Metronidazole Dosage

This dosage information may not include all the information needed to use Metronidazole safely and effectively. See additional information for Metronidazole.

The information at Drugs.com is not a substitute for medical advice. ALWAYS consult your doctor or pharmacist.

Usual Adult Dose for Amebiasis

500 to 750 mg orally 3 times a day for 5 to 10 days

Usual Adult Dose for Pseudomembranous Colitis

250 to 500 mg orally 3 to 4 times a day for 10 to 14 days

Usual Adult Dose for Surgical Prophylaxis

Postoperative infection prophylaxis in contaminated or potentially contaminated colorectal surgery:
Preoperative: 15 mg/kg IV infused over 30 to 60 minutes and completed approximately one hour before surgery
Postoperative: 7.5 mg/kg IV infused over 30 to 60 minutes at 6 and 12 hours after the initial dose

Usual Adult Dose for Trichomoniasis

2 g orally one time or 500 mg twice a day for 7 days or 375 mg twice a day for 7 days

The patient's sexual partner(s) should also be evaluated/treated.

Usual Adult Dose for Crohn's Disease - Acute

250 mg orally every 6 hours
Treatment should initially be continued for about four to eight weeks. If no response occurs, the drug should be discontinued. If there is a response, the drug can be continued for about three months, at which time tapering can be attempted. Because of potential dose-related side effects, long-term therapy (greater than 3 to 6 months) is not recommended.

Usual Adult Dose for Crohn's Disease - Maintenance

250 mg orally every 6 hours
Treatment should initially be continued for about four to eight weeks. If no response occurs, the drug should be discontinued. If there is a response, the drug can be continued for about three months, at which time tapering can be attempted. Because of potential dose-related side effects, long-term therapy (greater than 3 to 6 months) is not recommended.

Usual Adult Dose for Dracunculiasis

250 mg orally every 8 hours
Treatment should be continued for about 10 days, depending on the nature and severity of the infection.

Usual Adult Dose for Giardiasis

250 mg orally every 8 hours
Treatment should be continued for about 7 days, depending on the nature and severity of the infection.

Usual Adult Dose for Helicobacter pylori Infection

250 mg orally every 6 hours
Therapy should be continued for approximately 14 days.

Usual Adult Dose for Pelvic Inflammatory Disease

500 mg orally every 12 hours

Oral metronidazole is part of a regimen recommended by the Centers for Disease Control and Prevention (CDC) for the treatment of pelvic inflammatory disease (PID) in the outpatient setting. This outpatient regimen also includes therapy with doxycycline. Both drugs should be given for 14 days. If this patient is acutely ill, parenteral antimicrobial therapy is generally recommended. Many experts recommend that all patients with PID be hospitalized so that supervised treatment with parenteral antimicrobials be initiated. The CDC currently recommend that acutely ill patients with PID be treated with parenteral cefoxitin (or cefotetan) and doxycycline, or parenteral clindamycin and gentamicin. (Metronidazole is not part of the CDC's current recommendations for the treatment of PID in the inpatient setting.)

The patient's sexual partner(s) should also be evaluated/treated.

Usual Adult Dose for Deep Neck Infection

500 mg IV every 6 hours
Therapy should be continued for about 2 to 3 weeks, depending on the nature and severity of the infection.

Usual Adult Dose for Bacterial Vaginosis

500 mg orally every 12 hours for 7 days
Alternatively, 250 mg every 8 hours or extended release tablets 750 mg once daily for 7 days may also be given. Two grams given as a single dose is also effective; however, any treatment failures from this regimen should receive metronidazole for 7 days.

The patient's sexual partner(s) should also be evaluated/treated.

Usual Adult Dose for Aspiration Pneumonia

7.5 mg/kg IV every 6 hours
Intravenous therapy should be continued until the clinical condition stabilizes and fever subsides. Oral therapy may then be substituted. Oral doses are generally equal to intravenous doses. Therapy of documented anaerobic pleuropulmonary infections should be continued until the infiltrate is cleared or a residual scar forms, sometimes for as long as 2 to 4 months.

Usual Adult Dose for Bacteremia

7.5 mg/kg IV every 6 hours
Therapy should be continued for about 14 days, depending on the nature and severity of the infection.

Usual Adult Dose for Meningitis

7.5 mg/kg IV every 6 hours
Therapy should be continued for about 14 days, depending on the nature and severity of the infection.

Usual Adult Dose for Diverticulitis

7.5 mg/kg IV every 6 hours
Therapy should be continued for about 10 to 14 days, depending on the nature and severity of the infection.

Usual Adult Dose for Intraabdominal Infection

7.5 mg/kg IV every 6 hours
Therapy should be continued for about 10 to 14 days, depending on the nature and severity of the infection.

Usual Adult Dose for Peritonitis

7.5 mg/kg IV every 6 hours
Therapy should be continued for about 10 to 14 days, depending on the nature and severity of the infection.

Usual Adult Dose for Endocarditis

7.5 mg/kg IV every 6 hours
Therapy should be continued for about 4 to 6 weeks, depending on the nature and severity of the infection.

Usual Adult Dose for Joint Infection

7.5 mg/kg IV every 6 hours
Therapy should be continued for approximately 3 to 4 weeks, depending on the nature and severity of the infection. Longer therapy, 6 weeks or more, may be required for prosthetic joint infections.

Usual Adult Dose for Osteomyelitis

7.5 mg/kg IV every 6 hours
Therapy should be continued for about 4 to 6 weeks, depending on the nature and severity of the infection. Chronic osteomyelitis may require an additional 1 to 2 months of antibiotic therapy.

Usual Adult Dose for Pneumonia

7.5 mg/kg IV every 6 hours
Therapy should be continued for about 10 to 21 days, depending on the nature and severity of the infection.

Usual Adult Dose for Skin or Soft Tissue Infection

7.5 mg/kg IV every 6 hours
Therapy should be continued for about 7 days or 3 days after resolution of acute inflammation, depending on the nature and severity of the infection. For more severe infections, such as diabetic soft tissue infections, 14 to 21 days of therapy may be required.

Usual Pediatric Dose for Bacterial Infection

Anaerobic infections:
0 to 4 weeks, 1199 g or less: 7.5 mg/kg orally or IV every 24 to 48 hours

7 days or less, 1200 to 2000 g: 7.5 mg/kg orally or IV every 24 hours
7 days or less, 2001 g or more: 7.5 mg/kg orally or IV every 12 hours

8 days to 4 weeks, 1200 to 2000 g: 7.5 mg/kg orally or IV every 12 hours
8 days to 4 weeks, 2001 g or more: 15 mg/kg orally or IV every 12 hours

Infants and children: 7.5 mg/kg orally or IV every 6 hours; maximum dose 4 g/day

Usual Pediatric Dose for Amebiasis

Infants and children: 35 to 50 mg/kg/day orally in 3 divided doses for 10 days

Usual Pediatric Dose for Pseudomembranous Colitis

Infants and children: 20 mg/kg/day orally in 4 divided doses every 6 hours; maximum dose 2 g/day

Usual Pediatric Dose for Trichomoniasis

Infants and children: 15 to 30 mg/kg/day orally in 3 divided doses every 8 hours for 7 days
Adolescents: Adult dosage

The patient's sexual partner(s) should also be evaluated/treated.

Usual Pediatric Dose for Dracunculiasis

Children: 25 mg/kg/day orally in 3 divided doses for 10 days; maximum dose 750 mg/day

Usual Pediatric Dose for Giardiasis

Children: 15 mg/kg/day orally in 3 divided doses
Therapy should be continued for 5 to 10 days, depending on the nature and severity of the infection

Usual Pediatric Dose for Bacterial Vaginosis

Children 44 kg or less: 15 mg/kg/day orally in 2 divided doses for 7 days; maximum dose 1 g/day
Adolescents: Adult dosage

The patient's sexual partner(s) should also be evaluated/treated.

Renal Dose Adjustments

CrCl 9 mL/min or less: The usual dose may be given every 12 hours or half the dose may be given at the usual interval.

Liver Dose Adjustments

Patients with severe hepatic disease metabolize metronidazole slowly, with resultant accumulation of metronidazole and its metabolites in the plasma. Accordingly, for such patients, doses below those usually recommended should be administered cautiously. Close monitoring of plasma metronidazole levels and toxicity is recommended.

Dose Adjustments

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.

Precautions

Metronidazole has been shown to be carcinogenic in mice and rats. Unnecessary use should be avoided and it should be reserved for approved indications.

The use of metronidazole for trichomoniasis is contraindicated during the first trimester of pregnancy.

Encephalopathy, peripheral neuropathy (including optic neuropathy), convulsive seizures, and aseptic meningitis have been reported with metronidazole. Central nervous system (CNS) symptoms associated with encephalopathy (including CNS lesions seen on MRI) are usually reversible within days to weeks following metronidazole discontinuation. Symptoms of aseptic meningitis can occur within hours of administration and typically resolve following metronidazole discontinuation. The prompt evaluation of the benefit/risk ratio of the continuation of IV treatment or the prompt discontinuation of oral therapy is recommended if abnormal neurologic signs and/or symptoms occur. It should be used with caution in patients who have CNS disorders.

Metronidazole should not be administered within 2 weeks of the last dose of disulfiram as psychotic reactions have been reported in alcoholic patients using both agents concurrently.

Metronidazole should be used cautiously in patients with a history of blood dyscrasia. Total and differential leukocyte counts are recommended before and after therapy for trichomoniasis, amebiasis, and anaerobic infections.

To reduce the risk of development of drug-resistant organisms, antibiotics should only be used to treat or prevent proven or suspected infections caused by bacteria. Culture and susceptibility information should be considered when selecting treatment or, if no data are available, local epidemiology and susceptibility patterns may be considered when selecting empiric therapy.

Metronidazole elimination is reduced in neonates. The elimination half-life is prolonged and inversely proportional to the gestational age.

Dialysis

The dose should not be specifically reduced in anuric patients since accumulated metabolites may be rapidly removed by dialysis.

Other Comments

The maximum dose is 4 g/day. Parenteral therapy may be changed to oral metronidazole when conditions warrant, based upon the severity of the disease and the response of the patient. The usual duration of therapy is 7 to 10 days. Infections of the bone and joint, lower respiratory tract, and endocardium may require longer treatment.

Patients should not consume alcohol during treatment and for at least 72 hours after the last dose.

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