Doxycycline for Horses

PetMD’s medications content was written and reviewed by veterinary professionals to answer your most common questions about how medications function, their side effects, and what species they are prescribed for. This content shouldn’t take the place of advice by your vet.

What Is Doxycycline Used for in Horses?

Doxycycline is a prescription antibiotic used in horses for susceptible bacterial infections such as anaplasmosis, Potomac Horse Fever, Lyme disease, and leptospirosis. Doxycycline is also sometimes prescribed for lower respiratory infections, including bacterial pneumonia in foals.

Doxycycline is FDA-approved for human use in various oral formulations under the generic doxycycline and brand names Vibramycin®, Monodox®, and Mondoxyne™, among many others.

Doxycycline is currently not FDA-approved as a veterinary medication. However, it is readily utilized in the veterinary field, and veterinarians can legally prescribe certain human drugs in animals in certain circumstances. This is called extra-label or off-label use because this use isn’t described on the drug label.

Compounded Doxycycline

In certain circumstances, your vet may recommend a compounded formulation of doxycycline.

Compounded medications are prescribed if there’s a specific reason your horse’s health can’t be managed by an FDA-approved drug, such as if your horse has trouble taking pills in capsule form, the dosage strength is not commercially available, or the horse is allergic to an ingredient in the FDA-approved medication.

Compounded medications are not FDA-approved. They’re created by either a veterinarian or a licensed pharmacist on an individual basis to best suit a patient’s particular needs.

Ultimately, your veterinarian will determine whether this oral medication is right for your horse.

Doxycycline is also available as an injectable formulation, but this form is not used in horses due to severe harmful effects associated with intravenous (directly into the bloodstream) administration, including abnormal heart rhythms (arrhythmias), collapse, and death.

How Doxycycline Works in Horses

Doxycycline is a tetracycline antibiotic that works by preventing susceptible bacteria from making the essential proteins required for growth and survival.

Doxycycline Directions for Horses

• Follow the directions on the drug label or as provided by your veterinarian.

• Doxycycline is best absorbed by horses if given on an empty stomach.

Missed a Dose?

Speak with your veterinarian about what to do if you forget to give a dose of doxycycline.

Generally, they may instruct you to give it when you remember, or if it is almost time for your horse’s next dose, to skip the missed dose and resume your normal dosing schedule.

Do not give extra or double doses.

Possible Side Effects of Doxycycline for Horses

Doxycycline is generally well tolerated in horses. Higher dosages may cause:

• Diarrhea

• Colitis

• Decreased appetite

• Kidney damage

Human Side Effects

Doxycycline is also a prescription medication for humans, frequently with dosages different from those prescribed for your pet by a veterinarian.

Due to possible side effects, humans should never use medicine dispensed for their animals and animals should not be given any medicine dispensed for a human’s use. Always wear gloves while administering doxycycline to your horse.

Women who are pregnant or who may become pregnant should avoid contact with this medication.

If you accidentally ingest an animal medication, call your physician or the national Poison Control Center hotline at 800-222-1222.

When To Call Your Vet

Call your veterinarian if any of the following apply:

• Severe side effects are seen (see above)

• Your horse’s condition worsens or does not improve with treatment

• You see or suspect an overdose

• You have additional questions or concerns about the use of doxycycline

Doxycycline Overdose in Horses Information

There are limited toxicity studies to evaluate overdoses of doxycycline in horses. Signs of an overdose may include:

• Loss of appetite

• Abdominal pain

• Diarrhea

• Fever

If you suspect an overdose, immediately contact your veterinarian or an animal poison control center. Consultation fees often apply.

• Pet Poison Helpline® 855-764-7661

• ASPCA® Animal Poison Control 888-426-4435

How To Store Doxycycline for Horses

• Always confirm storage requirements by reading the prescription label.

• Doxycycline should be stored at controlled temperatures between 68–77 degrees F (20–25 degrees C).

• Keep the container tightly closed to protect its contents from moisture and light.

• Compounded medications should be stored according to the compounding pharmacy’s label.

• Keep out of reach of children and pets.