications

Treatment of infections caused by susceptible Gram-positive bacteria and mycoplasmas
Treatment of chronic inflammatory conditions of the gastrointestinal tract

Dog (Canine)

Treatment of chronic diarrhea associated with inflammatory bowel disease (IBD)
Treatment of antibiotic-responsive diarrhea
Treatment of respiratory tract infections (e.g., Bordetella bronchiseptica)
Treatment of skin and soft tissue infections (off-label)
Treatment of mycoplasma infections

Cat (Feline)

Treatment of chronic diarrhea associated with IBD
Treatment of respiratory tract infections (e.g., Mycoplasma felis)
Treatment of conjunctivitis (off-label)
Treatment of skin infections (off-label)

Horse (Equine)

Treatment of respiratory infections (e.g., Rhodococcus equi, Mycoplasma)
Treatment of abscesses and wound infections (off-label)
Treatment of colitis (off-label)

Cattle (Bovine)

Treatment of respiratory disease (e.g., Mannheimia haemolytica, Pasteurella multocida)
Treatment of foot rot (interdigital necrobacillosis)
Treatment of metritis
Treatment of mastitis (off-label)
Treatment of mycoplasma infections

Small Ruminants (Sheep / Goat)

Treatment of respiratory infections (e.g., Mycoplasma, Pasteurella)
Treatment of enteritis (off-label)
Treatment of foot rot (off-label)

Rabbit & Small Mammals

Treatment of respiratory infections (e.g., Pasteurella multocida)
Treatment of enteritis (off-label)
Treatment of abscesses (off-label)

Avian & Poultry

Treatment of chronic respiratory disease (CRD) caused by Mycoplasma gallisepticum
Treatment of infectious sinusitis
Treatment of necrotic enteritis (off-label)
Treatment of erysipelas (off-label)

Exotic & Other Species

Treatment of respiratory infections in reptiles (off-label)
Treatment of skin infections in small mammals (off-label)

Pharmacology & Mechanism of Action

Drug Class: Macrolide antibiotic | Pharmacological Group: Antibacterial

Mechanism of Action: Tylosin is a macrolide antibiotic that acts by binding reversibly to the 50S ribosomal subunit of susceptible bacteria, specifically to the 23S rRNA and ribosomal proteins L4 and L22. This binding inhibits protein synthesis by blocking the translocation step of peptide chain elongation, thereby exerting a bacteriostatic effect. At higher concentrations, it may be bactericidal. Tylosin is effective against a range of Gram-positive bacteria, some Gram-negative bacteria (e.g., Pasteurella, Mannheimia), and mycoplasmas. It also has immunomodulatory effects, including inhibition of neutrophil chemotaxis and modulation of cytokine production, which may contribute to its anti-inflammatory properties in certain conditions.

Pharmacodynamics: Tylosin exhibits time-dependent antibacterial activity with a post-antibiotic effect (PAE) of several hours against susceptible organisms. Its efficacy is primarily related to the duration of time that drug concentrations exceed the minimum inhibitory concentration (MIC) for the pathogen. Tylosin is particularly effective against Mycoplasma species, which are often resistant to other antibiotic classes. In veterinary medicine, it is used for its antibacterial and anti-inflammatory properties, especially in the treatment of chronic respiratory diseases and enteric infections. The drug also has prokinetic effects on the gastrointestinal tract, which may be beneficial in conditions like chronic diarrhea in dogs.

⚡ Pharmacokinetics Summary

Absorption: Tylosin is well absorbed after oral administration in monogastric animals, but absorption is variable in ruminants due to ruminal degradation. In dogs and cats, oral bioavailability is approximately 60-70%. In cattle, oral administration results in poor absorption due to rumen metabolism; therefore, parenteral routes are preferred. Intramuscular and subcutaneous injections provide rapid absorption with peak plasma concentrations within 1-2 hours.

Distribution: Tylosin is widely distributed throughout the body, with high concentrations in tissues such as the lungs, liver, kidneys, and mammary gland. It penetrates well into bronchial secretions and milk. It crosses the placenta but is not known to be teratogenic. Protein binding is moderate, approximately 30-40% in most species. The volume of distribution is large, indicating extensive tissue penetration.

Metabolism: Tylosin is metabolized primarily in the liver to various metabolites, including desmycosin, which retains antibacterial activity. The metabolism is species-dependent, with some species producing different metabolite profiles. In ruminants, significant metabolism occurs in the rumen, reducing systemic bioavailability after oral administration.

Excretion: Tylosin and its metabolites are excreted primarily in bile and feces, with a smaller amount excreted in urine. In lactating animals, it is excreted in milk, which is important for withdrawal times. The elimination half-life varies by species: approximately 1-2 hours in dogs and cats, 2-4 hours in cattle, and 1-3 hours in swine.

Half-Life: Dogs: 1-2 hours; Cats: 1-2 hours; Cattle: 2-4 hours; Swine: 1-3 hours; Horses: 1-2 hours

Bioavailability: Oral: 60-70% in dogs and cats; IM: nearly 100% in most species; Oral in ruminants: low (<20%) due to ruminal degradation

Protein Binding: 30-40% in most species

Available Formulations & Strengths

Oral Tablet 50 mg, 100 mg, 200 mg (PO)

Oral Powder 10 g/lb, 100 g/lb (PO (mixed in feed or water))

Injectable Solution 50 mg/mL, 200 mg/mL (IM, SC)

Oral Solution 10 mg/mL, 50 mg/mL (PO)

Premix 10 g/lb, 20 g/lb, 40 g/lb (PO (feed additive))

Contraindications & Clinical Warnings

Contraindications:

Known hypersensitivity to tylosin or other macrolides
Concurrent use with other macrolides or lincosamides (may antagonize)
Use in horses with a history of colitis or diarrhea
Use in rabbits and other hindgut fermenters with caution due to risk of enteritis
Do not use in animals with severe hepatic impairment

Warnings & Clinical Precautions:

Use with caution in animals with renal or hepatic disease
In horses, oral administration may cause severe colitis; monitor for diarrhea and discontinue if it occurs
In cattle, intramuscular injection may cause tissue irritation; administer deep and rotate sites
In poultry, ensure proper withdrawal times to avoid residues in eggs and meat
May cause gastrointestinal upset in dogs and cats; administer with food
Use in lactating dairy cattle is extra-label; milk withdrawal must be observed
Avoid use in animals with a history of allergic reactions to macrolides

Adverse Effects & Reactions

Common:

Gastrointestinal upset (vomiting, diarrhea, anorexia)
Injection site reactions (pain, swelling, inflammation)
Hypersensitivity reactions (rash, pruritus)

Serious / Severe:

Severe colitis in horses (potentially fatal)
Hepatotoxicity (rare)
Ototoxicity (rare)
Anaphylaxis (rare)

Rare:

Blood dyscrasias
Neurotoxicity
Cardiac arrhythmias

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Other macrolides (e.g., erythromycin, clarithromycin)	Additive effects or potential antagonism; avoid concurrent use	Moderate
Lincosamides (e.g., clindamycin, lincomycin)	Antagonism of antibacterial effect; avoid concurrent use	Moderate
Chloramphenicol	Antagonism of antibacterial effect; avoid concurrent use	Moderate
Beta-lactam antibiotics (e.g., penicillins, cephalosporins)	Potential antagonism due to different mechanisms; use with caution	Mild
Digoxin	May increase digoxin absorption and toxicity; monitor digoxin levels	Moderate
Warfarin	May enhance anticoagulant effect; monitor coagulation parameters	Moderate

Overdose & Toxicity Management

Signs of Toxicity:

Gastrointestinal signs (vomiting, diarrhea, anorexia)
Ataxia
Depression
Tremors
Seizures (in severe cases)
Hepatotoxicity (with chronic overdose)

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Induce vomiting if recent ingestion and animal is conscious. Administer activated charcoal to reduce absorption. Provide fluid therapy for dehydration and electrolyte imbalances. Monitor liver enzymes and renal function. In severe cases, consider anticonvulsants for seizures.

Food Animal Withdrawal Times

🥩 Meat: 21 days🥛 Milk: 96 days🥚 Eggs: 0 days

Withdrawal times vary by formulation and country. For cattle, meat withdrawal is typically 21 days and milk withdrawal 96 hours (4 days) for injectable forms. For poultry, meat withdrawal is 1-5 days and egg withdrawal is 0 days if used according to label. Always follow local regulations and product label.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F), with excursions permitted between 15-30°C (59-86°F).

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light and moisture. Keep container tightly closed. Do not freeze injectable solutions. Store oral powders in a dry place.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in cattle, swine, and poultry in the US. Also approved in other countries for various species.

Extra-Label (Off-Label) Use: Extra-label use in food animals requires a valid veterinary-client-patient relationship and must comply with AMDUCA regulations. Extended withdrawal times may be necessary. In the US, tylosin is approved for use in cattle, swine, and poultry. Use in other species is extra-label.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Tylosin is a versatile macrolide antibiotic commonly used in veterinary practice for its efficacy against mycoplasmas and Gram-positive bacteria. It is particularly valuable in treating chronic respiratory and enteric infections. In dogs and cats, it is often used for inflammatory bowel disease due to its immunomodulatory properties. In livestock, it is used for respiratory disease and enteritis. However, its use in horses is limited due to the risk of colitis. Always consider culture and sensitivity testing before use. Monitor for adverse effects, especially gastrointestinal signs. Adhere to withdrawal times in food animals to ensure food safety.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)