The control of intestinal parasites in your dog is essential to the good health of the animal and its family. A veterinarian should treat the dog as soon as signs appear because some of these organisms are zoonotic (transmissible to humans). One of the more common veterinary medications for intestinal disease in dogs is metronidazole.
Metronidazole is an antibiotic used to treat dogs with several types of intestinal disease. Veterinarians usually prescribe metronidazole to dogs presenting in the clinic with diarrhoea that can be attributed to either a protozoal or bacterial infection of the intestinal system. Metronidazole destroys the protozoa Giardia by eliminating the shedding of its cysts so that it cannot reproduce in the animal's body. It has also been shown to kill clostridium, an anaerobic bacterium, and is an effective treatment against amoebiasis. Veterinarians may also recommend using metronidazole to treat inflammatory bowel disease and degenerative liver disease because of its ability to kill the overabundance of intestinal flora that occurs in dogs with these conditions.
Metronidazole works by destroying the DNA of anaerobic bacteria (organisms that reproduce without needing oxygen) and enteric protozoa. This causes the intracellular metabolism of these parasites to fail so they can no longer ingest nutrients and/or reproduce.
Available in 250- and 500-mg tablets, metronidazole can also be prescribed in a liquid suspension form for home use. It can be used as an injection in a veterinary setting. Vets usually recommend dosing dogs with 15 mg of metronidazole per kilo weight (0.998kg.) of the animal twice a day. This means that an 18.1-kg (40-pound) dog will get 272 mg of medicine every 12 hours. If the veterinarian recommends dosing the same size dog three times a day, the dosage is usually 218 mg each time.
While major side effects are not commonly associated with the use of metronidazole, dogs given the drug will sometimes show physical signs of its unusually sour, metallic taste. They may salivate and drool, gag and regurgitate and might be seen pawing at the mouth. Veterinarians normally recommend that owners mask the taste of the drug with peanut butter, cheese or some other palatable treat to get the animal to swallow the dose. Less common side effects might include dark-coloured urine due to pigment changes, lethargy and depression and an unwillingness to eat.
Accidental overdosing and moderate to long term high-dose therapy of metronidazole may result in toxicity with neurological symptoms in the animal. These signs might include staggering and disorientation with limb stiffness. The dog may have muscle tremors that proceed to seizures and involuntary eye movements. A veterinarian should be seen immediately if the dog shows any major or minor side effects of this medication.
Metronidazole is not recommended for use in pregnant dogs as it has been shown to cause birth defects in lab animals. Because it is excreted from the body by the kidneys and liver, metronidazole is not normally given to dogs with these compromised organs because too much of the drug might stay in the animal's system. It is also not recommended for dogs on anticoagulants (blood thinners) or anti-seizure medication as it can interfere with the action of those medications.