1. Clinical & Scientific Overview
Ornidazole & Tinidazole IP (TIP-MED-000325, Reference Code [8.11]-CMP55) is classified under
Antimicrobials — Antibacterial & Antibiotic Agents (Ch 08) as a 5-Nitroimidazole Antiprotozoal & Anaerobic Bactericidal Antibiotic (Free-Radical DNA Strand Breaker; WHO 'Access' Group).
Within the Indian regulatory and compendial framework, it is governed under Schedule H Prescription Drug (To be sold by retail on the prescription of a Registered Medical Practitioner only — Drugs Rules 1945).
Longer-half-life 5-nitroimidazole comparators (t1/2 12–14 hr) in amoebiasis, giardiasis, and anaerobic infections.
Standard approved strengths (refer to comparative context)
3. Mechanism of Action & Pharmacodynamics
Longer-half-life 5-nitroimidazole comparators (t1/2 12–14 hr) in amoebiasis, giardiasis, and anaerobic infections.
4. Therapeutic Indications & Evidence-Supported Uses
- Intestinal and hepatic amoebiasis (Entamoeba histolytica—400–800 mg TDS for 5–10 days), giardiasis (200–400 mg TDS for 5–7 days), trichomoniasis and bacterial vaginosis, anaerobic dental/periodontal infections, intra-abdominal/pelvic anaerobic sepsis, H
- pylori eradication, and mild non-severe C
- difficile infection (when vancomycin/fidaxomicin is unavailable)
🇮🇳 Jurisdiction & Indication Note: Indications and schedules reflect Indian compendial and regulatory records (CDSCO / Indian Pharmacopoeia & NFI / NLEM 2022). Where international reference labels (US FDA DailyMed / NCBI StatPearls) are cited for pharmacokinetic or mechanistic parameters, international approvals do not automatically imply CDSCO approval in India.
5. Educational Dosage Context, Formulations & Administration
Educational Dosing & Regimen Summary: Longer-half-life 5-nitroimidazole comparators (t1/2 12–14 hr) in amoebiasis, giardiasis, and anaerobic infections.
Administration & Meal Timing: Take WITH or immediately AFTER food with a full glass of water (significantly reduces nausea, epigastric cramping, and metallic taste). | Three times daily after breakfast, lunch, and dinner (every 8 hours).
6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment
Comparative pharmacokinetic profile co-indexed under [8.11].
Renal: Parent drug unchanged in mild-moderate CKD, but active hydroxy-metabolites accumulate in CrCl <10 mL/min or haemodialysis (supplement post-dialysis or reduce by 50% in prolonged courses). Hepatic: Metabolised (>60%) by hepatic oxidation/glucuronidation — in severe hepatic impairment (Child-Pugh C cirrhosis), REDUCE TOTAL DAILY DOSE BY 50% (e.g., 400 mg every 12h instead of TDS) to prevent cerebellar ataxia and encephalopathy.
Renal: Parent drug unchanged in mild-moderate CKD, but active hydroxy-metabolites accumulate in CrCl <10 mL/min or haemodialysis (supplement post-dialysis or reduce by 50% in prolonged courses). Hepatic: Metabolised (>60%) by hepatic oxidation/glucuronidation — in severe hepatic impairment (Child-Pugh C cirrhosis), REDUCE TOTAL DAILY DOSE BY 50% (e.g., 400 mg every 12h instead of TDS) to prevent cerebellar ataxia and encephalopathy.
Renal: Parent drug unchanged in mild-moderate CKD, but active hydroxy-metabolites accumulate in CrCl <10 mL/min or haemodialysis (supplement post-dialysis or reduce by 50% in prolonged courses). Hepatic: Metabolised (>60%) by hepatic oxidation/glucuronidation — in severe hepatic impairment (Child-Pugh C cirrhosis), REDUCE TOTAL DAILY DOSE BY 50% (e.g., 400 mg every 12h instead of TDS) to prevent cerebellar ataxia and encephalopathy.
7. Contraindications, Precautions & High-Risk Warnings
- Contraindicated in the first trimester of pregnancy (for high-dose trichomoniasis regimens) and severe active CNS organic disease. Caution in hepatic encephalopathy/cirrhosis and blood dyscrasias.
Key Clinical Precautions: Renal: Parent drug unchanged in mild-moderate CKD, but active hydroxy-metabolites accumulate in CrCl <10 mL/min or haemodialysis (supplement post-dialysis or reduce by 50% in prolonged courses). Hepatic: Metabolised (>60%) by hepatic oxidation/glucuronidation — in severe hepatic impairment (Child-Pugh C cirrhosis), REDUCE TOTAL DAILY DOSE BY 50% (e.g., 400 mg every 12h instead of TDS) to prevent cerebellar ataxia and encephalopathy.
8. Adverse Effects Profile
- Strong unpleasant metallic / bitter taste in the mouth (dysgeusia), furry tongue/glossitis, nausea, anorexia, epigastric distress, harmless dark reddish-brown or cola-coloured urine (due to water-soluble azo pigment metabolite).
- Severe Disulfiram-Like Reaction with Alcohol, Peripheral Sensory Neuropathy (numbness/paresthesia of hands and feet with prolonged or repeated courses), Metronidazole-Induced Encephalopathy / Cerebellar Toxicity (ataxia, dysarthria, confusion, seizures—reversible on stopping), leukopenia, pancreatitis.
9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions
- Warfarin / Acenocoumarol (potent CYP2C9 inhibition -> markedly elevates INR and major bleeding risk; avoid or reduce coumarin by 30–50% and check INR within 3–5 days)
- Lithium (reduces renal lithium clearance -> acute lithium nephro/neurotoxicity)
- Alcohol & Propylene-glycol liquid formulations (classic disulfiram-like flushing, throbbing headache, vomiting, tachycardia, hypotension; while controlled mechanistic studies debate aldehyde dehydrogenase inhibition, severe clinical reactions occur — enforce strict alcohol abstinence during therapy and for 48–72h post-course)
- Phenytoin/Fluorouracil (reduced clearance)
10. Clinical Monitoring, Patient Counselling & Storage
Clinical & Laboratory Monitoring: Monitor clinical parameters per parent class monograph [8.11].
Pharmacist Patient Counselling Points:
- Patient Counselling Checklist: Reassure the patient about two expected effects so they do not stop the course prematurely: (1) A metallic/iron-like taste in the mouth is normal and disappears once the course finishes (sucking sugar-free mints or taking after meals helps); (2) Urine may turn dark brown or reddish-tea coloured—this is a harmless colour from the broken-down tablet, NOT blood or liver damage! Enforce the strict 72-hour post-course alcohol ban.
- Meal & Clock Timing Instruction: Take WITH or immediately AFTER food with a full glass of water (significantly reduces nausea, epigastric cramping, and metallic taste). (Three times daily after breakfast, lunch, and dinner (every 8 hours).)
- Missed Dose Protocol: Take with food as soon as remembered unless within 3 hours of next dose; never double.
- Geriatric Dispensing Pearl: Always check if an elderly CGHS patient is on Warfarin/Acitrom before dispensing Flagyl/Metrogyl (triggers severe GI/intracranial bleeds within days!), and reduce dose by 50% in patients with liver cirrhosis.
Storage, Stability & Dispensing Safeguards: Store below 25°C–30°C in original moisture- and light-resistant packaging out of reach of children. Available forms: Oral Film-Coated Tablets: 200 mg, 400 mg; Extended-Release: 600 mg ER; Oral Suspension (Metronidazole Benzoate—tasteless): 200 mg/5 mL; IV Infusion: 500 mg/100 mL; Topical/Dental Gel: 1%–2% w/w
11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)
12. Authoritative References, Regulatory Sources & Editorial Disclaimer
Primary Compendial & Guideline Reference: Indian Pharmacopoeia (IP 2022) • NFI • CDSCO
Official Verification Portals: Indian Pharmacopoeia Commission (IPC) & National Formulary of India (NFI) • Central Drugs Standard Control Organization (CDSCO) • Ministry of Health & Family Welfare — NLEM 2022 • NCBI Bookshelf / StatPearls Pharmacology Reference • DailyMed (US FDA Official Prescribing Reference)
Last Medically & Pharmaceutically Reviewed: 2026-11-10 • Verification Status: VERIFIED_EDUCATIONAL_CONTENT
Educational & Clinical Disclaimer: This reference profile is published solely for pharmacy education, academic study, and professional clinical reference. It does not substitute for patient-specific clinical judgement, qualified specialist oncology/medical supervision, or official CDSCO/IP prescribing information. Never self-medicate with prescription, Schedule H/H1/X, NDPS, or oncology medicines.
13. Related Reference Monographs, Educational Guides & Visual Concept
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