Ornidazole

# Ornidazole ## Overview - **Classification**: Nitroimidazole derivative, antiprotozoal, antibacterial. - **Mechanism**: Enters microbial cells, reduced to reactive nitro-radicals. These radicals damage microbial DNA and macromolecules, leading to cell death. ## Primary Indications 1. **Amoebiasis**: Intestinal and hepatic forms caused by *Entamoeba histolytica*. 2. **Giardiasis**: Intestinal infection caused by *Giardia lamblia*. 3. **Trichomoniasis**: Urogenital infections caused by *Trichomonas vaginalis*. 4. **Anaerobic Bacterial Infections**: Treatment and prophylaxis (e.g., in surgery). ## Adult Dosing ### Standard Dosing **Amoebiasis (Intestinal or Hepatic)** - **Dose**: **500 mg** - **Frequency**: Twice daily - **Route**: Oral - **Duration**: **5-10 days** (or **1000 mg** once daily for **5 days**) **Giardiasis** - **Dose**: **1000-1500 mg** - **Frequency**: Once daily - **Route**: Oral - **Duration**: **1-2 days** (single dose of **1500 mg** common) **Trichomoniasis** - **Dose**: **1500 mg** - **Frequency**: Single dose OR **500 mg** twice daily - **Route**: Oral - **Duration**: **1 day** (single dose) or **5-7 days** **Anaerobic Infections (Treatment)** - **Dose**: Initial **500-1000 mg** IV loading, then **500 mg** - **Frequency**: Initial once, then every 12 hours - **Route**: IV, then switch to oral once stable - **Duration**: Usually **5-10 days** **Anaerobic Infections (Surgical Prophylaxis)** - **Dose**: **1000 mg** - **Frequency**: Single dose - **Route**: IV or Oral - **Duration**: Administer **30-60 minutes** prior to surgery ### Dose Adjustments - **Renal Impairment**: No dose adjustment typically needed for CrCl > 10 mL/min. Consider 50% dose reduction for severe renal impairment or hemodialysis. - **Hepatic Impairment**: Dose reduction may be necessary in severe hepatic dysfunction. Monitor for prolonged half-life and adverse effects. - **Elderly Patients**: No specific adjustment; use caution due to potential age-related decline in organ function. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: Data limited; generally **avoid** due to immature metabolic pathways. - **Frequency**: N/A - **Maximum**: N/A - **Special Notes**: Use only if essential and benefits outweigh risks. Consult pediatric infectious disease. ### Infants (1-12 months) - **Dose**: **25-40 mg/kg/day** - **Frequency**: Once daily or divided twice daily - **Maximum**: **1000 mg/day** (consider lower for prolonged courses) - **Special Notes**: Liquid formulations are preferred for ease of administration. ### Children (1-12 years) - **Dose**: **25-40 mg/kg/day** - **Frequency**: Once daily (e.g., for single-dose Giardiasis) or divided twice daily. - **Maximum**: **1000 mg/day** (up to **1500 mg** for single dose in Giardiasis). - **Special Notes**: Tablets can be crushed, or liquid formulation used based on patient ability. ### Adolescents (13-18 years) - **Dose**: Use adult dosing guidelines, typically **500 mg** twice daily or **1000-1500 mg** once daily. - **Maximum**: **1500 mg/day**. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to ornidazole or other nitroimidazole derivatives. - **Absolute**: First trimester of pregnancy (relative in later trimesters; use only if clearly needed). - **Absolute**: Organic neurological disorders (e.g., epilepsy, multiple sclerosis). ### Common Adverse Effects - **Common (1-10%)**: Nausea, vomiting, abdominal discomfort, metallic taste, headache, dizziness, fatigue. - **Less Common (0.1-1%)**: Vertigo, somnolence, tremor, confusion, skin rash. - **Serious but Rare**: Seizures, peripheral neuropathy (especially with prolonged use), blood dyscrasias, hepatic dysfunction, severe allergic reactions. ### Key Drug Interactions - **Oral Anticoagulants (e.g., Warfarin)**: May potentiate anticoagulant effect, increasing bleeding risk. **Monitor INR closely**; adjust anticoagulant dose. - **Ethanol (Alcohol)**: Disulfiram-like reaction (flushing, abdominal cramps) is possible but less common than with metronidazole. **Advise avoiding alcohol** during and for 48 hours after treatment. - **Lithium**: May increase lithium levels, leading to toxicity. **Monitor lithium levels**. - **Vecuronium Bromide**: May prolong neuromuscular blocking effects. Monitor for prolonged paralysis. ## Monitoring & Follow-up - **Before Treatment**: Assess liver function in patients with pre-existing hepatic impairment. Assess baseline neurological status. - **During Treatment**: Monitor for neurological symptoms (e.g., numbness, tingling, seizures), especially with prolonged courses. - **Clinical Signs**: Report persistent gastrointestinal upset, unusual fatigue, jaundice, or any new neurological symptoms immediately. ## Clinical Pearls - 💡 **Tip 1**: Administer with food to minimize gastrointestinal upset. - 💡 **Tip 2**: For single-dose regimens (e.g., Giardiasis), ensure patient compliance for efficacy. - 💡 **Tip 3**: Counsel patients to strictly avoid alcohol during therapy and for at least 48 hours after the last dose. - 💡 **Tip 4**: Be vigilant for signs of peripheral neuropathy (e.g., tingling, numbness) with prolonged use. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.