Ornidazole

• Protozoal Infections:
• Treatment of amoebiasis (intestinal and hepatic amoebiasis).
• Giardiasis (intestinal giardiasis).
• Trichomoniasis (urogenital and vaginal).
• Anaerobic Bacterial Infections:
• Intra-abdominal infections.
• Gynecological infections including pelvic inflammatory disease.
• Anaerobic infections of skin, soft tissues, bone, and joints.
• Dental Infections:
• Periodontitis and gingivitis associated with anaerobic bacteria.
• Off-label:
• Helicobacter pylori eradication in combination with other antibiotics.
• Post-surgical infections involving anaerobic bacteria.

• Route: Oral, intravenous, or intramuscular.
• Adults:
• Oral: 500 mg twice daily for 5–10 days depending on infection type.
• IV/IM: 500 mg once or twice daily as needed for severe infections.
• Pediatrics:
• Generally 15–30 mg/kg/day divided into two doses (not exceeding adult doses).
• Elderly:
• No specific dosage adjustment; use cautiously considering renal/hepatic function.
• Renal/Hepatic Impairment:
• Dose adjustment recommended in severe hepatic or renal impairment.
• Duration:
• Varies by infection; generally 5 to 10 days, longer in complicated infections.

Ornidazole is a nitroimidazole derivative that exhibits antimicrobial activity against anaerobic bacteria and protozoa. It penetrates microbial cells and undergoes reductive activation of its nitro group by intracellular electron transport proteins. This activation generates cytotoxic free radicals and reactive metabolites that damage DNA and other critical biomolecules, leading to strand breaks, inhibition of nucleic acid synthesis, and ultimately microbial cell death.

• Absorption: Rapid and nearly complete oral absorption (>90%).
• Peak Plasma Concentration: Achieved within 2–3 hours post oral administration.
• Bioavailability: Approximately 90%.
• Distribution: Widely distributed, including cerebrospinal fluid, bile, and vaginal secretions.
• Metabolism: Primarily hepatic metabolism via reduction and conjugation pathways.
• Half-life: Approximately 12–14 hours, allowing twice-daily dosing.
• Elimination: Excreted mainly via the urine (60–80%) as metabolites and unchanged drug.

• Pregnancy:
• Category B (FDA): No adequate controlled studies in pregnant women, but animal studies have shown no harm. Use only if clearly needed.
• Lactation:
• Excreted in breast milk in small amounts; caution advised when administered to breastfeeding mothers.

• Nitroimidazole antimicrobial agent.

• Known hypersensitivity to ornidazole or other nitroimidazoles.
• First trimester of pregnancy (relative contraindication).
• Severe hepatic impairment.
• Concomitant use with disulfiram or alcohol (due to disulfiram-like reaction).

• Avoid alcohol consumption during treatment and for at least 48 hours after completion to prevent disulfiram-like reactions.
• Monitor for signs of peripheral neuropathy, especially with prolonged use.
• Use with caution in patients with history of blood dyscrasias or neurological disorders.
• Caution in patients with hepatic or renal impairment; dose adjustment may be required.
• Monitor for central nervous system adverse effects such as seizures or encephalopathy.

• Common:
• Gastrointestinal: Nausea, vomiting, abdominal discomfort, metallic taste.
• Central nervous system: Headache, dizziness.
• Serious (Rare):
• Peripheral neuropathy, seizures, encephalopathy.
• Hypersensitivity reactions including rash, urticaria.
• Other:
• Transient leukopenia, thrombocytopenia.
• Dark urine due to drug metabolites (harmless).

• Alcohol: May cause disulfiram-like reaction (flushing, nausea, vomiting, tachycardia). Avoid concomitant use.
• Anticoagulants (e.g., warfarin): May enhance anticoagulant effect; monitor INR closely.
• Phenytoin and phenobarbital: May reduce ornidazole plasma levels via enzyme induction.
• Cyclosporine: Potential increased risk of neurotoxicity.
• Lithium: May increase lithium toxicity risk.

• No significant recent changes in approved indications.
• Continued emphasis on avoiding alcohol during and shortly after therapy.
• Recommendations for monitoring neurological symptoms during prolonged therapy.
• WHO includes nitroimidazoles like ornidazole on essential medicines lists for protozoal and anaerobic infections in some regions.

• Store at 20°C to 25°C (68°F to 77°F).
• Protect from moisture and light.
• Keep container tightly closed.
• Avoid freezing.