Benefits

• Metronidazole effectively fights anaerobic infections, infections growing without the presence of oxygen. Anaerobic bacterias cause infections that occur at surgery sites, in the mouth, the gastrointestinal tract, deep wounds or tissues, the vagina and internal organs. As an antibiotic, it fights against certain gastrointestinal parasites, especially Giardia.
  
  Metronidazole is also used successfully as an anti-inflammatory drug, particularly in the large intestine, where it counteracts nonspecific diarrhea and treats irritable bowel syndrome. Veterinarians prescribe this drug for periodontal disease, tetanus and pancreatic insufficiency with small intestinal bacterial overgrowth (SIBO).
  
  

Common Side Effects

• Metronidazole is usually tolerated better if given with food because it can be bitter and dogs may develop an aversion to it. The most common side effects in dogs are reactions to the bitter taste, mild stomach upset and decreased appetite. When taking it, some dogs exhibit excessive salivation, gagging, reflux, mouth pawing, nausea or vomiting.
  
  

Less Common Side Effects

• More serious, less common side effects of metronidazole include diarrhea, depression, weakness, low white blood cell count, blood in the urine and liver complications. Signs of toxicity, if present, tend to begin seven to 12 days after the beginning of treatment. In most cases, these side effects resolve in a matter of days after stopping the medication.
  
  

Neurological Side Effects

• Some dogs suffer from neurological side effects, such as nystagmus (unintentional eye movement), dilated pupils, ataxia (lack of coordination) head-tilt, tremors, disorientation, stiffness and even seizures. These more alarming symptoms may be seen in dogs who have been prescribed long-term moderate to high-dose therapy for treatment of difficult bacterial infections like SIBO.
  
  One neurologist examining a symptomatic dog informed the dog's owner that he rarely saw a dog with metronidazole toxicity return to normal and that some had permanent brain damage. Although dogs compensate and learn to live with acquired disabilities, these neurological symptoms can worsen when a dog is sick or stressed.
  
  

Cases of Metronidazole Toxicity

• SIBO is one of those stubborn conditions. Dogs who have it may require long-term metronidazole treatment and some have experienced serious side effects.
  
  

Pre-Existing Conditions

• Before you give your dog metronidazole, make sure your veterinarian knows what other drugs your dog has been taking. Your dog's liver function should be tested and monitored, and, if your dog already has liver disease, it should not be prescribed. There is a possibility that dogs with tick-related diseases may be more susceptible to metronidazole toxicity, because both can affect liver function.
  
  

Diagnosis, Treatment and Prognosis

• There are no home remedies for metronidazole poisoning. If you even suspect this drug as a possible cause for symptoms your dog is exhibiting, immediately contact your veterinarian or an emergency animal clinic. A diagnosis of metronidazole toxicity is based on a physical exam and a thorough history of recent drug intake and pre-exisiting conditions. Blood tests to measure the toxicity of this drug have not been shown to be effective.
  
  The initial treatment for metronidazole toxicity is immediate withdrawal of the drug. Some dogs may need to be hospitalized and given intravenous fluids as well as intravenous Diazepam. An emetic to stop vomiting may also be needed. Blood tests should be conducted to evaluate the function of the dog's liver and kidneys. There is no known antidote for metronidazole poisoning and recovery may take one to two weeks or longer. Unfortunately, dogs who are severely affected may not survive.