Drug reference

Ornidazole

5-nitroimidazole antiprotozoal and antibacterial agent · Antibiotic

Also known as Ornidazole hydrochloride

START

Confirm anaerobic/protozoal indication. Rule out first-trimester pregnancy. Counsel on alcohol abstinence (disulfiram-like reaction).

TYPICAL MAX

Do not exceed 2g/day. Limit duration to ≤10 days unless essential (neuropathy risk).

STOP IF

Signs of peripheral neuropathy (numbness, tingling), seizures, severe rash, jaundice, severe leukopenia.

WATCH

CNS effects (dizziness, ataxia, seizures)—more common with higher doses and longer duration. Alcohol must be avoided during and for 3 days after treatment. Dark urine is expected and harmless.

CDSCO approvedJan AushadhiATC P01AB03

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 1h · Onset within 1-2 hours
PEAK: 1.5h · Tmax ~1-2 hours
t½: 13h · t½ ~12-14 hours
DURATION: 12h · 12 hours (BID)

EXCRETION

Renal as metabolites (~65%)

route + CYP

INTERACTIONS

1 major

SEVERE in our sources

PREGNANCY

Avoid in first trimester (no adequate human data; animal studies show teratogenicity at high doses). Second and third trimesters: use only if clearly needed.

FDA category + note

Top interactionssee all 5 →

BusulfanSevereDatabaseKimi deep-research + Cla

Available in India

59 branded formulations and 61 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Jan Aushadhi — generic available at GoI pharmacies

Mechanism

After intracellular reduction of the nitro group by low-redox-potential electron transport proteins, toxic reduction products interact with microbial DNA, causing strand breakage and loss of helical structure, leading to cell death. Active against anaerobic bacteria and protozoa.

Indications

Amoebiasis (intestinal and hepatic)GiardiasisTrichomoniasisBacterial vaginosisAnaerobic bacterial infections (intra-abdominal, CNS, bone, pelvic)Surgical prophylaxis (anaerobic coverage)H. pylori eradication (combination therapy)

Dosing

Adult: Amoebiasis: 500mg PO BID x 5-10 days. Giardiasis: 1.5g PO once daily x 1-2 days. Trichomoniasis: 1.5g PO single dose or 500mg BID x 5 days. Anaerobic infections: 1g IV/PO loading, then 500mg BID. Surgical prophylaxis: 1g IV 30 min pre-op.
Pediatric: Amoebiasis/giardiasis: 25-40mg/kg/day divided BID. Max 1.5g/day.
Renal adjustment: No adjustment needed (hepatically metabolized).
Hepatic adjustment: Reduce dose by 50% in severe hepatic impairment; monitor for toxicity.
Geriatric: No specific adjustment; monitor for CNS side effects.
Max dose: 1.5g single dose; 2g/day (divided)

Pharmacokinetics

Onset

Rapid; antiprotozoal effect within hours

Peak effect

Tmax 1-2 hours (PO); tissue penetration excellent including CNS

Duration

12 hours (BID dosing)

Half-life

~12-14 hours (allows BID dosing vs metronidazole QID)

Bioavailability

~90%

Protein binding

~15%

Metabolism

Hepatic via oxidation, hydroxylation, and glucuronidation; CYP3A4 and CYP2C9 involved

Excretion

~60-70% renal (metabolites + ~15% unchanged); ~20% fecal

Contraindications

Hypersensitivity to nitroimidazoles (metronidazole, tinidazole)
First trimester of pregnancy
Severe hepatic impairment
Blood dyscrasias
CNS disorders (epilepsy, multiple sclerosis—relative)

Side effects

Common

Metallic tasteNausea and vomitingEpigastric discomfortHeadacheDizzinessDry mouthDark urine discoloration (harmless)

Serious

Peripheral neuropathy (with prolonged use >10 days)
Seizures
Leukopenia
Hepatotoxicity
Severe cutaneous reactions
Pancreatitis (rare)

Pregnancy & lactation

Pregnancy

Avoid in first trimester (no adequate human data; animal studies show teratogenicity at high doses). Second and third trimesters: use only if clearly needed.

Lactation

Excreted in breast milk; concentrations similar to plasma. Discontinue breastfeeding during treatment and for 3 days after last dose.