Metronidazole 400mg Tablets Dosing Schedule
For metronidazole 400mg tablets, the recommended dosing schedule is 400mg three times daily for most indications, with specific duration depending on the condition being treated.
Dosing Schedules by Indication
Trichomoniasis
- First-line regimen: 400mg three times daily for 7 days 1, 2
- Alternative regimen: 2g (5 tablets of 400mg) as a single dose 1, 2
- The 7-day regimen has shown higher cure rates (97.3%) compared to single-dose treatment (93.8%) 3
Bacterial Vaginosis
- 400mg three times daily for 5-7 days 4
Clostridium difficile Infection (CDI)
- 400mg three times daily for 10 days (equivalent to 500mg three times daily) 5
- Note: Vancomycin or fidaxomicin is now preferred over metronidazole for initial CDI episodes 5
- For fulminant CDI with ileus: IV metronidazole 500mg every 8 hours in combination with oral/rectal vancomycin 5
Amebiasis
- Intestinal amebiasis (acute amebic dysentery): 400mg three times daily for 5-10 days 2
- Amebic liver abscess: 400mg three times daily for 5-10 days 2
Anaerobic Bacterial Infections
- 400mg every 8 hours for 7-10 days 2
- Note: Infections of bone, joint, lower respiratory tract, and endocardium may require longer treatment 2
Special Considerations
Pregnancy
- Metronidazole is contraindicated during the first trimester 1, 2
- For trichomoniasis after first trimester, the 7-day regimen is preferred over single-dose treatment 1
Elderly Patients
- Pharmacokinetics may be altered; monitoring of serum levels may be necessary to adjust dosage 2
Hepatic Impairment
- Lower doses should be administered cautiously in patients with severe hepatic disease due to slower metabolism and accumulation of metronidazole and its metabolites 2
Renal Impairment
- No specific dose reduction needed in anuric patients as metabolites can be removed by dialysis 2
Important Precautions
- Patients should avoid alcohol during treatment and for 24-48 hours afterward to prevent disulfiram-like reactions 1
- For recurrent infections requiring repeated courses, allow 4-6 weeks between courses 2
- Avoid prolonged courses due to risk of cumulative and potentially irreversible neurotoxicity 5
- Common side effects include nausea (23%), headache (7%), and vomiting (4%) 3
Treatment Follow-up
- For trichomoniasis, consider retesting 3 months after treatment 1
- For C. difficile, consider extending treatment to 14 days if response is delayed 5
While twice-daily dosing (every 12 hours) has been studied for hospitalized patients with anaerobic infections with comparable outcomes to every 8-hour dosing 6, the standard recommended regimen for 400mg tablets remains three times daily for most indications based on current guidelines.