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Metronidazole

PrescriptionCDSCO approved
Nitroimidazole antibiotic
Last reviewed 19 Apr 2026 · PetCare.AI Editorial Team
Species
Dog, Cat
Brands
3 available
Interactions
6 documented
Formulations
4

Mechanism of action

Disrupts DNA synthesis in anaerobic bacteria and protozoa

At a glance

Class
Nitroimidazole antibiotic
Schedule
Prescription
Storage
Store below 25°C, protect from light and moisture
CDSCO (India)
Vet-approved — 1980-01

Dosing

🐕

Dog

Anaerobic infections
Dose
10–25 mg/kg
Route
PO
Frequency
BID
Max dose
750 mg/dose; 1500 mg/day
Duration: 5-7 days
Giardiasis
Dose
15–25 mg/kg
Route
PO
Frequency
BID
Max dose
750 mg/dose; 1500 mg/day
Duration: 5-7 days
🐈

Cat

Anaerobic infections
Dose
10–15 mg/kg
Route
PO
Frequency
BID
Max dose
375 mg/dose; 750 mg/day
Duration: 5-7 days
Inflammatory bowel disease
Dose
10–20 mg/kg
Route
PO
Frequency
BID
Max dose
375 mg/dose; 750 mg/day
Duration: 14-28 days

Formulations

💊

Tablet — 2

Strength
200mg
Available in India
Strength
400mg
Available in India
🧴

Suspension — 1

Strength
200mg/5mL
Available in India
💉

Injectable — 1

Strength
5mg/mL
Available in India

Storage

Store below 25°C, protect from light and moisture

Safety

Absolute contraindications — do not use

  • Known hypersensitivity
    Do not use in animals with known metronidazole hypersensitivity

Use with caution

  • Hepatic impairment
    Reduce dose or avoid in severe hepatic dysfunction — drug is hepatically metabolized
  • Pregnancy
    Teratogenic in lab animals — avoid in first trimester

Adverse effects

Common
Nausea
Vomiting
Anorexia
Diarrhoea
Serious
Neurotoxicity (ataxia, seizures at high doses)
Hepatotoxicity

Monitoring parameters

Neurological signsLiver enzymes (ALT, ALP) for prolonged courses

Interactions

Major — 2

Warfarin
major
Metronidazole inhibits CYP2C9 metabolism of warfarin's more active S-enantiomer, increasing warfarin effect and hemorrhage risk.
Management: Reduce warfarin dose by 25-50% when adding metronidazole. Monitor PT/INR every 2-3 days during metronidazole course.
Ethanol (Medical Grade)
major
Metronidazole inhibits aldehyde dehydrogenase, causing acetaldehyde accumulation with ethanol: severe nausea, vomiting, cramping, tachycardia (disulfiram-like reaction).
Management: Do not combine. If ethanol used as EG antidote in patient on metronidazole, use fomepizole instead.

Moderate — 3

Tramadol
moderate
Both drugs lower seizure threshold; combined use increases CNS depression risk
Management: Monitor closely for neurological signs. Consider dose reduction of tramadol.
Vincristine
moderate
Both can cause peripheral neuropathy; additive neurotoxic risk
Management: Monitor for signs of peripheral neuropathy (weakness, ataxia). Avoid prolonged concurrent use.
Phenobarbital
moderate
Phenobarbital induces hepatic CYP enzymes, increasing metronidazole metabolism and reducing its efficacy.
Management: May need to increase metronidazole dose. Monitor clinical response.

Minor — 1

Prednisolone
minor
Corticosteroids may mask signs of infection; no direct pharmacokinetic interaction
Management: Monitor for signs of GI irritation. Acceptable combination with monitoring.

Brands

International

Flagyl
Abbott

India

Metrogyl
J&J
Metris
Intas

FAQs

Frequently asked questions

›What is Metronidazole?
Metronidazole is a nitroimidazole antibiotic used in pets. Disrupts DNA synthesis in anaerobic bacteria and protozoa
›What is Metronidazole used for in pets?
Metronidazole is used in veterinary medicine for: Anaerobic infections; Giardiasis; Inflammatory bowel disease.
›What is the Metronidazole dose for dogs?
For dogs, Metronidazole is typically dosed as follows — Anaerobic infections: 10–25 mg/kg PO BID; Giardiasis: 15–25 mg/kg PO BID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Metronidazole dose for cats?
For cats, Metronidazole is typically dosed as follows — Anaerobic infections: 10–15 mg/kg PO BID; Inflammatory bowel disease: 10–20 mg/kg PO BID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What are the side effects of Metronidazole?
Common: Nausea, Vomiting, Anorexia, Diarrhoea. Serious (call your vet immediately): Neurotoxicity (ataxia, seizures at high doses), Hepatotoxicity.
›Does Metronidazole need a prescription?
Yes. Metronidazole is a prescription medication and should only be administered under veterinary supervision.
›When should Metronidazole not be used?
Do not use Metronidazole if: Known hypersensitivity.

References

References

Textbooks & handbooks

  • Plumb, D.C. Plumb's Veterinary Drug Handbook. 10th ed., Wiley-Blackwell, 2023.
  • Vail, D.M., Thamm, D.H., & Liptak, J.M. (eds.). Withrow & MacEwen's Small Animal Clinical Oncology. 6th ed., Saunders/Elsevier, 2020.
  • Riviere, J.E., & Papich, M.G. (eds.). Veterinary Pharmacology and Therapeutics. 10th ed., Wiley-Blackwell, 2018.
  • National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, Washington DC, 2006.
  • The Merck Veterinary Manual. Merck & Co., Online edition. https://www.merckvetmanual.com/

Clinical guidelines & consensus

  • Fletcher, D.J., Boller, M., Brainard, B.M., et al. "RECOVER Evidence and Knowledge Gap Analysis on Veterinary CPR." Journal of Veterinary Emergency and Critical Care, 2012;22(S1):S102–S131.
  • American Animal Hospital Association. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. AAHA Press.

Journals & peer-reviewed studies

  • Hogan, D.F., Fox, P.R., Jacob, K., et al. "Secondary prevention of cardiogenic arterial thromboembolism in the cat: The FAT CAT study." Journal of Veterinary Cardiology, 2015;17(Suppl 1):S306–S317.
  • Boswood, A., Häggström, J., Gordon, S.G., et al. "Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study — A Randomized Clinical Trial." Journal of Veterinary Internal Medicine, 2016;30(6):1765–1779.
  • ASPCA Animal Poison Control Center. Toxicology and Poison Management Guidelines. American Society for the Prevention of Cruelty to Animals. https://www.aspca.org/pet-care/animal-poison-control

Regulatory & approvals

  • Central Drugs Standard Control Organisation (CDSCO), Government of India. Veterinary Drug Approval Registry, 1969–2026. Directorate General of Health Services. https://cdsco.gov.in/

Databases

  • Washington State University, College of Veterinary Medicine. Veterinary Clinical Pharmacology Laboratory (VCPL) — MDR1 Multidrug Sensitivity Database. https://vcpl.vetmed.wsu.edu/
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →