Tylosin

BRAND NAMES

Tylan®: A well-known brand, particularly for treating gastrointestinal issues in dogs and cats. 

Tysin-50: An injectable brand available in various sizes. 

Tylo-20: Another injectable brand name. 

Tylodot: Used for respiratory infections. 

TyloTon: Used in drinking water for livestock and poultry. 

Tylochem: Available as a powder for solution. 

Other brand names: Other names include Tylorest Vet, Tam-Vet, Tylosef, and Tylosin Tartrate products with specific company-based names.

MECHANISM OF ACTION

Tylosin is a macrolide antibiotic that exerts its antibacterial effect by inhibiting protein synthesis in susceptible bacteria. It specifically binds to the 50S subunit of the bacterial ribosome, near the peptidyl transferase center, which blocks the translocation step during protein elongation. This binding prevents the addition of new amino acids to the growing peptide chain, thereby halting bacterial protein synthesis. As a result, tylosin has primarily a bacteriostatic effect (it inhibits bacterial growth rather than directly killing the bacteria), although it can be bactericidal at higher concentrations or against highly susceptible organisms. Tylosin is particularly effective against Gram-positive bacteria, Mycoplasma species, and certain Gram-negative organisms. Its selective action on bacterial ribosomes, without affecting mammalian cells, accounts for its relatively low toxicity in animals.

PHARMACOKINETICS

Absorption

The absorption of tylosin varies considerably depending on the animal species and the route of administration, such as oral or intramuscular (IM). Additionally, the drug formulation influences the absorption rate, with tylosin tartrate being absorbed more rapidly than tylosin base.

Distribution

Tylosin exhibits a high volume of distribution (Vd), reflecting its extensive dispersion throughout body tissues and fluids rather than confinement to the bloodstream. The exact Vd value can vary based on factors such as animal species, route of administration, dosage form, and physiological conditions, influencing how effectively the drug reaches its target sites within the body.

Metabolism

Tylosin undergoes rapid aerobic degradation in animal excreta, with reported half-lives of approximately 6 to 8 days in species such as cattle, chickens, and swine. During this process, tylosin is not degraded into 14C-volatile compounds or 14CO2, indicating its chemical stability under these conditions. In its producing microorganism, Streptomyces fradiae, tylosin biosynthesis is regulated by intracellular adenylate levels, and factors such as glucose or phosphate supplementation can significantly influence the rate of tylosin production by affecting the organism’s metabolic activity and regulatory pathways.

Excretion

Tylosin is mainly excreted through bile and feces, with smaller amounts eliminated in urine. The rate and route of excretion vary by species and administration method, and only a small portion of the drug is excreted unchanged.

PHARMACODYNAMICS

Tylosin is a macrolide antibiotic with a bacteriostatic effect that disrupts bacterial protein synthesis. While generally bacteriostatic, studies have shown it can be bactericidal at higher concentrations. Its pharmacodynamics (PD) vary depending on the target bacteria and concentration achieved at the infection site. 

ADMINISTRATION

Tylosin can be administered by oral, intramuscular (IM), or intravenous (IV) routes, depending on the animal species and purpose of treatment. It is commonly given orally in feed or water for disease prevention and growth promotion, and IM injections are used for therapeutic treatment of infections, particularly respiratory and mycoplasmal diseases. The choice of route affects the drug’s absorption and effectiveness.

DOSAGE AND STRENGTH

Tylosin dosage and strength vary depending on the animal species, route of administration, and type of infection being treated. Common formulations include tylosin tartrate (for oral use) and tylosin base or tylosin phosphate (for injectable or feed use). Typical dosages are:

• Cattle and swine (IM): 5–10 mg/kg body weight daily for 3–5 days.

• Poultry (oral in feed or water): 0.5–1 g per liter of drinking water or 0.5–1 g per kg of feed.

• Dogs and cats (less common): 10–20 mg/kg orally once or twice daily.

Commercial products are usually available as 100 mg/mL injectable solutions, 100 g/kg premixes, or soluble powders for oral administration. Always follow veterinary guidance and manufacturer recommendations for correct dosage and withdrawal times.

FOOD INTERACTIONS

Tylosin’s absorption and effectiveness can be influenced by the animal’s diet. Foods high in calcium, magnesium, or other divalent cations can bind tylosin and reduce its bioavailability, while fatty meals may slightly alter the absorption rate without significantly affecting overall efficacy. Certain feed additives, such as copper or iron supplements, can also interact with the drug and potentially decrease its antibacterial activity. Administering tylosin on an empty stomach can improve absorption in some species, although in livestock it is often given in feed or water to ensure consistent intake. Therefore, diet and formulation considerations are important to achieve optimal therapeutic outcomes.

DRUG INTERACTIONS

Tylosin can interact with other drugs, potentially affecting its efficacy. Concurrent use with chloramphenicol, lincosamides, or tetracyclines may reduce its antibacterial activity, while combining it with other macrolides is generally unnecessary and may increase side effects. Oral absorption can be decreased by high levels of calcium, magnesium, or iron in feed or supplements. Additionally, tylosin may enhance the effects of neuromuscular blocking agents, so careful use and veterinary guidance are important when administering it with other medications.

CONTRAINDICATIONS

Tylosin is contraindicated in animals with known hypersensitivity to macrolides and should never be used in horses due to the risk of fatal colitis. It should be used cautiously in animals with severe liver disease and avoided in combination with antagonistic antibiotics like chloramphenicol or lincosamides to prevent reduced efficacy.

 SIDE EFFECTS

Tylosin is generally well tolerated, but some animals may experience adverse effects, including:

• Gastrointestinal disturbances: Diarrhea, vomiting, anorexia, or soft stools, especially with oral administration.

• Allergic reactions: Rare hypersensitivity reactions such as hives, swelling, or anaphylaxis.

• Local reactions: Pain, swelling, or irritation at the injection site when given intramuscularly.

• Altered gut flora: Prolonged use can disrupt normal intestinal microbiota, sometimes leading to secondary infections.

OVERDOSE

• Vomiting.

• Drooling.

• Diarrhea, which may be severe or bloody.

• Decreased or loss of appetite.

• Lethargy, weakness, or apathy.

• Lack of coordination.

• Changes to breathing and heart rates. 

TOXICITY

Tylosin has a low toxicity in most animals when used at recommended doses, but overdose can cause severe gastrointestinal upset, liver enzyme elevations, and rare allergic reactions. Horses are particularly sensitive, as even standard doses can lead to fatal colitis, highlighting the need for careful species-specific dosing.