Metronidazole has been shown to be carcinogenic in mice and rats. Unnecessary use of the drug should be avoided. Its use should be reserved for the conditions for which this drug is indicated.
Amebiasis, intestinal (acute dysentery) or extraintestinal (liver abscess): Oral: 500 to 750 mg every 8 hours for 7 to 10 days followed by an intraluminal agent (eg, paromomycin) (Drugs for Parasitic Infections 2013; Leder 2022a; Leder 2018b).
Balantidiasis (alternative agent) (off-label use): Oral: 750 mg 3 times daily for 5 days (CDC 2013; Drugs for Parasitic Infections 2013; Weller 2021).
Bite wound infection, prophylaxis or treatment, animal or human bite (alternative agent) (off-label use): Oral, IV: 500 mg every 8 hours (Baddour 2021a; Baddour 2021b; IDSA [Stevens 2014]). Duration is 3 to 5 days for prophylaxis; duration of treatment for established infection is typically 5 to 14 days and varies based on clinical response and patient-specific factors (Baddour 2021a; Baddour 2021b). Note: For animal bites, use in combination with an appropriate agent for Pasteurella multocida. For human bites, use in combination with an appropriate agent for Eikenella corrodens (IDSA [Stevens 2014]).
Clostridioides difficile infection, treatment (off-label use):
Note: Criteria for disease severity is based on expert opinion and should not replace clinical judgment (ACG [Kelly 2021]; IDSA/SHEA [Johnson 2021]).
Nonsevere (ie, WBC ≤15,000 cells/mm3 and serum creatinine <1.5 mg/dL), initial episode (alternative agent if oral vancomycin or fidaxomicin unavailable or contraindicated): Oral: 500 mg 3 times daily for 10 to 14 days (IDSA/SHEA [Johnson 2021]).
Fulminant infection (ie, ileus, megacolon, and/or hypotension/shock): IV: 500 mg every 8 hours in combination with oral and/or rectal vancomycin for 10 days; may be extended up to 14 days if patient has improved but has not had symptom resolution (ACG [Kelly 2021]; IDSA/SHEA [Johnson 2021]; Kelly 2021).
Crohn disease, (off-label use):
Management after surgical resection:
Monotherapy: Oral: 20 mg/kg/day (in 3 divided doses) or 1 to 2 g/day in divided doses for 3 months (ACG [Lichtenstein 2018]; Rutgeerts 1995); begin as soon as oral intake is resumed after surgery (Rutgeerts 1995).
Combination therapy: Oral: 250 mg 3 times daily (D’Haens 2008; Lopez-Sanromán 2017) or 1 to 2 g/day in divided doses for 3 months (ACG [Lichtenstein 2018]); begin as soon as oral intake is resumed after surgery and administer in combination with a thiopurine (azathioprine or mercaptopurine) or a TNF-alpha inhibitor (eg, adalimumab) (De Cruz 2015; D’Haens 2008).
Treatment of simple perianal fistulas, adjunctive agent: Oral: 500 mg twice daily for 4 weeks initially; if clinical response (ie, cessation of drainage and closure of fistula), continue at 250 mg 3 times daily for an additional 4 weeks (Bitton 2019) or 10 to 20 mg/kg/day in divided doses for 4 to 8 weeks with or without ciprofloxacin (ACG [Lichtenstein 2018]).
Dientamoeba fragilis infection (off-label use): Oral: 500 to 750 mg 3 times daily for 10 days (CDC 2012; Nagata 2012).
Giardiasis (alternative agent) (off-label use): Oral: 250 mg 3 times daily or 500 mg 2 times daily for 5 to 7 days (Bartelt 2020; Drugs for Parasitic Infections 2013; Ordonez-Mena 2017).
Helicobacter pylori eradication (off-label use):
Clarithromycin triple regimen: Oral: Metronidazole 500 mg 3 times daily in combination with clarithromycin 500 mg twice daily and a standard-dose or double-dose proton pump inhibitor (PPI) twice daily; continue regimen for 14 days. Note: Avoid use of clarithromycin triple therapy in patients with risk factors for macrolide resistance (eg, prior macrolide exposure, local clarithromycin resistance rates ≥15%) (ACG [Chey 2017]; Fallone 2016).
Bismuth quadruple regimen: Oral: Metronidazole 250 mg 4 times daily or 500 mg 3 or 4 times daily in combination with either bismuth subsalicylate 300 to 524 mg or bismuth subcitrate 120 to 300 mg 4 times daily, tetracycline 500 mg 4 times daily, and a standard-dose PPI twice daily; continue regimen for 10 to 14 days (ACG [Chey 2017]; Fallone 2016). Note: When used for salvage therapy, high-dose metronidazole (500 mg 3 or 4 times daily) is recommended with a total regimen duration of 14 days (Shah 2021).
Concomitant regimen: Oral: Metronidazole 500 mg twice daily in combination with clarithromycin 500 mg twice daily, amoxicillin 1 g twice daily, and a standard-dose PPI twice daily; continue regimen for 10 to 14 days (ACG [Chey 2017]; Fallone 2016).
Sequential regimen (alternative regimen): Oral: Amoxicillin 1 g twice daily plus a standard-dose PPI twice daily for 5 to 7 days; then follow with clarithromycin 500 mg twice daily, metronidazole 500 mg twice daily, and a standard-dose PPI twice daily for 5 to 7 days (ACG [Chey 2017]); some experts prefer the 10-day sequential regimen (amoxicillin for 5 days, followed by metronidazole and clarithromycin for 5 days) over the 14-day sequential regimen (amoxicillin for 7 days, followed by metronidazole and clarithromycin for 7 days) due to the lack of data showing superiority of the 14-day regimen over the 10-day regimen in North America (ACG [Chey 2017]; Crowe 2020).
Hybrid regimen (alternative regimen): Oral: Amoxicillin 1 g twice daily plus a standard-dose PPI twice daily for 7 days; then follow with amoxicillin 1 g twice daily, clarithromycin 500 mg twice daily, metronidazole 500 mg twice daily, and a standard-dose PPI twice daily for 7 days (ACG [Chey 2017]; Wang 2015).
Intra-abdominal infection:
Note: Empiric oral regimens may be appropriate for patients with mild to moderate infection. Other patients may be switched from IV to oral therapy at the same dose when clinically improved and able to tolerate an oral diet (SIS [Mazuski 2017]; SIS/IDSA [Solomkin 2010]). The addition of metronidazole may not be necessary for uncomplicated biliary infection of mild to moderate severity (SIS/IDSA [Solomkin 2010]; Vollmer 2021).
Oral, IV: 500 mg every 8 hours as part of an appropriate combination regimen. Duration of therapy is 4 to 5 days following adequate source control (Sawyer 2015; SIS [Mazuski 2017]); for diverticulitis or uncomplicated appendicitis managed without intervention, duration is 7 to 10 days (Barshak 2021; Pemberton 2021).
Intracranial abscess (brain abscess, intracranial epidural abscess) : IV: 7.5 mg/kg (usually 500 mg) every 6 to 8 hours (maximum dose: 4 g/day) for 6 to 8 weeks in combination with other appropriate antimicrobial therapy (Bodilsen 2018; Sexton 2021; Southwick 2021; manufacturer's labeling). Note: May switch IV metronidazole to oral metronidazole at the same dose to complete treatment course (Southwick 2021).
Periodontitis, severe (off-label use): Oral: 500 mg every 8 hours in combination with amoxicillin for 7 to 14 days; used in addition to periodontal debridement (Chow 2019; McGowan 2018; Wilder 2020).
Pneumonia, aspiration (alternative agent): Oral, IV: 500 mg 3 times daily in combination with an appropriate beta-lactam (eg, oral amoxicillin, IV penicillin, or an IV third-generation cephalosporin) for 7 days (Bartlett 2018).
Pouchitis (post ileal pouch-anal anastomosis), acute (off-label use):
Initial therapy (alternative agent): Oral: 500 mg every 12 hours for 14 days (Navaneethan 2009; Nguyen 2019; Shen 2020; Wall 2011).
Refractory disease: Oral: 500 mg every 12 hours in combination with ciprofloxacin for 28 days (Benlice 2019; Shen 2020).
Sexually transmitted infections:
Bacterial vaginosis:
Note: Treatment is generally not warranted for asymptomatic patients who are not pregnant (CDC [Workowski 2021]).
Oral: 500 mg twice daily for 7 days (CDC [Workowski 2021]; SOGC [Yudin 2017]). For multiple disease recurrences, 500 mg twice daily for 7 days in combination with or prior to a multi-week course of boric acid, followed by suppressive topical therapy (CDC [Workowski 2021]; Reichman 2009; Sobel 2021a).
Empiric treatment following sexual assault in females (off-label use): Oral: 500 mg twice daily for 7 days, as part of an appropriate combination regimen (CDC [Workowski 2021]).
Pelvic inflammatory disease: Oral, IV: 500 mg every 12 hours for 14 days as part of an appropriate combination regimen (CDC [Workowski 2021]).
Trichomoniasis (index case and sex partner):
Initial treatment:
Females: Oral: 500 mg twice daily for 7 days. Note: Single 2 g dose is no longer preferred due to inferior efficacy (CDC [Workowski 2021]; Howe 2017; Kissinger 2010; Kissinger 2018), but some experts suggest it may be used in patients unable to complete multiple dose treatment course (Sobel 2021b).
Males: Oral: 2 g as a single dose (CDC [Workowski 2021]).
Persistent or recurrent infection (ie, treatment failure of nitroimidazole [eg, metronidazole]):
Females following re-exposure to an untreated partner: Oral: 500 mg twice daily for 7 days (CDC [Workowski 2021]).
Females without re-exposure: Oral: 2 g once daily for 7 days. Note: Clinicians may request a kit from the CDC to perform drug resistance testing (CDC [Workowski 2021]).
Males following re-exposure to an untreated partner: Oral: 2 g as a single dose (CDC [Workowski 2021]).
Males without re-exposure: Oral: 500 mg twice daily for 7 days. Note: Clinicians may request a kit from the CDC to perform drug resistance testing (CDC [Workowski 2021]).
Skin and soft tissue infection:
Necrotizing infection (as a component of an appropriate combination regimen) (alternative agent): IV: 500 mg every 6 hours. Continue until further debridement is not necessary, patient has clinically improved, and patient is afebrile for 48 to 72 hours (IDSA [Stevens 2014]).
Surgical site infection, incisional (eg, intestinal or GU tract; axilla or perineum), warranting anaerobic coverage: IV: 500 mg every 8 hours in combination with other appropriate agents. Duration depends on severity, need for debridement, and clinical response (IDSA [Stevens 2014]).
Surgical prophylaxis:
IV: 500 mg within 60 minutes prior to surgical incision in combination with other antibiotics. Considered a recommended agent for select procedures involving the GI tract, urologic tract, or head and neck (Bratzler 2013).
Oral:
Colorectal surgical prophylaxis (off-label use): 1 g every 3 to 4 hours for 3 doses with additional oral antibiotics, starting after mechanical bowel preparation the evening before a morning surgery and followed by an appropriate IV antibiotic prophylaxis regimen (Bratzler 2013).
Uterine evacuation (induced abortion or pregnancy loss) (alternative agent) (off-label use): 500 mg as a single dose 1 hour prior to uterine aspiration; may be administered up to 12 hours before the procedure (ACOG 2018; Shih 2020). Note: The optimal dosing regimen has not been established; various protocols are in use (Achilles 2011).
Tetanus ( Clostridium tetani infection) (off-label use): Oral, IV: 500 mg every 6 to 8 hours for 7 to 10 days in combination with supportive therapy (Ahmadsyah 1985; Sexton 2020a).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
The renal dosing recommendations are based upon the best available evidence and clinical expertise. Senior Editorial Team: Bruce Mueller, PharmD, FCCP, FASN, FNKF; Jason Roberts, PhD, BPharm (Hons), B App Sc, FSHP, FISAC; Michael Heung, MD, MS.
Decreased kidney function does not impact serum half-life of metronidazole but is associated with accumulation of the active hydroxyl and almost inactive acetic acid metabolites (Bergan 1986; Houghton 1985; Lamp 1999). Kidney dysfunction may confer a higher risk of CNS side effects, such as neuropathy, encephalopathy, and seizures (Sarna 2013).
Note: Single-dose regimens (eg, 2 g once) do not require dose adjustment (expert opinion).
Altered kidney function:
IV, Oral:
CrCl ≥10 mL/minute: No dosage adjustment necessary (expert opinion; manufacturer's labeling); however, monitor closely for adverse effects due to accumulation of metabolites in patients with more severe impairment (CrCl <30 mL/minute), particularly with prolonged courses of therapy (Bergan 1986).
CrCl <10 mL/minute: No dosage adjustment necessary (expert opinion; manufacturer's labeling); however, monitor closely for adverse effects due to accumulation of metabolites, particularly with prolonged courses of therapy. A dose of 500 mg every 12 hours may be adequate to achieve therapeutic plasma levels for nonsevere non-Clostridioides difficile infections (Somogyi 1984).
Hemodialysis, intermittent (thrice weekly): Dialyzable (42% to 65% metronidazole and hydroxyl and acetic acid metabolites [Lau 1986]):
IV, Oral: Usual dose: 500 mg every 8 to 12 hours (Heintz 2009). Note: Larger doses may be utilized depending on clinical indication, but with close monitoring for adverse effects, particularly if the treatment course is >1 to 2 weeks in duration (expert opinion). On dialysis days, administer after dialysis. If administration cannot be separated from hemodialysis, consider supplemental dose following hemodialysis.
Peritoneal dialysis: Minimally dialyzed (10% removal with single long dwell; manufacturer's labeling):
IV, Oral: No dosage adjustment necessary (Cassey 1983; Guay 1984). Monitor for adverse effects due to metabolite accumulation, particularly if the treatment course is >1 to 2 weeks in duration (expert opinion).
CRRT:
Note: Drug clearance is dependent on the effluent flow rate, filter type, and method of renal replacement. Recommendations are based on high-flux dialyzers and effluent flow rates of 20 to 25 mL/kg/hour (or ~1,500 to 3,000 mL/hour) unless otherwise noted. Appropriate dosing requires consideration of adequate drug concentrations (eg, site of infection). Close monitoring of response and adverse reactions (eg, neurotoxicity) due to metabolite accumulation is important:
IV, Oral: No dosage adjustment necessary (Heintz 2009; expert opinion).
PIRRT (eg, sustained, low-efficiency diafiltration):
Note: Drug clearance is dependent on the effluent flow rate, filter type, and method of renal replacement. Appropriate dosing requires consideration of adequate drug concentrations (eg, site of infection). Close monitoring of response and adverse reactions (eg, neurotoxicity) due to drug accumulation is important:
IV, Oral: No dosage adjustment necessary (expert opinion). On PIRRT days, administer after PIRRT session. If administration cannot be separated from PIRRT, consider supplemental dose following completion of PIRRT session.
Manufacturer’s labeling:
Mild or moderate impairment (Child-Pugh class A or B): No dosage adjustment necessary; use with caution and monitor for adverse events.
Severe impairment (Child-Pugh class C):
Capsules:
Amebiasis: 375 mg 3 times daily
Trichomoniasis: 375 mg once daily
Tablets, injection: Reduce dose by 50%
Alternative dosing: The pharmacokinetics of a single oral 500 mg dose were not altered in patients with cirrhosis; initial dose reduction is therefore not necessary (Daneshmend 1982). In one study of IV metronidazole, patients with alcoholic liver disease (with or without cirrhosis) demonstrated a prolonged elimination half-life (eg, ~18 hours). The authors recommended the dose be reduced accordingly (clearance was reduced by ~62%) and the frequency may be prolonged (eg, every 12 hours instead of every 6 hours) (Lau 1987). In another single IV dose study using metronidazole metabolism to predict hepatic function, patients classified as Child-Pugh class C demonstrated a half-life of ~21.5 hours (Muscara 1995).
(For additional information see "Metronidazole (systemic): Pediatric drug information")
Note: Some clinicians recommend using adjusted body weight in obese children. Dosing weight = IBW + 0.45 (TBW-IBW)
General dosing, susceptible infection (Red Book [AAP 2018]): Infants, Children, and Adolescents:
Oral: 15 to 50 mg/kg/day in divided doses 3 times daily; maximum daily dose: 2,250 mg/day.
IV: 22.5 to 40 mg/kg/day in divided doses 3 or 4 times daily; maximum daily dose: 4,000 mg/day.
Amebiasis: Infants, Children, and Adolescents: Oral: 35 to 50 mg/kg/day in divided doses every 8 hours for 7 to 10 days; maximum dose: 750 mg/dose; for severe infection or extraintestinal disease, IV may be necessary (Bradley 2018; Red Book [AAP 2018]).
Appendicitis, perforated (divided dosing): Children and Adolescents: IV: 10 mg/kg/dose every 8 hours (Emil 2003).
Appendicitis, perforated (once-daily dosing): Limited data available: Children and Adolescents: IV: 30 mg/kg/dose once daily in combination with ceftriaxone; maximum reported daily dose: 1,500 mg/day (Yardeni 2013); however, other pediatric trials did not report a maximum; in adult patients, a maximum daily dose of 1,500 mg/day for once-daily dosing is suggested (IDSA [Solomkin 2010]); in pediatric patients, once-daily metronidazole in combination with ceftriaxone has been shown to have similar efficacy as triple-combination therapy with ampicillin, clindamycin, and gentamicin (Fraser 2010; St Peter 2006; St Peter 2008).
Balantidiasis: Infants, Children, and Adolescents: Oral: 35 to 50 mg/kg/day in divided doses every 8 hours for 5 days; maximum dose: 750 mg/dose (Red Book [AAP 2018]).
Catheter (peritoneal dialysis); exit-site or tunnel infection: Infants, Children, and Adolescents: Oral: 10 mg/kg/dose 3 times daily. Maximum dose: 500 mg/dose (ISPD [Warady 2012]).
Clostridioides difficile infection:
Infants: Mild to moderate infection: Oral, IV: 7.5 mg/kg/dose every 6 hours for 10 days (Red Book [AAP 2018]).
Children and Adolescents:
Non-severe infection, initial or first recurrence: Oral: 7.5 mg/kg/dose 3 to 4 times daily for 10 days; maximum dose: 500 mg/dose (IDSA/SHEA [McDonald 2018]).
Severe/fulminant infection, initial: IV: 10 mg/kg/dose every 8 hours for 10 days; maximum dose: 500 mg/dose; use concomitantly with oral or rectal vancomycin (IDSA/SHEA [McDonald 2018]).
Dientamoeba fragilis: Infants, Children, and Adolescents: Oral: 35 to 50 mg/kg/day in divided doses every 8 hours for 10 days; maximum dose: 750 mg/dose (Red Book [AAP 2018]).
Giardiasis: Infants, Children, and Adolescents: Oral: 5 to 10 mg/kg/dose every 8 hours for 5 to 7 days; maximum dose: 250 mg/dose (Bradley 2018; Gardner 2001; Granados 2012; Ross 2013; Red Book [AAP 2018]).
Helicobacter pylori eradication: Limited data available: Note: Use as part of an appropriate combination regimen; usual duration of therapy is 14 days (NASPGHAN/ESPGHAN [Jones 2017]).
Weight-directed dosing: Children and Adolescents: Oral: 10 to 15 mg/kg/dose twice daily; maximum dose: 500 mg/dose (Bontems 2011; Butenko 2017; Huang 2013; Iwańczak 2016; Koletzko 2011; Kutluk 2016; Schwarzer 2011).
Fixed dosing (NASPGHAN/ESPGHAN [Jones 2017]): Children and Adolescents:
15 to <25 kg: Oral: 250 mg twice daily.
25 to <35 kg: Oral: 500 mg in the morning and 250 mg in the evening or 375 mg twice daily (if using liquid preparation).
≥35 kg: Oral: 500 mg twice daily.
Inflammatory bowel disease:
Crohn disease, perianal disease; induction: Children and Adolescents: Oral: 7.5 mg/kg/dose 3 times daily for 6 weeks with or without ciprofloxacin; maximum dose: 500 mg/dose (Sandhu 2010).
Ulcerative colitis, pouchitis, persistent: Children and Adolescents: Oral: 20 to 30 mg/kg/day in divided doses 3 times daily for 14 days with or without ciprofloxacin or oral budesonide; maximum dose: 500 mg/dose (Turner 2012).
Intra-abdominal infection: Infants, Children, and Adolescents: IV: 30 to 40 mg/kg/day in divided doses 3 times daily as part of combination therapy; maximum dose: 500 mg/dose (IDSA [Solomkin 2010]).
Pelvic inflammatory disease: Adolescents: Oral: 500 mg twice daily for 14 days; give with doxycycline plus a cephalosporin (CDC [Workowski 2015]).
Peritonitis (peritoneal dialysis) (ISPD [Warady 2012]):
Prophylaxis: Gastrointestinal or genitourinary procedures: Infants, Children, and Adolescents: IV: 10 mg/kg once prior to procedure in combination with cefazolin; Maximum dose: 1,000 mg/dose.
Treatment: Infants, Children, and Adolescents: Oral: 10 mg/kg/dose 3 times daily. Maximum daily dose: 1,200 mg/day.
Prophylaxis against sexually transmitted diseases following sexual assault (CDC [Workowski 2015]): Adolescents: Oral: 2,000 mg as a single dose in combination with azithromycin and ceftriaxone.
Surgical prophylaxis: Children and Adolescents: IV: 15 mg/kg as a single dose 30 to 60 minutes prior to procedure; maximum single dose: 500 mg (IDSA/ASHP [Bratzler 2013]).
Surgical prophylaxis, colorectal: Children and Adolescents: Oral: 15 mg/kg/dose 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; maximum dose: 1,000 mg/dose (IDSA/ASHP [Bratzler 2013]).
Tetanus (Clostridium tetani infection): Infants, Children, and Adolescents: IV, Oral: 30 mg/kg/day in divided doses 4 times daily for 7 to 10 days; maximum daily dose: 4,000 mg/day (Red Book [AAP 2018]).
Trichomoniasis; treatment: Oral:
Children <45 kg: 45 mg/kg/day in divided doses 3 times daily for 7 days; maximum daily dose: 2,000 mg/day (Red Book [AAP 2018]).
Children ≥45 kg and Adolescents: 500 mg twice daily for 7 days or 2,000 mg as a single dose once (CDC [Workowski 2015]; Red Book [AAP 2018]). Note: 7-day-course has been shown to be more effective in adult women (Howe 2017; Kissinger 2010; Kissinger 2018).
Vaginosis, bacterial: Oral: Children >45 kg and Adolescents: 500 mg twice daily for 7 days (CDC [Workowski 2015]; Red Book [AAP 2018]).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Infants, Children, and Adolescents:
Manufacturer's labeling:
Mild, moderate, or severe impairment: There are no dosage adjustments provided in the manufacturer's labeling; however, decreased renal function does not alter the single-dose pharmacokinetics.
ESRD requiring dialysis: Metronidazole metabolites may accumulate; monitor for adverse events; accumulated metabolites may be rapidly removed by dialysis.
Intermittent hemodialysis (IHD): If administration cannot be separated from hemodialysis, consider supplemental dose following hemodialysis.
Peritoneal dialysis (PD): No dosage adjustment necessary
Alternate dosing: Others have used the following adjustments (Aronoff 2007). Note: Renally adjusted dose recommendations are based on doses of 15 to 30 mg/kg/day divided every 6 to 8 hours.
GFR ≥10 mL/minute/1.73 m2: No adjustment required
GFR <10 mL/minute/1.73 m2: 4 mg/kg/dose every 6 hours
Intermittent hemodialysis (IHD): Extensively removed by hemodialysis: 4 mg/kg/dose every 6 hours
Peritoneal dialysis (PD): Extensively removed by peritoneal dialysis: 4 mg/kg/dose every 6 hours
Continuous renal replacement therapy (CRRT): No adjustment required
Infants, Children, and Adolescents:
Manufacturer labeling:
Mild or moderate impairment (Child-Pugh class A or B): No dosage adjustment necessary; use with caution and monitor for adverse events.
Severe impairment (Child-Pugh class C): Immediate-release tablets, injection: Reduce dose by 50%.
Alternate dosing: The pharmacokinetics of a single oral 500 mg dose were not altered in patients with cirrhosis; initial dose reduction is therefore not necessary (Daneshmend 1982). In one study of IV metronidazole, adult patients with alcoholic liver disease (with or without cirrhosis) demonstrated a prolonged elimination half-life (eg, ~18 hours). The authors recommended the dose be reduced accordingly (clearance was reduced by ~62%) and the frequency may be prolonged (eg, every 12 hours instead of every 6 hours) (Lau 1987). In another single IV dose study using metronidazole metabolism to predict hepatic function, patients classified as Child-Pugh class C demonstrated a half-life of ~21.5 hours (Muscara 1995).
Refer to adult dosing.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Capsule, Oral:
Flagyl: 375 mg
Generic: 375 mg
Solution, Intravenous:
Generic: 500 mg (100 mL)
Solution, Intravenous [preservative free]:
Generic: 500 mg (100 mL); 5 mg/mL (100 mL [DSC])
Tablet, Oral:
Flagyl: 250 mg [DSC], 500 mg
Generic: 250 mg, 500 mg
Yes
Parenteral solution contains 28 mEq of sodium/gram of metronidazole.
First-Metronidazole oral suspension is a compounding kit. Refer to manufacturer's labeling for compounding instructions.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule, Oral:
Flagyl: 500 mg [contains brilliant blue fcf (fd&c blue #1), fd&c yellow #10 (quinoline yellow)]
Generic: 500 mg
Solution, Intravenous:
Generic: 5 mg/mL (100 mL)
Tablet, Oral:
Generic: 250 mg
IV: Infuse intravenously over 30 to 60 minutes. Avoid contact of drug solution with equipment containing aluminum.
Oral: Administer with food to minimize stomach upset.
Oral: May administer with food to minimize GI upset.
Parenteral: IV: Administer undiluted (5 mg/mL) by slow intermittent infusion over 30 to 60 minutes. Avoid contact of drug solution with equipment containing aluminum.
Amebiasis: Treatment of acute intestinal amebiasis (amebic dysentery) and extraintestinal amebiasis (liver abscess)
Limitations of use: When used for amebic liver abscess, may be used concurrently with percutaneous needle aspiration when clinically indicated.
Anaerobic bacterial infections (caused by Bacteroides spp. , including the B. fragilis group):
Bacterial septicemia: Treatment of bacterial septicemia (also caused by Clostridium spp.)
Bone and joint infections: Treatment (adjunctive therapy) of bone and joint infections
CNS Infections: Treatment of CNS infections, including meningitis and brain abscess
Endocarditis: Treatment of endocarditis
Gynecologic infections: Treatment of gynecologic infections including endometritis, endomyometritis, tubo-ovarian abscess, and postsurgical vaginal cuff infection (also caused by Clostridium spp., Peptococcus spp., Peptostreptococcus spp., and Fusobacterium spp.)
Intra-abdominal infections: Treatment of intra-abdominal infections, including peritonitis, intra-abdominal abscess, and liver abscess (also caused by Clostridium spp., Eubacterium spp., Peptococcus spp., and Peptostreptococcus spp.)
Lower respiratory tract infections: Treatment of lower respiratory tract infections, including pneumonia, empyema, and lung abscess
Skin and skin structure infections: Treatment of skin and skin structure infections (also caused by Clostridium spp., Peptococcus spp., Peptostreptococcus spp., and Fusobacterium spp.)
Surgical prophylaxis (colorectal surgery): Injection: Preoperative, intraoperative, and postoperative prophylaxis to reduce the incidence of postoperative infection in patients undergoing elective colorectal surgery classified as contaminated or potentially contaminated
Trichomoniasis: Treatment of infections caused by Trichomonas vaginalis, including treatment of asymptomatic sexual partners
Balantidiasis; Bite wound infection, prophylaxis or treatment (animal or human bite); Clostridioides difficile infection, treatment; Crohn disease; Dientamoeba fragilis infection; Empiric treatment (of sexually transmitted infections) in females following sexual assault; Giardiasis; Helicobacter pylori eradication; Periodontitis, severe; Pouchitis (post ileal pouch-anal anastomosis), acute; Surgical prophylaxis, colorectal surgery (oral metronidazole); Surgical prophylaxis, uterine evacuation (induced abortion or pregnancy loss); Tetanus
MetroNIDAZOLE may be confused with mebendazole, meropenem, metFORMIN, methotrexate, metoclopramide, miconazole
Metronidazole has been associated with a range of CNS effects, which include peripheral neuropathy (Ref), aseptic meningitis (Ref), ataxia (Ref), neurocerebellar toxicity (Ref), confusion or disorientation (Ref), dysarthria (Ref), encephalopathy (Ref), seizures (Ref), optic neuropathy (Ref), and vertigo (Ref). Most reports have occurred in adults; however, there are reports in pediatric patients (Ref). CNS effects are generally reversible within days to weeks of discontinuation of therapy (Ref); however, some cases may not be reversible (Ref). Peripheral neuropathy symptoms may be prolonged after discontinuation.
Mechanism: Unclear; proposed mechanisms include binding to neural RNA inhibiting protein synthesis, modulation of inhibitory neurotransmitters gamma-aminobutyric acid receptors within the cerebellar and vestibular systems, reversible mitochondrial dysfunction, and vasogenic and cytotoxic edema (Ref).
Onset: Varied; median of 28 days was reported in a systematic review of metronidazole-induced encephalopathy (Ref) and a median of 54 days was reported in another systematic review (Ref); however, both reviews reported that some cases took less than a week.
Risk factors:
May include:
• High doses, high cumulative doses, or prolonged or repeated courses (Ref)
Limited cases of disulfiram-like reactions with metronidazole have been reported in the literature in both adults and pediatric patients when used with alcohol (Ref). Of note, literature reviews have noted limited clinical data supporting this reaction and suggest that the risk of such a reaction is unclear (Ref). The proposed mechanism is inhibition of aldehyde dehydrogenase), which results in the accumulation of aldehydes (Ref). In one case report, onset was rapid, occurring after 2 days (Ref). No risk factors have been identified.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.
>10%:
Gastrointestinal: Nausea (10% to 12%)
Genitourinary: Vaginitis (15%)
Nervous system: Headache (18%)
1% to 10%:
Dermatologic: Genital pruritus (5%)
Gastrointestinal: Abdominal pain (4%), diarrhea (4%), xerostomia (2%)
Genitourinary: Dysmenorrhea (3%), urinary tract infection (2%), urine abnormality (3%)
Infection: Bacterial infection (7%), candidiasis (3%)
Nervous system: Dizziness (4%), metallic taste (9%)
Respiratory: Flu-like symptoms (6%), pharyngitis (3%), rhinitis (4%), sinusitis (3%), upper respiratory tract infection (4%)
Frequency not defined:
Cardiovascular: Chest pain, facial edema, flattened T-wave on ECG, flushing, palpitations, peripheral edema, syncope, tachycardia
Dermatologic: Erythematous rash, hyperhidrosis, pruritus, urticaria
Endocrine & metabolic: Decreased libido
Gastrointestinal: Abdominal cramps, anorexia, constipation, decreased appetite, dysgeusia, epigastric discomfort, glossitis, hairy tongue, proctitis, stomatitis, vomiting
Genitourinary: Cystitis, dark urine (rare), dyspareunia, dysuria, urinary incontinence, urine discoloration, vaginal dryness, vulvovaginal candidiasis
Hematologic & oncologic: Agranulocytosis, eosinophilia
Immunologic: Drug reaction with eosinophilia and systemic symptoms
Local: Inflammation at injection site, injection site reaction
Nervous system: Chills, depression, drowsiness, epilepsy, hypoesthesia, insomnia, irritability, malaise, numbness, psychosis
Neuromuscular & skeletal: Arthralgia, asthenia, muscle spasm, myalgia
Ophthalmic: Abnormal eye movements (saccadic), nystagmus disorder
Renal: Polyuria
Respiratory: Dyspnea, nasal congestion
Miscellaneous: Fever
Postmarketing:
Cardiovascular: Prolonged QT interval on ECG (Gnanapandithan 2021; Mojadidi 2016)
Dermatologic: Stevens-Johnson syndrome (Mazumdar 2014), toxic epidermal necrolysis (Ali 2021)
Gastrointestinal: Pancreatitis (rare) (O’Halloran 2010; Yilmaz 2016; Youssef 2019)
Hematologic & oncologic: Leukopenia (Taylor 1965), neutropenia (reversible) (Khan 2008), thrombocytopenia (reversible, rare) (Lew 2017)
Hepatic: Acute hepatic failure (especially in Cockayne syndrome) (Ataee 2020), hepatotoxicity (including severe hepatotoxicity, especially in Cockayne syndrome) (Hestin 1994)
Hypersensitivity: Anaphylaxis (Asensio Sánchez 2008)
Immunologic: Serum sickness-like reaction (joint pains) (VanCleave 2016)
Nervous system: Aseptic meningitis (Khan 2007), ataxia (Sagvekar 2019), confusion (Kuriyama 2011), disulfiram-like reaction (with alcohol) (Alonzo 2019), dysarthria (Boot 2017), encephalopathy (Roy 2016), mania (Puri 2021), neurocerebellar toxicity (Patel 2008), paresthesia (Soh 2021), peripheral neuropathy (Goolsby 2018), seizure (Huang 2012), vertigo (Chen 2013)
Ophthalmic: Optic neuropathy (Chen 2013)
Hypersensitivity to metronidazole, nitroimidazole derivatives, or any component of the formulation; pregnant patients (first trimester) with trichomoniasis; use of disulfiram within the past 2 weeks; use of alcohol or propylene glycol-containing products during therapy or within 3 days of therapy discontinuation; Cockayne syndrome.
Canadian labeling: Additional contraindications (not in the US labeling): Active neurological disorders; history of blood dyscrasia; hypothyroidism; hypoadrenalism.
Concerns related to adverse effects:
• Superinfection: Prolonged use may result in fungal or bacterial superinfection, including C. difficile-associated diarrhea (CDAD) and pseudomembranous colitis; CDAD has been observed >2 months postantibiotic treatment.
Disease-related concerns:
• Hepatic impairment: Use with caution in patients with hepatic impairment due to potential accumulation; dosage adjustment recommended in patients with severe hepatic impairment.
• Renal impairment: Use with caution in patients with renal impairment due to potential accumulation; dosage adjustments may be required.
• Seizure disorder: Use with caution in patients with a history of seizure disorder.
Dosage-form specific issues:
• Injection: Use injection with caution in patients with heart failure, edema, or other sodium-retaining states, including corticosteroid treatment due to high sodium content. In patients receiving continuous nasogastric secretion aspiration, sufficient metronidazole may be removed in the aspirate to cause a reduction in serum levels.
Substrate of CYP2A6 (major); Note: Assignment of Major/Minor substrate status based on clinically relevant drug interaction potential; Inhibits CYP2C9 (weak)
Alcohol (Ethyl): MetroNIDAZOLE (Systemic) may enhance the adverse/toxic effect of Alcohol (Ethyl). A disulfiram-like reaction may occur. Risk X: Avoid combination
BCG (Intravesical): Antibiotics may diminish the therapeutic effect of BCG (Intravesical). Risk X: Avoid combination
BCG Vaccine (Immunization): Antibiotics may diminish the therapeutic effect of BCG Vaccine (Immunization). Risk C: Monitor therapy
Busulfan: MetroNIDAZOLE (Systemic) may increase the serum concentration of Busulfan. Management: The toxic effects of busulfan may be greatly increased with concomitant use of metronidazole. This combination should probably be avoided when possible. If these agents must be used together, increased monitoring for busulfan toxicity is recommended. Risk D: Consider therapy modification
Carbocisteine: MetroNIDAZOLE (Systemic) may enhance the adverse/toxic effect of Carbocisteine. Specifically, metronidazole may enhance adverse effects of alcohol that is present in liquid formulations of carbocisteine-containing products. Risk X: Avoid combination
Cholera Vaccine: Antibiotics may diminish the therapeutic effect of Cholera Vaccine. Management: Avoid cholera vaccine in patients receiving systemic antibiotics, and within 14 days following the use of oral or parenteral antibiotics. Risk X: Avoid combination
Disulfiram: May enhance the adverse/toxic effect of MetroNIDAZOLE (Systemic). In particular, the risk for CNS toxicities such as psychosis may be increased. Risk X: Avoid combination
Dronabinol: MetroNIDAZOLE (Systemic) may enhance the adverse/toxic effect of Dronabinol. Specifically, metronidazole may produce severe intolerance to the alcohol contained in the dronabinol oral solution. Risk X: Avoid combination
Fluorouracil Products: MetroNIDAZOLE (Systemic) may increase the serum concentration of Fluorouracil Products. Risk C: Monitor therapy
Fosphenytoin: May decrease the serum concentration of MetroNIDAZOLE (Systemic). MetroNIDAZOLE (Systemic) may increase the serum concentration of Fosphenytoin. Risk C: Monitor therapy
Haloperidol: QT-prolonging Agents (Indeterminate Risk - Caution) may enhance the QTc-prolonging effect of Haloperidol. Risk C: Monitor therapy
Immune Checkpoint Inhibitors: Antibiotics may diminish the therapeutic effect of Immune Checkpoint Inhibitors. Risk C: Monitor therapy
Lactobacillus and Estriol: Antibiotics may diminish the therapeutic effect of Lactobacillus and Estriol. Risk C: Monitor therapy
Lithium: MetroNIDAZOLE (Systemic) may enhance the adverse/toxic effect of Lithium. MetroNIDAZOLE (Systemic) may increase the serum concentration of Lithium. Risk C: Monitor therapy
Lopinavir: MetroNIDAZOLE (Systemic) may enhance the adverse/toxic effect of Lopinavir. Specifically, the combination of metronidazole and lopinavir/ritonavir solution, which contains 42% alcohol, may result in a disulfiram-like reaction. MetroNIDAZOLE (Systemic) may enhance the arrhythmogenic effect of Lopinavir. Management: Avoid the concomitant use of lopinavir/ritonavir and metronidazole if possible. If these agents are used concomitantly, monitor for QTc prolongation/arrhythmia and if the lopinavir/ritonavir solution is used, development of a disulfiram-like reaction. Risk D: Consider therapy modification
Mebendazole: May enhance the adverse/toxic effect of MetroNIDAZOLE (Systemic). Particularly the risk for Stevens-Johnson syndrome or toxic epidermal necrolysis may be increased. Risk X: Avoid combination
Mycophenolate: MetroNIDAZOLE (Systemic) may decrease the serum concentration of Mycophenolate. Specifically, metronidazole may decrease concentrations of the active metabolite of mycophenolate. Risk C: Monitor therapy
PHENobarbital: MetroNIDAZOLE (Systemic) may enhance the adverse/toxic effect of PHENobarbital. A disulfiram-like reaction may occur if combined with phenobarbital dosage forms that contain propylene glycol or alcohol. PHENobarbital may decrease the serum concentration of MetroNIDAZOLE (Systemic). Risk C: Monitor therapy
Phenytoin: MetroNIDAZOLE (Systemic) may enhance the adverse/toxic effect of Phenytoin. A disulfiram-like reaction may occur if combined with phenytoin dosage forms that contain propylene glycol. Phenytoin may decrease the serum concentration of MetroNIDAZOLE (Systemic). MetroNIDAZOLE (Systemic) may increase the serum concentration of Phenytoin. Risk C: Monitor therapy
Primidone: May decrease the serum concentration of MetroNIDAZOLE (Systemic). Risk C: Monitor therapy
Products Containing Propylene Glycol: MetroNIDAZOLE (Systemic) may enhance the adverse/toxic effect of Products Containing Propylene Glycol. A disulfiram-like reaction may occur. Risk X: Avoid combination
QT-prolonging Agents (Highest Risk): QT-prolonging Agents (Indeterminate Risk - Caution) may enhance the QTc-prolonging effect of QT-prolonging Agents (Highest Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Ritonavir: May enhance the adverse/toxic effect of MetroNIDAZOLE (Systemic). Specifically, the combination of ritonavir oral solution or ritonavir soft gelatin capsule, both of which contain alcohol, and metronidazole may result in a disulfiram-like reaction. Risk X: Avoid combination
Sodium Picosulfate: Antibiotics may diminish the therapeutic effect of Sodium Picosulfate. Management: Consider using an alternative product for bowel cleansing prior to a colonoscopy in patients who have recently used or are concurrently using an antibiotic. Risk D: Consider therapy modification
Tipranavir: MetroNIDAZOLE (Systemic) may enhance the adverse/toxic effect of Tipranavir. A disulfiram-like reaction may occur due to the alcohol contained in tipranavir capsules. Risk C: Monitor therapy
TOLBUTamide: CYP2C9 Inhibitors (Weak) may increase the serum concentration of TOLBUTamide. Risk C: Monitor therapy
Typhoid Vaccine: Antibiotics may diminish the therapeutic effect of Typhoid Vaccine. Only the live attenuated Ty21a strain is affected. Management: Avoid use of live attenuated typhoid vaccine (Ty21a) in patients being treated with systemic antibacterial agents. Postpone vaccination until 3 days after cessation of antibiotics and avoid starting antibiotics within 3 days of last vaccine dose. Risk D: Consider therapy modification
Vecuronium: MetroNIDAZOLE (Systemic) may enhance the neuromuscular-blocking effect of Vecuronium. Risk C: Monitor therapy
Vitamin K Antagonists (eg, warfarin): MetroNIDAZOLE (Systemic) may increase the serum concentration of Vitamin K Antagonists. Management: Consider alternatives to concomitant therapy with these agents. If concomitant therapy cannot be avoided, consider reducing the dose of the vitamin K antagonist and monitor for increased INR/bleeding. Risk D: Consider therapy modification
Peak antibiotic serum concentration lowered and delayed, but total drug absorbed not affected.
Metronidazole crosses the placenta.
Cleft lip with or without cleft palate has been reported following first trimester exposure to metronidazole; however, most studies have not shown an increased risk of congenital anomalies or other adverse events to the fetus following maternal use during pregnancy. Because metronidazole was carcinogenic in some animal species, concern has been raised whether metronidazole should be used during pregnancy. Available studies have not shown an increased risk of infant cancer following metronidazole exposure during pregnancy; however, the ability to detect a signal for this may have been limited.
Metronidazole pharmacokinetics are similar between pregnant and nonpregnant patients (Amon 1981; Visser 1984; Wang 2011).
Bacterial vaginosis and vaginal trichomoniasis are associated with adverse pregnancy outcomes (such as premature rupture of membranes, preterm delivery) and metronidazole is recommended for the treatment of symptomatic pregnant patients. The CDC’s recommended twice daily dose of oral metronidazole for the treatment of bacterial vaginosis is the same for nonpregnant and pregnant patients; a three times daily regimen has also been used. Treatment of pregnant patients with asymptomatic bacterial vaginitis who are at high risk for preterm delivery has had mixed results. The CDC recommends the single oral dose regimen for the treatment of vaginal trichomoniasis for both pregnant and nonpregnant patients. Although use of oral metronidazole for vaginal trichomoniasis during the first trimester is contraindicated by the manufacturer, available guidelines note treatment can be given at any stage of pregnancy (CDC [Workowski 2021]).
Metronidazole may also be used for the treatment of giardiasis in pregnant patients (some sources recommend second and third trimester administration only) (Gardner 2001; HHS [OI adult 2020]) and symptomatic amebiasis during pregnancy (HHS [OI adult 2020]; Li 1996). Short courses may be used for the treatment of pouchitis or perianal disease in pregnant patients with inflammatory bowel disease; not recommended for planned maintenance therapy (Mahadevan 2019). The use of other agents is preferred when treatment is needed for Clostridioides difficile during pregnancy (ACG [Kelly 2021]). Consult current recommendations for appropriate use in pregnant patients.
Metronidazole and its active hydroxyl metabolite are present in breast milk at concentrations similar to maternal plasma concentrations. Metronidazole and its active metabolite can be detected in the serum of breastfeeding infants (Gray 1961; Heisterberg 1983; Passmore 1988).
Information related to the presence of metronidazole in breast milk is available from multiple studies:
• Metronidazole transfer to breast milk was assessed in 3 women 6, 13, and 14 weeks' postpartum. Metronidazole 2 g was given orally as a single dose. Breastfeeding was withheld for 24 hours after the dose and several milk samples were collected during these 24 hours. The highest average milk concentrations occurred 2 to 4 hours after the dose; the highest reported average milk concentration was 45.8 mcg/mL. Average milk concentrations were ~12.6 mcg/mL 12 to 24 hours after the dose. The half-life of metronidazole in breast milk was ~9 to 10 hours (2 patients). The authors estimated the infant dose received via breast milk to be 21.8 mg in the first 24 hours and an additional 3.5 mg in the second day after the dose. They noted that withholding breastfeeding for 12 to 24 hours would significantly decrease metronidazole exposure to the breastfeeding infant (Erickson 1981). Metabolite concentrations were not measured in this study. The relative infant dose (RID) of metronidazole is 13.7% to 22.9% when calculated using the highest average breast milk concentration reported in the study (45.8 mcg/mL), compared to an oral infant therapeutic dose of 30 to 50 mg/kg/day, providing an estimated daily infant dose via breast milk of 6.87 mg/kg/day.
• A review article used information from 4 published studies to calculate an RID for metronidazole and compare it to other antibiotics. Maternal doses of oral metronidazole used in these studies ranged from 200 to 400 mg 3 times daily (Heisterberg 1983; Passmore 1988; Willis 1978) or a 2 g single oral dose (Erickson 1981). Authors of the review calculated the RID of metronidazole to be 11%, providing a median estimated daily infant dose via breast milk of 1.59 mg/kg/day (van Wattum 2019).
• In general, breastfeeding is considered acceptable when the RID is <10%; when an RID is >25%, breastfeeding should generally be avoided (Anderson 2016; Ito 2000).
• Breast milk was also evaluated following administration of metronidazole 500 mg IV 3 times a day for 2 days to patients following cesarean delivery. Sampling occurred 1 to 2 hours after the dose on the second day of therapy. Metronidazole concentrations were 7.3 to 10.1 mcg/mL (breast milk) and 7.7 to 13.1 mcg/mL (maternal plasma) (Geballa-Koukoula 2018).
Loose stools, oral and perianal Candida growth, and oral thrush have been reported in breastfeeding infants exposed to metronidazole (Passmore 1988).
The manufacturer warns of the risk of carcinogenicity in patients exposed to metronidazole based on animal studies; theoretically, this risk is also present in breastfeeding infants exposed to metronidazole via breast milk. Therefore, the manufacturer recommends a decision be made whether to discontinue breastfeeding or to discontinue the drug, taking into account the importance of treatment to the mother.
Some guidelines note if metronidazole is given, breastfeeding should be withheld for 12 to 24 hours after a single 2 g dose (CDC [Workowski 2021]; WHO 2002); alternatively, the mother may pump and discard breast milk for 24 hours after taking the last metronidazole dose. Use of lower maternal doses may provide lower concentrations of metronidazole in breast milk and use can be considered in patients who are breastfeeding (CDC [Workowski 2021]). Use of other agents is preferred when treating breastfeeding patients for diseases such as Clostridioides difficile infection, or pouchitis or perianal disease in lactating patients with inflammatory bowel disease (ACG [Kelly 2021]).
Take with food to minimize stomach upset.
Sodium: Injectable dosage form may contain sodium.
Ethanol: Use of ethanol is contraindicated during therapy and for 3 days after therapy discontinuation.
Monitor CBC with differential at baseline, during, and after prolonged or repeated courses of therapy. Closely monitor elderly patients and patients with severe hepatic impairment or ESRD for adverse reactions. Neurologic symptoms; observe patients carefully if neurologic symptoms occur and consider discontinuation of therapy.
After diffusing into the organism, interacts with DNA to cause a loss of helical DNA structure and strand breakage resulting in inhibition of protein synthesis and cell death in susceptible organisms
Absorption: Oral: Well absorbed
Distribution: To bile, seminal fluid, bone, liver, and liver abscesses, lung and vaginal secretions; crosses blood-brain barrier; saliva and CSF concentrations similar to those in plasma
Protein binding: <20%
Metabolism: Hepatic (30% to 60%) to several metabolites including an active hydroxyl metabolite which maintains activity ~30% to 65% of the parent compound (Lamp 1999)
Half-life elimination:
Neonates <7 days (Jager-Roman 1982): Within first week of life, more prolonged than with lower GA:
GA 28 to 30 weeks: 75.3 ± 16.9 hours
GA 32 to 35 weeks: 35.4 ± 1.5 hours
GA 36 to 40 weeks: 24.8 ± 1.6 hours
Neonates ≥7 days: ~22.5 hours (Upadhyaya 1988)
Children and Adolescents: 6 to 10 hours (Lamp 1999)
Adults: ~8 hours
Time to peak, serum: Oral: 1 to 2 hours
Excretion: Urine (unchanged drug and metabolites: 60% to 80%; ~20% of total as unchanged drug); feces (6% to 15%)
Renal function impairment: CrCl ≤65 mL/minute: Half-life: 18 to 32 hours (hydroxy metabolite [active]) (Lamp 1999)
Hepatic function impairment: Half-life: 18.31 hours (mean) in one study (Lau 1987)
According to Child-Pugh classification (Muscara 1995):
Child-Pugh class A: ~10.7 hours
Child-Pugh class B: ~13.5 hours
Child-Pugh class C: ~21.5 hours
Capsules (Flagyl Oral)
375 mg (per each): $7.38
Capsules (metroNIDAZOLE Oral)
375 mg (per each): $12.29
Solution (metroNIDAZOLE in NaCl Intravenous)
500 mg/100 mL 0.74% (per mL): $0.02 - $0.04
500 mg/100 mL 0.79 (per mL): $0.01
Tablets (metroNIDAZOLE Oral)
250 mg (per each): $0.43 - $0.58
500 mg (per each): $0.73 - $0.84
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