Metronidazole

💊 What is Metronidazole used for?

• •Trichomoniasis (T. vaginalis infection) in females and males, when confirmed by lab tests
• •Asymptomatic (no symptoms) trichomoniasis in females when linked to certain cervical conditions named in the label
• •Treatment of sexual partners of people being treated for trichomoniasis, to help prevent reinfection
• •Intestinal amebiasis (amebic dysentery) and amebic liver abscess
• •Serious infections caused by susceptible anaerobic bacteria, including some intra-abdominal infections

How it works

The label describes metronidazole as a synthetic antimicrobial. It is used against parasites and bacteria that the label names. The label does not describe its exact mechanism in the text provided.

How it is usually taken

• •The label says it is taken by mouth as a tablet. Treatment length and schedule differ by infection and may be a single dose or a course of several days or weeks. The label says the dosing should be individualized. Follow the instructions from your prescriber or pharmacist about how and when to take it, and finish the full course if you were prescribed one.

Comes as

• •250 mg tablets
• •500 mg tablets

⚠️ Metronidazole side effects

🛑 Who should not take Metronidazole, and who should be careful

The label says not to take it if

• 🚨You have had an allergic reaction to metronidazole or other nitroimidazole derivatives.
• 🚨You are being treated for trichomoniasis during the first trimester of pregnancy.
• 🚨You have taken disulfiram within the last two weeks. The label says psychotic reactions have been reported in alcoholic patients taking both medicines.
• 🚨You have Cockayne syndrome. The label lists this as a contraindication because of severe liver problems reported after starting the drug.

Tell your doctor before taking it if

• •Tell your prescriber about any past allergic reaction to metronidazole or similar nitroimidazole medicines.
• •Tell your prescriber if you have liver disease, since the label says the drug can build up in people with liver impairment and a reduced dose may be needed in severe cases.
• •Tell your prescriber if you have kidney disease, since the label says the drug and its breakdown products may build up in end-stage kidney disease.
• •Tell your prescriber if you have a history of blood disorders, since the label says caution is needed.
• •Tell your prescriber if you have a yeast infection (candidiasis), since symptoms may be more noticeable during treatment.
• •Tell your prescriber if you are pregnant or may become pregnant, or if you are breastfeeding.
• •Tell your prescriber if you have a history of nervous system problems, since the label describes nerve and brain effects with this drug.

🔀 Metronidazole with other medicines, food and alcohol

The label says to discuss these with your doctor or pharmacist

• •Alcohol and products containing propylene glycol: The label says abdominal cramps, nausea, vomiting, headaches, and flushing may occur. Avoid these during treatment and for at least three days afterward.
• •Disulfiram: Psychotic reactions have been reported. Do not take metronidazole within two weeks of disulfiram.
• •Warfarin and other oral anticoagulants: Metronidazole may increase their effect. The label says prothrombin time and INR should be carefully monitored.
• •Lithium: Short-term use has been linked to higher lithium levels and, in a few cases, lithium toxicity. The label says lithium and creatinine levels should be checked several days after starting.
• •Busulfan: Metronidazole may increase busulfan levels and the risk of serious toxicity. The label says they should not be given together unless the benefit outweighs the risk.
• •Cimetidine: May slow the removal of metronidazole from the body.
• •Phenytoin or phenobarbital: May speed the removal of metronidazole. Impaired clearance of phenytoin has also been reported.
• •Drugs that prolong the QT interval: QT prolongation has been reported when these are used with metronidazole.

Alcohol and food

The label says to stop drinking alcoholic beverages and to avoid products containing propylene glycol while taking metronidazole and for at least three days afterward. It does not give food instructions in the text provided.

🤰 Metronidazole in pregnancy and breastfeeding

Pregnancy

The label says there are no adequate and well-controlled studies in pregnant women. Many studies included first-trimester exposure, and most did not show increased risk of birth defects, but one study showed an increased risk of cleft lip with or without cleft palate that was not confirmed. The label says metronidazole crosses the placenta and its effects on fetal organ development are not known. For trichomoniasis, the label says it should not be used in the first trimester.

Breastfeeding

The label says metronidazole passes into human milk at levels similar to the mother's blood levels. The label notes that the drug is not intended for long-term use. It says the benefits of breastfeeding and the mother's need for the medicine should be weighed together. The label also mentions that a nursing mother may choose to pump and discard milk during treatment.

🗓️ Storage, missed doses and taking too much

Storage

The label text provided does not include storage temperature instructions. It lists bottle packages of 21, 28, or 30 film-coated tablets.

If a dose is missed

The label does not say.

If too much is taken

The label says single oral doses up to 15 g have been reported in suicide attempts and accidental overdoses. Reported symptoms include nausea, vomiting, and ataxia (loss of coordination). Neurotoxic effects, including seizures and peripheral neuropathy, have been reported after repeated high doses. The label says there is no specific antidote, so care is supportive and symptomatic.

🗒️ Questions to ask about Metronidazole

• Which of my symptoms is this medicine meant to treat, and has the infection been confirmed by tests?
• How long will I need to take it, and should I finish the full course?
• Do I need to avoid alcohol, and for how long after my last dose?
• Are any of my other medicines, such as warfarin, lithium, or seizure medicines, affected by metronidazole?
• What signs of a serious skin reaction or nerve problem should I watch for, and who should I call?
• Should my sexual partner also be treated, and how should I protect against reinfection?

❓ Metronidazole: frequently asked questions