Dosage
Amebiasis (acute dysentery): Oral: Immediate-release tablets and capsules:
750 mg every 8 hours for 5 to 10 days
750 mg every 8 hours for 5 to 10 days
Amebic liver abscess: Oral:
Immediate-release tablets: 500 to 750 mg every 8 hours for 5 to 10 days
Capsules: 750 mg every 8 hours for 5 to 10 days
Bacterial vaginosis or vaginitis due to Gardnerella, Mobiluncus: Oral:
Tablet:
Immediate release (off-label use): 500 mg twice daily for 7 days
Extended release: 750 mg once daily for 7 days
Tablet:
Immediate release (off-label use): 500 mg twice daily for 7 days
Extended release: 750 mg once daily for 7 days
Intra-abdominal infection:
Manufacturer’s labeling: Oral (immediate release), IV: 500 mg every 6 hours (maximum: 4 g/day); Note: Initial: 1 g IV loading dose may be administered
Alternate dosing:
Acute diverticulitis, outpatient treatment: Oral (immediate release): 500 mg every 6 to 8 hours; use in combination with a fluoroquinolone (eg, ciprofloxacin) or sulfamethoxazole and trimethoprim (Jacobs 2007)
Complicated, community-acquired, mild to moderate (in combination with cephalosporin or fluoroquinolone): IV: 500 mg every 8 to 12 hours or 1.5 g every 24 hours for 4 to 7 days (provided source controlled) (Solomkin 2010)
Pelvic inflammatory disease (off-label dose): Oral (immediate release):
Mild to moderately severe: 500 mg twice daily for 14 days (may be added to a combination of a third-generation parenteral cephalosporin and doxycycline) (CDC [Workowski 2015])
With tubo-ovarian abscess: 500 mg twice daily to complete at least 14 days of therapy (in combination with doxycycline following a parenteral therapy regimen)
Trichomoniasis (index case and sex partner):
Oral:
Oral:
Immediate-release tablets:
Manufacturer’s labeling: 250 mg every 8 hours for 7 days or 1 g twice daily for 2 doses (on same day) or 2 g as a single dose
Alternate dosing: 2 g as a single dose (preferred regimen) or 500 mg twice daily for 7 days (off-label dose) (CDC [Workowski 2015])
Capsules: 375 mg twice daily for 7 days
Trichomoniasis in HIV-infected women (off-label dose): Oral (immediate release): 500 mg twice daily for 7 days (CDC [Workowski 2015])
Trichomoniasis, persistent or recurrent (ie, treatment failure of nitroimidazole [eg metronidazole] single-dose therapy) (index case; treatment of sex partner; off-label dose): Oral (immediate release): 500 mg twice daily for 7 days. If this regimen also fails, consider 2 g once daily for 7 days (CDC [Workowski 2015])
Balantidiasis (off-label use): IV, Oral (immediate release): 750 mg 3 times daily for ≥5 days (Anagyrou 2003; Schuster 2008)
Bite wounds (animal/human) (off-label use) (IDSA [Stevens 2014]): Note: Use in combination with a second- or third-generation cephalosporin, levofloxacin, or sulfamethoxazole/trimethoprim for animal bites, or in combination with ciprofloxacin or levofloxacin for human bites.
Oral: 250 to 500 mg 3 times daily
IV: 500 mg every 8 hours
Clostridium difficile-associated diarrhea (CDAD) (off-label use): Note: Recent guideline recommends converting to oral vancomycin therapy if the patient does not show a clear clinical response after 5 to 7 days of metronidazole therapy (Surawicz 2013)
Mild to moderate infection: Oral (immediate release): 500 mg 3 times daily for 10 to 14 days (Cohen 2010; Surawicz 2013)
Severe complicated infection (no abdominal distention): IV: 500 mg 3 times daily with oral vancomycin for 10 to 14 days (Surawicz 2013)
Severe complicated infection (with ileus, toxic colitis, and/or abdominal distention): IV: 500 mg 3 times daily with oral and rectal vancomycin for 10 to 14 days (Surawicz 2013)
Crohn disease, mild to moderate (off-label use): Oral (immediate release): 10 to 20 mg/kg/day (Lichtenstein 2009) or 500 mg twice daily (in combination with ciprofloxacin) (Steinhart 2002).
Dientamoeba fragilis infections (off-label use): Oral (immediate release): 500 to 750 mg 3 times daily for 10 days (CDC 2012)
Giardiasis (off-label use): Oral (immediate release): 250 to 500 mg 3 times daily for 5 to 10 days (Granados 2012)
Helicobacter pylori eradication (off-label use): Oral (immediate release):
Triple therapy: Metronidazole 500 mg twice daily for 10 to 14 days, in combination with clarithromycin and a proton pump inhibitor (Chey 2007)
Quadruple therapy: Metronidazole 250 mg 4 times daily for 10 to 14 days, in combination with bismuth subsalicylate, a tetracycline, and either ranitidine or a proton pump inhibitor (Chey 2007)
Periodontitis (associated with aggressive disease; off-label use): Oral (immediate release): 250 mg every 8 hours in combination with amoxicillin for 10 days; used in addition to scaling, root planing and pocket irrigation (Silva-Senem 2013)
Pouchitis (post ileal pouch-anal anastomosis, acute treatment; off-label use): Oral (immediate release): 400 to 500 mg three times daily for 7 days (Holubar 2010; Wall 2011)
Prophylaxis against sexually-transmitted diseases following sexual assault (off-label use): Oral (immediate release): 2 g as a single dose in combination with ceftriaxone and azithromycin (CDC [Workowski 2015])
Skin and soft tissue necrotizing infections (off-label use): IV: 500 mg every 6 hours, in combination with cefotaxime or ceftriaxone for empiric therapy of polymicrobial infections. Continue until further debridement is not necessary, patient has clinically improved, and patient is afebrile for 48 to 72 hours (IDSA [Stevens 2014]).
Surgical prophylaxis:
Manufacturer’s labeling: IV: 15 mg/kg 1 hour prior to surgical incision; followed by 7.5 mg/kg 6 and 12 hours after initial dose
Alternate dosing:
IV: 500 mg within 60 minutes prior to surgical incision in combination with other antibiotics (Bratzler 2013). Note: Considered a recommended agent for select procedures other than colorectal surgery (off-label use) (Bratzler 2013).
Oral (for colorectal surgical prophylaxis only; immediate release; off-label use): 1 g every 3 to 4 hours for 3 doses, starting after mechanical bowel preparation the afternoon and evening before the procedure with or without additional oral antibiotics and with an appropriate IV antibiotic prophylaxis regimen (Bratzler 2013).
Surgical site infections (intestinal or GU tract; axilla or perineum) (off-label use): IV: 500 mg every 8 hours; in combination with ceftriaxone, ciprofloxacin, or levofloxacin (IDSA [Stevens 2014]).
Tetanus (Clostridium tetani infection; off-label use): Oral (immediate release): 500 mg every 6 hours for 7 to 10 days in combination with supportive therapy (Ahmadsyah, 1985)
Urethritis, nongonococcal (recurrent or persistent urethritis in men who have sex with women and who live in regions where T. vaginalis is prevalent; off-label use):Oral (immediate release): 2 g as a single dose. Note: Compliance with initial regimen and lack of re-exposure to an untreated sex partner should be excluded prior to use (CDC [Workowski 2015])
