What Are The Possible Side Effects of Metronidazole?
Most medications have the potential to cause side effects, so it’s important to ask your veterinarian what to watch out for. Metronidazole has a very bitter taste and often causes excessive salivation, drooling, gagging, or frothing at the mouth, especially in cats. In both cats and dogs, the bitter taste may also cause nausea and loss of appetite (anorexia), so pets taking metronidazole may eat less than usual or refuse meals altogether. Vomiting and diarrhea are also relatively common side effects of this drug.
More serious but less common adverse effects of metronidazole in pets include lethargy, weakness, liver damage, and central nervous system disorders. Clinical signs of nervous system toxicity may include abnormal eye movements, head tilt, loss of balance and coordination, stumbling or knuckling, and even seizures.
Some cases of birth defects have been recorded. Rare idiosyncratic reactions in dogs have included low blood counts. In cats, metronidazole has been found to cause DNA damage to lymphocytes (white blood cells), an important element of the immune system.
Questions to Ask If Your Veterinarian Prescribes Metronidazole
While metronidazole has been shown to be an appropriate choice for some conditions, in other cases, it may not be as effective as many veterinarians assume. We recommend that you talk with your veterinarian about whether metronidazole will be beneficial for your dog. Here are some questions to ask:
In many cases of dog diarrhea, the answer may be no. Though some health issues, such as life-threatening bacterial infections, do require antibiotics, other conditions may resolve with supportive care alone.
For example, dogs with bloody diarrhea (hemorrhagic gastroenteritis) are often given antibiotics, but according to veterinary consensus guidelines, antibiotics are appropriate for this condition only when sepsis is present. Researchers have found that as long as sepsis is not involved, even hemorrhagic gastroenteritis responds just as well to supportive care as to antibiotics.
In fact, several studies have shown that metronidazole can actually make diarrhea worse, not only by reducing populations of “good” anaerobic bacteria but also by altering the intestinal mucus.
What can cause metronidazole not to work?
It will not work for viral infections (e.g., common cold, flu). Unnecessary use or overuse of any antibiotic can lead to its decreased effectiveness. Metronidazole can also be used in combination with anti-ulcer medications to treat certain types of stomach ulcers.