Ornidazole

# Ornidazole ## Overview - **Classification**: Nitroimidazole antibiotic, antiprotozoal. - **Mechanism**: A prodrug that is reduced intracellularly by anaerobic organisms, forming reactive nitro-radicals that damage bacterial and protozoal DNA, leading to cell death. ## Primary Indications 1. **Amebiasis** - Intestinal and hepatic forms of amoebic infection. 2. **Giardiasis** - Infection caused by *Giardia intestinalis*. 3. **Trichomoniasis** - Sexually transmitted infection caused by *Trichomonas vaginalis*. 4. **Anaerobic Bacterial Infections** - Treatment and prophylaxis for susceptible anaerobic bacteria. 5. **H. pylori Eradication** - As part of multi-drug regimens. ## Adult Dosing ### Standard Dosing **Amebiasis (Intestinal)** - **Dose**: **500 mg** - **Frequency**: Every 12 hours - **Route**: Oral - **Duration**: 5-10 days **Amebiasis (Hepatic)** - **Dose**: **500 mg** - **Frequency**: Every 12 hours - **Route**: Oral/IV - **Duration**: 5-10 days (often followed by luminal amebicide) **Giardiasis** - **Dose**: **1.5 g** - **Frequency**: Once daily - **Route**: Oral - **Duration**: 1-2 days (or **500 mg** BID for 5-7 days) **Trichomoniasis** - **Dose**: **1.5 g** - **Frequency**: Single dose - **Route**: Oral - **Duration**: 1 day (or **500 mg** BID for 5 days) **Anaerobic Infections (Treatment)** - **Dose**: Initial **1 g** (loading), then **500 mg** - **Frequency**: Every 12 hours - **Route**: IV/Oral - **Duration**: 5-10 days, or until clinical improvement **Surgical Prophylaxis (Anaerobic)** - **Dose**: **1 g** - **Frequency**: Single dose - **Route**: IV - **Special Considerations**: Administer 30 minutes before surgery. ### Dose Adjustments - **Renal Impairment**: No dose adjustment generally needed for single doses or short courses. For prolonged therapy, consider reducing frequency to Q24h for CrCl < 10 mL/min. - **Hepatic Impairment**: Reduce dose by **50%** in severe hepatic impairment (Child-Pugh C). - **Elderly Patients**: No specific adjustment, but monitor for adverse effects due to potential decreased organ function. ## Pediatric Dosing ### Neonates (0-28 days) - **Use**: Generally **not recommended** due to immature metabolic pathways. - **Special Notes**: Use only if essential and under strict medical supervision; no standard dosing. ### Infants (1-12 months) - **Indication**: Amebiasis, Giardiasis. - **Dose**: **20-40 mg/kg/day** - **Frequency**: Divided every 12 hours - **Maximum**: **500 mg** per dose - **Special Notes**: Oral suspension preferred. ### Children (1-12 years) - **Indication**: Amebiasis, Giardiasis. - **Dose**: **20-40 mg/kg/day** - **Frequency**: Divided every 12 hours - **Maximum**: **1.5 g/day** (or adult dose for single-dose regimens) - **Special Notes**: Oral suspension or tablets (if age-appropriate for swallowing). ### Adolescents (13-18 years) - **Dose**: Use adult dosing regimens. - **Maximum**: Adult maximum doses apply. - **Special Notes**: Consider lower end of adult dose range initially. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to ornidazole or other nitroimidazole derivatives. - **Absolute**: First trimester of pregnancy (relative for others). - **Relative**: Patients with CNS disorders (e.g., epilepsy, multiple sclerosis). - **Relative**: History of blood dyscrasias. ### Common Adverse Effects - **Very Common (>10%)**: Nausea, metallic taste, headache. - **Common (1-10%)**: Vomiting, dizziness, drowsiness, abdominal pain, diarrhea. - **Serious but Rare**: Peripheral neuropathy (especially with prolonged use), seizures, leukopenia. ### Key Drug Interactions - **Warfarin**: Enhances anticoagulant effect. Monitor INR closely, adjust warfarin dose. - **Alcohol**: Potential for disulfiram-like reaction (abdominal cramps, flushing); advise avoidance during and for 48h after treatment. - **Lithium**: May increase lithium levels. Monitor lithium levels, adjust dose if needed. ## Monitoring & Follow-up - **Before Treatment**: Baseline neurological assessment (if history of CNS issues). - **During Treatment**: Monitor for CNS side effects (e.g., neuropathy, seizures). - **During Treatment**: Complete blood count (CBC) if treatment prolonged or blood dyscrasias suspected. - **Clinical Signs**: Watch for persistent GI upset, dizziness, numbness/tingling in extremities. ## Clinical Pearls - 💡 **Take with food**: To reduce gastrointestinal upset and metallic taste. - 💡 **Avoid alcohol**: Advise patients to avoid alcohol during treatment and for at least 48 hours after. - 💡 **Complete full course**: Emphasize completing the entire prescribed course, even if symptoms improve, to prevent resistance and relapse. - 💡 **Metallic taste**: Reassure patients about transient metallic taste, a common side effect. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.