Schedule H

Oral

Form Strengths Available

Tablet 500 mg, 1000 mg

Sachet (granules for oral suspension) 2 g

INDICATIONS + DOSING — FOR CLINICIAN USE ONLY

Primary Indications (Approved / Standard in India)

1. Amoebiasis (Intestinal and Hepatic)

Parameter Details

Starting dose 2 g orally as single dose after food

Titration Not applicable

Usual maintenance dose Single-dose therapy (no maintenance required)

Maximum dose 2 g as single dose

Clinical Notes:

• Effective against both luminal and invasive forms of Entamoeba histolytica

• Combine with luminal agent (diloxanide furoate 500 mg TDS × 10 days) for complete eradication in invasive disease

• For hepatic amoebiasis: Single 2 g dose usually sufficient; repeat after 48–72 hours if clinical response inadequate

1. Giardiasis

Parameter Details

Starting dose 2 g orally as single dose after food

Titration Not applicable

Usual maintenance dose Single-dose therapy (no maintenance required)

Maximum dose 2 g as single dose

Clinical Notes:

• High cure rates (>90%) against Giardia lamblia

• Preferred over multi-day metronidazole regimen for better compliance

• Ensure stool examination follow-up at 2–4 weeks to confirm cure

1. Bacterial Vaginosis

Parameter Details

Starting dose 2 g orally as single dose

Titration Not applicable

Usual maintenance dose Single-dose therapy (no maintenance required)

Maximum dose 2 g as single dose

Clinical Notes:

• Use in non-pregnant women only

• Alternative to metronidazole in patients with poor compliance or recurrence

• Not for routine use in pregnancy (refer to Pregnancy section)

Secondary Indications — Adults (Off-label)

Indication Dose Duration Notes

Trichomoniasis 2 g orally as single dose Single dose OFF-LABEL; Alternative to metronidazole; Treat sexual partner simultaneously; Evidence: International meta-analyses, occasional Indian specialist practice

PAEDIATRIC DOSING (Specialist Only)

Primary Indications (Approved / Standard in India)

1. Giardiasis

Weight Range Starting Dose Route Frequency Maximum Dose

10–15 kg 30 mg/kg Oral (tablet/sachet) Single dose 1 g

15–30 kg 1 g Oral Single dose 1 g

30 kg 2 g Oral Single dose 2 g

Parameter Details

Starting dose Weight-based as per table above

Titration Not applicable

Usual maintenance dose Single-dose therapy (no maintenance required)

Maximum dose 2 g

1. Acute Intestinal Amoebiasis

Weight Range Starting Dose Route Frequency Maximum Dose

10–15 kg 30 mg/kg Oral (tablet/sachet) Single dose 1 g

15–30 kg 1 g Oral Single dose 1 g

30 kg 2 g Oral Single dose 2 g

Parameter Details

Starting dose Weight-based as per table above

Titration Not applicable

Usual maintenance dose Single-dose therapy (no maintenance required)

Maximum dose 2 g

Clinical Notes:

• Administer after food

• Ensure adequate hydration

• Combine with luminal agent (diloxanide furoate) if invasive disease suspected

Safety Monitoring:

• Monitor for GI intolerance (nausea, vomiting)

• Watch for CNS symptoms (headache, dizziness)

• Check for signs of peripheral neuropathy in case of repeated dosing

Minimum Age Statement

⚠️ Not recommended in children <2 years due to limited safety and efficacy data. Use only under paediatric specialist supervision if absolutely necessary in this age group.

Secondary Indications — Paediatrics (Off-label)

Indication Dose Notes

Bacterial vaginosis Not applicable Not used in paediatric population

Trichomoniasis Not recommended Specialist only if absolutely necessary; Limited paediatric data

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

• Active or history of CNS disorders (epilepsy, history of seizures)

• Severe hepatic impairment

• First trimester of pregnancy

• Concurrent disulfiram therapy (within 2 weeks)

• History of blood dyscrasias (risk of bone marrow suppression with nitroimidazoles)

• Pre-existing peripheral neuropathy or optic neuropathy

• Alcohol consumption: Strictly avoid alcohol for ≥72 hours after dose (risk of disulfiram-like reaction — class effect)

• Patients on QT-prolonging medications (theoretical concern, limited evidence)

• History of Candida infections (may precipitate vaginal candidiasis)

Aspect Details

Overall Safety Avoid in first trimester; Insufficient human safety data

First Trimester Contraindicated

Second/Third Trimester Use only if benefit clearly outweighs risk; Specialist input advised

Preferred Alternatives Metronidazole (more extensive safety data in pregnancy)

Monitoring Fetal growth monitoring; Maternal liver function tests

Note: Secnidazole crosses the placenta; Long half-life (~17–29 hours) results in prolonged fetal exposure compared to metronidazole

Aspect Details

Compatible with Breastfeeding Use with caution; Limited data available

Drug Levels in Milk Low to moderate (excreted in small amounts)

Preferred Alternatives Metronidazole (shorter half-life, more extensively studied)

Manufacturer Recommendation Avoid breastfeeding for 3–4 days after single 2 g dose

Infant Monitoring GI disturbance (diarrhoea, vomiting), oral/diaper candidiasis

Aspect Recommendation

Starting dose 2 g single dose (same as younger adults)

Titration Not applicable (single-dose therapy)

Special Considerations Slower hepatic metabolism may prolong half-life

Monitoring CNS effects (confusion, dizziness); Ensure adequate hydration

Dose Adjustment No routine adjustment if hepatic and renal function normal

Interacting Drug Mechanism/Effect Management

Alcohol (ethanol) Disulfiram-like reaction (flushing, nausea, headache, palpitations) Avoid alcohol during and for ≥72 hours after dose

Disulfiram Risk of acute psychosis and confusional states Contraindicated — do not co-administer; Minimum 2-week gap

Warfarin Enhanced anticoagulant effect (CYP inhibition) Monitor INR closely; May need warfarin dose reduction

Carbamazepine/Phenytoin CYP induction → Reduced secnidazole efficacy Consider alternative antiparasitic or monitor clinical response

Interacting Drug Effect Management

Cimetidine May increase nitroimidazole levels via reduced hepatic clearance Monitor for increased adverse effects

Lithium Potential for increased lithium toxicity Monitor lithium levels if co-administered

Oral contraceptives Diarrhoea may reduce OC absorption and efficacy Advise additional contraceptive precautions

Fluoroquinolones Theoretical additive neurotoxicity risk Monitor for CNS symptoms

• Nausea (most common)

• Metallic taste in mouth

• Abdominal discomfort/pain

• Headache

• Dizziness

• Anorexia

• Vaginal candidiasis (when used for bacterial vaginosis)

• Dry mouth

Adverse Effect Clinical Action

Seizures Rare; More likely with high doses or hepatic dysfunction — Discontinue immediately

Peripheral neuropathy Paraesthesia, numbness; Usually with prolonged/repeated exposure — Discontinue and do not re-challenge

Stevens-Johnson Syndrome (SJS) Very rare — Stop immediately; Urgent dermatology referral

Leukopenia/Agranulocytosis Monitor if signs of unexplained infection — Check CBC urgently

Encephalopathy Confusion, ataxia (rare) — Discontinue; Supportive care

After initiation Watch for CNS symptoms (seizures, confusion, dizziness); GI intolerance

Long-term Not applicable — Single-dose regimen; Avoid repeated/chronic use

Brand Name Manufacturer Notes

Secnil Zydus Cadila Tablet/Sachet

Secnil Forte Zydus Cadila 1000 mg tablet

Sebicula Abbott Sachet formulation

Secnigyl Omega Tablet

Enidazole Alembic Tablet

FDC Note: Some irrational FDCs exist in market (e.g., with fluconazole/clavulanic acid) — Not recommended as per standard Indian guidelines

NLEM Status: NOT included in NLEM; Not under NPPA ceiling pricing

1. Compliance advantage: Single-dose 2 g regimen offers superior compliance compared to 5–7 day metronidazole courses — Preferred in patients with adherence concerns

1. Not for chronic use: Long half-life (~17–29 hours) means drug accumulates with repeated dosing — Avoid using secnidazole repeatedly or chronically to minimize neurotoxicity risk

1. Luminal agent essential: For invasive amoebiasis, always follow secnidazole with diloxanide furoate (500 mg TDS × 10 days) to eliminate cyst carriage

1. Alcohol warning critical: Counsel patients explicitly about strict alcohol avoidance for at least 72 hours post-dose (longer window than metronidazole due to prolonged half-life)

1. Pregnancy consideration: When treatment cannot be delayed in pregnant women (2nd/3rd trimester), metronidazole remains preferred over secnidazole due to more extensive safety data

1. Avoid empirical use: Reserve for confirmed protozoal infections — Do not use empirically for non-specific diarrhoea (contributes to antimicrobial resistance)

secnidazole; nitroimidazole; antiprotozoal; amoebiasis; giardiasis; bacterial vaginosis; single-dose therapy; Schedule H; CNS caution; alcohol-avoid

RxIndia v1.0 — 28 Apr 2025

• CDSCO Drug Database

• National Formulary of India (NFI)

• Indian Pharmacopoeia

• API Textbook of Medicine

• AIIMS Delhi Antimicrobial Policy

• IAP Textbook of Paediatrics

• Goodman & Gilman's The Pharmacological Basis of Therapeutics

• Indian Journal of Pharmacology (clinical reviews)

• Select international RCT/meta-analysis (for off-label trichomoniasis indication only)