Metronidazole — uses, dosing, side effects & the brands that sell it · pharmaranks
Metronidazole: uses, dosing, side effects & brands
Metronidazole is a nitroimidazole antimicrobial sold in the U.S. under 16 brand and generic names, for abscess, amebiasis and bacteroides infections. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
By the pharmaranks editorial team·Reviewed against the FDA (openFDA label, NDC Directory & Enforcement) sources·How we research
From the FDA label for Flagyl (application NDA012623). Other metronidazole products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
Trichomoniasis In the Female: Seven-day course of treatment (375 mg two times daily for seven consecutive days). A seven-day course of treatment may minimize reinfection by protecting the patient long enough for the sexual contacts to obtain treatment. Pregnant patients should not be treated during the first trimester (see CONTRAINDICATIONS and PRECAUTIONS ). When repeat courses of the drug are required, it is recommended that an interval of four to six weeks elapse between courses and that the presence of the trichomonad be reconfirmed by appropriate laboratory measures. Total and differential leukocyte counts should be made before and after re-treatment. In the Male: Treatment should be individualized as it is for the female. Amebiasis: Adults: For acute intestinal amebiasis (acute amebic dysentery): 750 mg orally three times daily for 5 to 10 days. For amebic liver abscess: 750 mg orally three times daily for 5 to 10 days. Pediatric patients: 35 to 50 mg/kg/24 hours, divided into three doses, orally for 10 days. Anaerobic Bacterial Infections In the treatment of most serious anaerobic infections, intravenous metronidazole is usually administered initially. The usual adult oral dosage is 7.5 mg/kg every 6 hours (approximately 500 mg for a 70 kg adult). A maximum of 4 g should not be exceeded during a 24-hour period. The usual duration of therapy is 7 to 10 days; however,…
Metronidazole side effects
The following reactions have been reported during treatment with metronidazole: Central Nervous System: The most serious adverse reactions reported in patients treated with metronidazole have been convulsive seizures, encephalopathy, aseptic meningitis, optic and peripheral neuropathy, the latter characterized mainly by numbness or paresthesia of an extremity. Since persistent peripheral neuropathy has been reported in some patients receiving prolonged administration of metronidazole, patients should be specifically warned about these reactions and should be told to stop the drug and report immediately to their physicians if any neurologic symptoms occur. In addition, patients have reported headache, syncope, dizziness, vertigo, incoordination, ataxia, tinnitus, hearing impairment, hearing loss, confusion, dysarthria, irritability, depression, weakness, and insomnia (see WARNINGS ). Gastrointestinal: The most common adverse reactions reported have been referable to the gastrointestinal tract, particularly nausea, sometimes accompanied by headache, anorexia, and occasionally vomiting; diarrhea; epigastric distress; abdominal cramping; and constipation. Mouth: A sharp, unpleasant metallic taste is not unusual. Furry tongue, glossitis, and stomatitis have occurred; these may be associated with a sudden overgrowth of Candida which may occur during therapy. Dermatologic: Dermatitis…
Metronidazole and food
Alcohol
Avoid alcohol while taking it and for a few days after your last dose, as your prescriber or the label directs. Alcohol can hide in some liquid medicines and mouthwashes.
The elimination half-life of metronidazole is about 8 hours. This is the average for healthy adults with normal kidney and liver function; the half-life is much longer in newborns (roughly 22 to 109 hours, longer the more premature the baby). Metronidazole has an active metabolite (hydroxy-metronidazole) whose levels build up in older adults (40-80% higher) and in severe kidney disease, though the label does not give a separate half-life for it.
Half-life is how long the body takes to clear half a dose. It is not the same as how long a drug test can detect it, and it varies with age, kidney and liver function.
Frequently asked questions
What is metronidazole?
FLAGYL (metronidazole) capsules, 375 mg is an oral formulation of the synthetic nitroimidazole antimicrobial agent, 2-methyl-5-nitro-1 H -imidazole-1-ethanol, which has the following structural formula: FLAGYL (metronidazole) capsules, 375 mg, (indicated below as FLAGYL 375 capsules) contain 375 mg of metronidazole USP. Inactive ingredients include corn starch, magnesium stearate, gelatin, black iron oxide, titanium dioxide, FD&C Green No. 3, and D&C Yellow No. 10. Chemical Structure
What kind of drug is metronidazole?
The FDA classifies metronidazole as a nitroimidazole antimicrobial. Nitroimidazole antibiotics (such as metronidazole) are activated inside oxygen-free bacteria and parasites, where they turn into reactive forms that break and destabilize the microbe's DNA. This kills the germ while largely sparing the body's own cells. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
How long does metronidazole stay in your system?
The elimination half-life of metronidazole is about 8 hours — that is how long the body takes to clear half of a dose. This is the average for healthy adults with normal kidney and liver function; the half-life is much longer in newborns (roughly 22 to 109 hours, longer the more premature the baby). Metronidazole has an active metabolite (hydroxy-metronidazole) whose levels build up in older adults (40-80% higher) and in severe kidney disease, though the label does not give a separate half-life for it. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.
Can you take metronidazole with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run metronidazole against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Who shouldn’t take metronidazole
Hypersensitivity FLAGYL 375 capsules are contraindicated in patients with a prior history of hypersensitivity to metronidazole or other nitroimidazole derivatives. In patients with trichomoniasis, FLAGYL 375 capsules are contraindicated during the first trimester of pregnancy (see PRECAUTIONS ). Psychotic Reaction with Disulfiram Use of oral metronidazole is associated with psychotic reactions in alcoholic patients who were using disulfiram concurrently. Do not administer metronidazole to patients who have taken disulfiram within the last two weeks (see PRECAUTIONS, Drug Interactions ). Interaction with Alcohol Use of oral metronidazole is associated with a disulfiram-like reaction to alcohol, including abdominal cramps, nausea, vomiting, headaches, and flushing. Discontinue consumption of alcohol or products containing propylene glycol during and for at least three days after therapy with metronidazole (see PRECAUTIONS, Drug Interactions ). Cockayne Syndrome FLAGYL 375 capsules are contraindicated in patients with Cockayne syndrome. Severe irreversible hepatotoxicity/acute liver failure with fatal outcomes have been reported after initiation of metronidazole in patients with Cockayne syndrome (see ADVERSE REACTIONS ) .
Metronidazole drug interactions
Disulfiram Psychotic reactions have been reported in alcoholic patients who are using metronidazole and disulfiram concurrently. Metronidazole should not be given to patients who have taken disulfiram within the last 2 weeks (see CONTRAINDICATIONS ). Alcoholic Beverages Abdominal cramps, nausea, vomiting, headaches, and flushing may occur if alcoholic beverages or products containing propylene glycol are consumed during or following metronidazole therapy (see CONTRAINDICATIONS ). Warfarin and other Oral Anticoagulants Metronidazole has been reported to potentiate the anticoagulant effect of warfarin and other oral coumarin anticoagulants, resulting in a prolongation of prothrombin time. When FLAGYL 375 capsules is prescribed for patients on this type of anticoagulant therapy prothrombin time and INR should be carefully monitored. Lithium In patients stabilized on relatively high doses of lithium, short-term metronidazole therapy has been associated with elevation of serum lithium and, in a few cases, signs of lithium toxicity. Serum lithium and serum creatinine levels should be obtained several days after beginning metronidazole to detect any increase that may precede clinical symptoms of lithium intoxication. Busulfan Metronidazole has been reported to increase plasma concentrations of busulfan, which can result in an increased risk for serious busulfan…
We track 16 metronidazole-containing products in the U.S.: Flagyl, Flagyl ER, Vandazole, Flagyl I.V. Rtu in Plastic Container, Likmez, Metro I.V., Metro I.V. in Plastic Container and Metrocream, and 8 more. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does metronidazole come in?
Across the brands we track, metronidazole is currently marketed as capsule, tablet, extended release, topical, injectable, suspension, solution and tablet, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic metronidazole?
Yes. Our catalog lists 2 generic metronidazole products alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.