From the Guidelines
The recommended dose of metronidazole is 500 mg orally twice a day for 7 days, as indicated for bacterial vaginosis. This dose is supported by the most recent and highest quality study available, which prioritizes morbidity, mortality, and quality of life as the outcome 1.
Indications and Dosage
- For bacterial infections, the typical dose is 500 mg orally three times daily for 7-10 days.
- For trichomoniasis, a single 2-gram dose is effective, or 500 mg twice daily for 7 days.
- For bacterial vaginosis, 500 mg twice daily for 7 days or 750 mg once daily for 7 days is recommended.
- For Clostridium difficile infection, 500 mg orally three times daily for 10-14 days is standard.
- For giardiasis, 250 mg three times daily for 5-7 days is used.
- For amoebiasis, 500-750 mg three times daily for 7-10 days is recommended.
Important Considerations
- Dosing should be adjusted for patients with severe hepatic impairment.
- Common side effects include metallic taste, nausea, and disulfiram-like reaction with alcohol.
- Metronidazole works by disrupting bacterial DNA, making it effective against anaerobic bacteria and certain parasites.
- Always take the full course as prescribed, even if symptoms improve before completion, as indicated by studies such as 1, 1, and 1.
From the FDA Drug Label
DOSAGE AND ADMINISTRATION In elderly patients, the pharmacokinetics of metronidazole may be altered, and, therefore, monitoring of serum levels may be necessary to adjust the metronidazole dosage accordingly. Trichomoniasis In the Female One-day treatment— two grams of metronidazole tablets, given either as a single dose or in two divided doses of one gram each given in the same day Seven-day course of treatment— 250 mg three times daily for seven consecutive days. Amebiasis Adults For acute intestinal amebiasis (acute amebic dysentery): 750 mg orally three times daily for 5 to 10 days. For amebic liver abscess: 500 mg or 750 mg orally three times daily for 5 to 10 days. Anaerobic Bacterial Infections In the treatment of most serious anaerobic infections, the intravenous form of metronidazole is usually administered initially. The usual adult oral dosage is 7. 5 mg/kg every six hours (approx. 500 mg for a 70 kg adult).
The metronidazole dose varies depending on the condition being treated.
- For trichomoniasis, the dose is either 2 grams as a single dose or 250 mg three times daily for 7 consecutive days.
- For amebiasis, the dose is 750 mg orally three times daily for 5 to 10 days.
- For anaerobic bacterial infections, the usual adult oral dosage is 7.5 mg/kg every six hours (approximately 500 mg for a 70 kg adult) 2.
From the Research
Metronidazole Dose Information
- The recommended dose of metronidazole is 500 mg three times per day 3.
- An adaptation of the dose is necessary in cases of renal insufficiency 3.
- Metronidazole is well tolerated when administered in dosages of less than 2 g per day 3.
- A single-dose of 2 g of metronidazole is the first-line treatment for trichomoniasis 4.
- A 7-day dose of 500 mg of metronidazole twice daily has been shown to be more effective than a single dose for the treatment of trichomoniasis in women 4, 5.
- For the treatment of bacterial vaginosis, oral metronidazole (500 mg twice daily for 7 days) is the preferred treatment 6.
- Other effective treatment regimens for bacterial vaginosis include single-dose metronidazole (2 g orally), 2% clindamycin vaginal cream, 0.75% metronidazole vaginal gel, and oral clindamycin 6.
Special Considerations
- Metronidazole has limited plasma protein binding but can reach favorable tissue distribution, including the central nervous system and placenta 3.
- The drug is extensively metabolized by the liver to form 5 oxidative metabolites 3.
- The majority of the drug and metabolites are excreted in urine and feces 3.
- The half-life of metronidazole is 6 to 10 hours 3.
- Drug interactions with alcohol, warfarin, and phenytoin have been reported 3.