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## Metrogyl (Metronidazole)
### Overview
Metronidazole is an antibacterial and antiprotozoal agent effective against anaerobic bacteria and certain protozoa.
### Primary Indications
* **Bacterial Vaginosis:** Treatment of vaginal infections.
* **Trichomoniasis:** Treatment of sexually transmitted infection.
* **Giardiasis:** Treatment of intestinal infection.
* **Amebiasis:** Treatment of intestinal and extraintestinal infections.
* **Anaerobic Bacterial Infections:** Treatment of infections caused by susceptible anaerobic organisms (e.g., intra-abdominal infections, gynecologic infections, skin and soft tissue infections, bone and joint infections, CNS infections, lower respiratory tract infections, endocarditis).
* **Pseudomembranous Colitis (C. difficile infection):** Alternative agent.
* **Surgical Prophylaxis:** Prevention of anaerobic infection in specific surgical procedures.
### Adult Dosing
* **Bacterial Vaginosis:** 500 mg orally twice daily for 7 days, OR 2 g orally as a single dose, OR 0.75% vaginal gel applied once intravaginally at bedtime for 5 days.
* **Trichomoniasis:** 2 g orally as a single dose, OR 250 mg orally three times daily for 7 days, OR 375 mg orally twice daily for 7 days.
* **Giardiasis:** 250 mg orally three times daily for 5 days, OR 500 mg orally twice daily for 5-7 days.
* **Amebiasis:**
* **Intestinal:** 500-750 mg orally three times daily for 5-10 days.
* **Extra-intestinal (e.g., liver abscess):** 500-750 mg orally three times daily for 5-10 days.
* **Anaerobic Bacterial Infections:** 500 mg IV every 8 hours, OR 250-750 mg orally every 6-8 hours. Typical duration is 7-14 days, depending on infection.
* **Pseudomembranous Colitis:** 500 mg orally three times daily for 10-14 days.
* **Surgical Prophylaxis:** 1 g IV 30-60 minutes before surgery, then 500 mg orally or IV every 8 hours for up to 24 hours post-operatively.
### Pediatric Dosing
Dosing varies significantly by indication and weight. Consult specific pediatric guidelines.
* **Giardiasis:** 15 mg/kg/day orally in 3 divided doses, not to exceed 250 mg per dose, for 5-7 days.
* **Amebiasis:** 35-50 mg/kg/day orally or IV in 3 divided doses for 5-10 days.
* **Anaerobic Bacterial Infections:** 7.5 mg/kg/dose IV every 8 hours, OR 15 mg/kg/dose IV every 12 hours for anaerobic infections. Do not exceed 4 g/day.
### Dose Adjustments
* **Renal Impairment:** No specific dose adjustment required for the parent drug, but metabolites are renally eliminated. Consider monitoring if impairment is severe.
* **Hepatic Impairment:** Reduce daily dose by 30-50% in severe hepatic disease.
### Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* First trimester of pregnancy (though benefits may outweigh risks in severe infections).
### Adverse Effects
* **Common:** Nausea, metallic taste, anorexia, abdominal discomfort, diarrhea, headache, dizziness.
* **Serious:** Peripheral neuropathy, seizures, encephalopathy, pancreatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis, severe allergic reactions, disulfiram-like reaction with alcohol.
### Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, tachycardia, shortness of breath). Avoid alcohol during and for at least 3 days after treatment.
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely and adjust warfarin dose as needed.
* **Lithium:** Metronidazole may increase lithium levels, potentially leading to toxicity. Monitor lithium levels.
* **Phenobarbital, Phenytoin:** May increase metronidazole metabolism, reducing efficacy.
* **Cyclosporine:** May increase cyclosporine levels. Monitor cyclosporine levels.
### Monitoring
* Signs and symptoms of infection.
* Gastrointestinal tolerance.
* Neurological status (especially with prolonged therapy or high doses).
* Peripheral neuropathy symptoms (numbness, tingling).
* Renal and hepatic function (especially in patients with impaired function).
* INR if co-administered with warfarin.
### Clinical Pearls
* Administer oral metronidazole with or without food.
* IV metronidazole can be administered alone or mixed with IV fluids.
* Urine may turn a reddish-brown color; this is harmless.
* Instruct patients to avoid alcohol during and for at least 72 hours after therapy.
* For trichomoniasis, treat sexual partners concurrently.
* IV formulation is preferred for severe infections or when oral administration is not feasible.
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*This information is intended for healthcare professionals. Please consult the current prescribing information for complete details and to verify information before making clinical decisions.*
