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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

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

Frequency

BID

Max dose

750 mg/dose; 1500 mg/day

Duration: 5-7 days

Giardiasis

Dose

15–25 mg/kg

Route

Frequency

BID

Max dose

750 mg/dose; 1500 mg/day

Duration: 5-7 days

🐈

Cat

Anaerobic infections

Dose

10–15 mg/kg

Route

Frequency

BID

Max dose

375 mg/dose; 750 mg/day

Duration: 5-7 days

Inflammatory bowel disease

Dose

10–20 mg/kg

Route

Frequency

BID

Max dose

375 mg/dose; 750 mg/day

Duration: 14-28 days

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 →

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

Educational reference only

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.

Educational reference only

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.

Educational reference only

References

The PetCare.AI drug reference is built from 13 authoritative sources cited across 580 drug monographs.

Textbooks & handbooks — 5

Plumb's Veterinary Drug Handbook
Withrow & MacEwen's Small Animal Clinical Oncology
Merck Veterinary Manual
NRC Nutrient Requirements of Dogs and Cats
Veterinary Pharmacology and Therapeutics (Riviere & Papich)

Clinical guidelines & consensus — 4

ASPCA Animal Poison Control Center Guidelines
AAHA Diabetes Management Guidelines
ASPCA Poison Control Guidelines
RECOVER CPR Guidelines

Journals & peer-reviewed studies — 2

EPIC Study (J Vet Intern Med 2016)
JVIM FAT CAT Study

Regulatory & approvals — 1

CDSCO Veterinary Drug Approval Registry (1969–2026)

Databases — 1

Washington State University VCPL MDR1 Database