Tilmicosin for Cow: Uses, Dosing & Side Effects

This information is for educational purposes only. Never give your pet any medication without your veterinarian's guidance. Dosing, frequency, and safety depend on your pet's specific health profile.

Tilmicosin is a prescription macrolide antibiotic used in cattle, most commonly as the injectable product Micotil 300. It is labeled for subcutaneous use only in cattle and is used under your vet's direction for certain respiratory infections. In the United States, it is primarily associated with bovine respiratory disease, often called BRD or shipping fever.

This drug is known for concentrating well in lung tissue and in immune cells within the respiratory tract. That is one reason your vet may consider it when pneumonia or high-risk respiratory outbreaks are a concern in a herd. It is not a routine medication for every cough or fever, and it should only be used when the diagnosis, handling setup, and food-animal withdrawal planning all make sense.

Tilmicosin also carries an unusually serious human safety warning. Accidental self-injection can be fatal, and the FDA warns that even small accidental exposures can cause severe heart effects in people. Because of that, handling, restraint, and administration method matter as much as the drug choice itself. Your vet may recommend a different option if safe administration cannot be assured.

In cattle, tilmicosin is labeled for the treatment of bovine respiratory disease (BRD) associated with susceptible bacteria including Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni. It is also labeled for the control of respiratory disease in cattle at high risk of developing BRD, which means your vet may use it in selected outbreak or arrival situations where disease pressure is high.

That does not mean it is the right fit for every respiratory case. Your vet will weigh the animal's age, production class, severity of illness, likely bacteria involved, prior antibiotic exposure, and whether the animal is intended for meat or milk production. Tilmicosin is not approved for female dairy cattle 20 months of age or older, because use in that class can lead to milk residue concerns.

In practice, your vet may discuss tilmicosin as one option among several long-acting BRD antibiotics. The best choice depends on the herd situation, resistance concerns, handling safety, and withdrawal needs. A cow with severe depression, labored breathing, dehydration, or poor response to prior treatment may need a broader workup and a different treatment plan.

Tilmicosin dosing in cattle should be determined by your vet and matched to the exact product label. For Micotil 300, the labeled cattle dose is commonly 10 mg/kg (4.5 mg/lb) given once by subcutaneous injection, which equals 1.5 mL per 100 lb body weight. Merck also lists a broader reference range of 10 to 20 mg/kg SC once for beef cattle and dairy cattle under 20 months, but labeled product directions should guide real-world use.

This medication should be given subcutaneously only. It should not be given intravenously, and intramuscular use can cause local tissue damage. Accurate body weight matters, because underdosing may reduce effectiveness and overdosing increases risk. Your vet may also advise where to inject, how much volume to place per site, and what restraint setup is safest for both the animal and the handler.

Food-animal restrictions are a major part of dosing decisions. In U.S. labeling, tilmicosin products for cattle are associated with a meat withdrawal period, and they are not for use in female dairy cattle 20 months of age or older. Withdrawal details can vary by product and jurisdiction, so your vet should confirm the exact interval that applies to your animal, operation, and label in use before treatment starts.

Many cattle tolerate tilmicosin reasonably well when it is used correctly, but side effects can happen. Reported reactions in cattle include injection-site swelling or inflammation, lameness, decreased feed or water intake, collapse, anaphylaxis-like reactions, and in rare cases death. Because macrolides can irritate tissues, some local soreness or swelling may be seen after injection.

Tilmicosin is also known for cardiac toxicity, especially if it is given by the wrong route or at excessive doses. Merck notes that tilmicosin can cause tachycardia and decreased heart contractility, and cattle have died after intravenous injection. If a treated cow seems weak, collapses, shows worsening breathing effort, or declines suddenly after treatment, contact your vet right away.

There is also a separate and very important safety issue for people. See your vet immediately if there has been any accidental human exposure while treating a cow, and seek emergency medical care for the exposed person at once. FDA states there is no antidote and that accidental human injection can cause severe heart effects and death.

Tilmicosin is a macrolide antibiotic, so your vet will be cautious about combining it with other drugs that may affect the heart or that overlap in antibacterial action. Merck advises that macrolides generally should not be used with chloramphenicol or lincosamides because these drugs may compete for the same bacterial ribosome binding site, which could reduce effectiveness.

Extra caution is also reasonable when other medications with cardiovascular effects are being used. Tilmicosin itself has recognized cardiotoxic potential, so your vet may avoid pairing it with drugs that can worsen heart rhythm or contractility concerns. This is especially important in stressed, dehydrated, or severely ill cattle.

Because tilmicosin is used in food animals, interaction decisions are not only about safety. They also affect residue avoidance, treatment records, and antimicrobial stewardship. Tell your vet about any recent antibiotics, anti-inflammatories, supplements, or herd-level metaphylaxis protocols before a dose is given.