Schedule H

Oral, Intravenous

• Tablets: 500 mg

• Infusion: 500 mg/100 mL

INDICATIONS + DOSING — FOR CLINICIAN USE ONLY

Primary Indications (Approved / Standard in India)

1. Intestinal Amoebiasis (Amoebic Dysentery)

Adults — Oral:

Parameter Dosing

Starting dose 500 mg twice daily with meals

Titration Not applicable

Usual maintenance dose 500 mg twice daily

Maximum dose 1500 mg/day

Duration 5–10 days

Adults — Intravenous (when oral not tolerated):

Parameter Dosing

Starting dose 500 mg IV infusion twice daily

Titration Not applicable

Usual maintenance dose 500 mg twice daily

Maximum dose 1000 mg/day IV

Duration Switch to oral as soon as feasible

1. Amoebic Liver Abscess

Adults — Oral:

Parameter Dosing

Starting dose 500 mg twice daily

Titration Not applicable

Usual maintenance dose 500 mg twice daily

Maximum dose 1500 mg/day

Duration 5–10 days (often shorter 5–7 days adequate)

Clinical Notes:

• Often used in combination with aspiration for large abscesses (>5 cm)

• IV route preferred initially in severe cases

1. Giardiasis

Adults — Oral:

Parameter Dosing

Starting dose 1500 mg as single dose OR 500 mg twice daily

Titration Not applicable

Usual maintenance dose 500 mg twice daily if multi-day regimen

Maximum dose 1500 mg/day

Duration Single dose therapy OR 5 days

Clinical Notes:

• Administer after meals to reduce gastrointestinal upset

• Single-dose regimen preferred for compliance

1. Trichomoniasis

Adults — Oral:

Parameter Dosing

Starting dose 1500 mg as single dose OR 500 mg twice daily

Titration Not applicable

Usual maintenance dose 500 mg twice daily if multi-day regimen

Maximum dose 1500 mg/day

Duration Single dose OR 5 days

Clinical Notes:

• Treat sexual partner concurrently

• Abstain from sexual intercourse until both partners treated

1. Anaerobic Bacterial Infections (Pelvic infections, Intra-abdominal sepsis, Post-operative infections)

Adults — Oral or IV:

Parameter Dosing

Starting dose 500 mg twice daily (oral or IV)

Titration Increase to 1000 mg twice daily in severe infections

Usual maintenance dose 500 mg twice daily

Maximum dose 2000 mg/day

Duration 5–10 days depending on clinical response

1. Surgical Prophylaxis (Anaerobic Coverage)

PAEDIATRIC DOSING (Specialist Only)

Primary Indications (Approved / Standard in India)

1. Intestinal Amoebiasis and Amoebic Liver Abscess

Weight/Age Starting Dose Usual Maintenance Dose Maximum Dose Duration

Children ≥3 years 25 mg/kg/day in single dose or divided doses 25 mg/kg/day 1500 mg/day 5–10 days

Titration: Not applicable

1. Giardiasis

Weight/Age Starting Dose Usual Maintenance Dose Maximum Dose Duration

Children ≥3 years 40 mg/kg as single dose Not applicable (single-dose regimen) 1500 mg Single dose

Alternative regimen 25 mg/kg/day divided twice daily 25 mg/kg/day 1000 mg/day 5 days

1. Anaerobic Infections

Weight/Age Starting Dose Usual Maintenance Dose Maximum Dose Duration

Children ≥3 years 20–30 mg/kg/day in 2 divided doses 20–30 mg/kg/day 1500 mg/day 5–10 days

Titration: Not applicable

Safety Monitoring:

• Monitor for neurological symptoms (dizziness, ataxia)

• Assess gastrointestinal tolerance

• Avoid prolonged courses (>10 days)

Secondary Indications – Paediatrics (Off-label)

Not established for Clostridioides difficile or other non-protozoal infections in children.

Clear Statement: Not recommended for use in children below 3 years of age except under paediatric infectious disease specialist supervision.

• Known hypersensitivity to ornidazole or other nitroimidazole derivatives (metronidazole, tinidazole, secnidazole)

• Active CNS disorders including epilepsy or history of seizures

• Concurrent use with disulfiram

• First trimester of pregnancy

• History of blood dyscrasias

• Peripheral neuropathy (pre-existing or developing during therapy)

• Prolonged therapy beyond 10 days (neuropathy risk)

• Hepatic impairment

• Concurrent alcohol consumption (disulfiram-like reaction)

• Elderly patients (increased CNS adverse effect risk)

• Concurrent use of QT-prolonging medications

Parameter Details

Safety Statement Contraindicated in first trimester; use in second and third trimester only if benefit clearly outweighs risk

Preferred alternatives Metronidazole (better safety data in pregnancy if treatment essential)

When may be used Second/third trimester for severe protozoal infections when alternatives not suitable

What to monitor Fetal growth monitoring if prolonged course used

Parameter Details

Compatible with breastfeeding Likely compatible at standard doses; drug excreted in breast milk

Preferred alternatives Metronidazole (more established safety data)

Expected drug levels in milk Low to moderate

What to monitor in infant Gastrointestinal upset, oral thrush, feeding difficulties

Note: For single high-dose therapy (1500 mg), consider expressing and discarding milk for 24 hours after dose.

Parameter Recommendation

Starting dose 500 mg once daily; titrate based on tolerance

Titration Slower titration advised; assess response before increasing

Extra risks Increased susceptibility to CNS adverse effects (dizziness, ataxia, confusion); falls risk; reduced hepatic reserve

Monitoring Assess renal and hepatic function before and during therapy

Interacting Drug Effect Management

Alcohol Disulfiram-like reaction (flushing, nausea, vomiting, tachycardia) Avoid alcohol during therapy and for 48 hours after completion

Disulfiram Risk of acute psychosis and confusion Contraindicated; do not use concurrently

Warfarin Enhanced anticoagulant effect via CYP inhibition Monitor INR closely; may require warfarin dose reduction

Phenytoin Increased phenytoin levels; toxicity risk Monitor phenytoin levels; adjust dose as needed

Phenobarbital Reduced ornidazole efficacy due to enhanced metabolism Consider alternative antiprotozoal or increase monitoring

Interacting Drug Effect Management

Lithium Increased lithium levels; toxicity risk Monitor lithium levels and renal function

Fluoroquinolones (ciprofloxacin, levofloxacin) Additive QT prolongation risk Use with caution; ECG monitoring in high-risk patients

Carbamazepine Potential increase in carbamazepine levels Monitor for toxicity; consider level monitoring

Cyclosporine, Tacrolimus May increase calcineurin inhibitor levels Monitor trough levels

5-Fluorouracil Reduced 5-FU clearance; increased toxicity Avoid concurrent use if possible

• Nausea and vomiting

• Metallic taste

• Headache

• Dizziness

• Diarrhoea

• Abdominal discomfort

• Dry mouth

• Fatigue

Adverse Effect Notes

Seizures Higher risk with CNS disorders, high doses, or prolonged therapy; discontinue immediately

Peripheral neuropathy Numbness, tingling, paraesthesias; more common with courses >10 days; may be irreversible

Encephalopathy Rare; presents as confusion, ataxia, dysarthria; discontinue immediately

Stevens-Johnson syndrome / Toxic epidermal necrolysis Rare; discontinue and hospitalise

Hepatotoxicity Idiosyncratic; monitor LFTs if suspected

Leukopenia Rare; monitor CBC if prolonged therapy

During therapy LFTs if treatment exceeds 7 days; clinical monitoring for neuropathic symptoms

If on warfarin INR monitoring at initiation and during therapy

Long-term Avoid courses exceeding 10 days; if unavoidable, specialist supervision with neurological assessment required

Single-agent formulations:

• Dazolic (Sun Pharma)

• Ornida (Zydus Cadila)

• Orni (Mankind)

• Ornigyl (J.B. Chemicals)

• Ornidazole IP (various generic manufacturers)

Fixed-dose combinations (commonly available):

• Norfloxacin + Ornidazole

• Cefixime + Ornidazole

Note: FDCs should be used judiciously; rational use of single-agent therapy preferred when appropriate.

NLEM Status: Not listed under NLEM 2022

• Shorter courses are often adequate: Single-dose therapy (1500 mg) is highly effective for giardiasis and trichomoniasis — avoid unnecessary prolonged courses

• FDC use should be rational: Ofloxacin-ornidazole FDCs are commonly prescribed for acute diarrhoea but should be reserved for cases with documented or highly suspected mixed bacterial-protozoal aetiology

• CNS profile: Although generally considered to have fewer CNS effects than metronidazole, seizures and neuropathy still occur — avoid in epilepsy and monitor for neurological symptoms

• Alcohol counselling is essential: Clearly advise patients to avoid alcohol during therapy and for 48 hours after completion

• Switch to oral early: IV formulation should be used only when oral intake is not possible; switch to oral as soon as tolerated

• Avoid prolonged therapy: Courses exceeding 10 days significantly increase peripheral neuropathy risk

ornidazole; amoebiasis; giardiasis; trichomoniasis; anaerobic infection; nitroimidazole; antiprotozoal; surgical prophylaxis; alcohol-interaction; Schedule H

RxIndia v1.0 — 10 Jun 2025

• CDSCO approved product information

• Indian Pharmacopoeia

• API Textbook of Medicine, 11th Edition

• ICMR Treatment Guidelines for Antimicrobial Use in Common Syndromes

• AIIMS Antimicrobial Guidelines

• National Guidelines on Diarrhoeal Disease Management

• IAP Guidelines (for paediatric dosing)

• WHO Model Formulary (supportive reference)

• Goodman & Gilman's The Pharmacological Basis of Therapeutics