Type: Rx

Description and Use

Metronidazole is an antibacterial, antiprotozoal and anthelmintic for use in multiple species of animals. 

Metronidazole is an antibiotic that is used in horses to treat bacterial infections caused by anaerobic bacteria (bacteria that do not live in the presence of oxygen). While it is very effective against most anaerobic bacteria, metronidazole has no activity against aerobic bacteria (bacteria that require oxygen). Metronidazole is commonly used to treat gastrointestinal diarrhea including clostridial infections. Many of the more serious infections in the horse, such as pleuritis, peritonitis, and abdominal abscesses, tooth infections, and hoof abscesses are caused by a mixture of aerobic and anaerobic bacteria. In these types of cases, metronidazole is given with other antibiotics that have activity against the aerobic bacteria. Metronidazole also is used as an antiprotozoal to treat infections caused by an intestinal protozoal parasite called Giardia.

Side Effects / Adverse Reactions 

 Metronidazole is very bitter-tasting and should be administered orally with a syringe after dissolving the tablets. Metronidazole administration orally may cause your horse to stop eating. Metronidazole is also absorbed rectally. In animals that are unable or unwilling to take this medication orally, your veterinarian may advise the use of this route of administration and will describe the method and provide special tubes for this.

High doses or long-term therapy with metronidazole, such as might be used in a particularly difficult bacterial infection, can cause problems with the central nervous system. Symptoms can include loss of coordination, staggering, disorientation, and even seizures.

Special Precautions

Metronidazole is metabolized by the liver. Animals with liver problems may be more at risk for side effects and are usually given a lower dose of metronidazole.

Metronidazole should not be used in animals that may enter the food chain and it should not be used in animals that are known to be allergic to this drug.


Metronidazole should not be used in pregnant animals, as it has been shown to cause birth defects in laboratory animals.

Drug Interactions

Be sure to review with your veterinarian any medications or supplements your horse may be receiving. Metronidazole may increase clotting time in horses that are receiving an oral blood thinner, such as warfarin. Cimetidine can interfere with the liver’s ability to metabolize metronidazole. In this instance, the metronidazole dose may be reduced.

Available in 250mg or 500mg, 100ct or 500ct