• Type of Drug: Amoebicide; antibiotic.
  • Prescribed for: Acute amoebic dysentery; infections of the vagina, bone, brain, nervous system, urinary tract, abdomen, and skin caused by bacteria or other micro-organisms that are sensitive to the drug’s effects. Metronidazole may also be prescribed for pneumonia, inflammatory bowel disease, colitis caused by other antibiotics, periodontal (gum) infections, and some complications of severe liver disease. Metronidazole gel may be applied to the skin to treat acne. It can also be used for severe decubitus (skin) ulcers and inflammation of the skin around the mouth. Metronidazole given by intravenous injection may be used before, during, and after bowel surgery to prevent infectious complications.

General Information

Metronidazole is effective against a variety of fungi and some bacteria. It may be prescribed for symptomless diseases when the doctor feels that an underlying infection may be involved. For example, asymptomatic women may be treated with this drug when vaginal examination shows evidence of Trichomonas. Because vaginal Trichomonas infection is a venereal disease, asymptomatic sexual partners of treated patients should be treated at the same time if the organism has been found in the woman’s genital tract This is needed to prevent reinfection of the partner. The decision to treat an asymptomatic male partner without evidence of infection must be made by the doctor. Metronidazole kills microorganisms by disrupting the DNA of the organism after it enters the cell.

Cautions and Warnings of Generic Flagyl

You should not use this drug if you have a history of blood disease or if you know that you are sensitive or allergic to Metronidazole.

People taking this medication have experienced seizures, numbness, or tingling in the hands or feet. This effect is rare with low doses but may be more common in people taking larger doses for long periods (i.e., in Crohn’s disease).

If this happens to you, stop taking the medicine and call your doctor at once. Metronidazole should be taken with caution if you have active nervous-system disease (including epilepsy) or if you have severe liver problems.

Possible Side Effects

  • Most common: gastrointestinal (GI) tract symptoms, including nausea (sometimes accompanied by headache), dizziness, loss of appetite, occasional vomiting, diarrhea, stomach upset, abdominal cramping, and constipation. A sharp, unpleasant metallic taste is also associated with the use of this drug.
  • Less common: numbness or tingling in the extremities and occasional joint pains, confusion, irritability, depression, difficulty sleeping, and weakness. Itching and a sense of pelvic pressure also have been reported.
  • Rare: clumsiness or poor coordination, fever, increased urination, seizures, incontinence, and reduced sex drive.

Drug Interactions

  • Avoid alcoholic beverages.: Interaction with Metronidazole may cause abdominal cramps, nausea, vomiting, headaches, and flushing. Modification of the taste of alcoholic beverages has also been reported. Metronidazole should not be used if you are taking Disulfiram (used to maintain abstinence from alcohol), because the combination can cause confusion and psychotic reactions.
  • People taking oral anticoagulant (blood-thinning) drugs such as Warfarin will have to have their dose reduced because Metronidazole increases the effect of anticoagulants.
  • Metronidazole raises Lithium blood levels, effects, and toxicity.
  • Cimetidine can interfere with the liver’s ability to break down Metronidazole, causing increased amounts of Metronidazole in your blood. Your Metronidazole dosage may have to be reduced if you are taking Cimetidine.
  • Phenobarbital and other barbiturates Can increase the rate at which Metronidazole is broken down, compromising its effectiveness.
  • Drugs that cause nervous-system toxicity – such as Mexiletine, Ethambutol, Isoniazid, Lindane, Lincomycin, Lithium, Pemoline, Quinacrine, and long-term high-dose vitamin B6 (Pyridoxine) – should not be taken with Metronidazole because nervous-system effects may be increased.
  • Metronidazole may increase blood levels of Phenytoin by interfering with its breakdown in the liver. This could increase the risk of Phenytoin side effects and might result in the need to adjust your Phenytoin dosage.

Food Interactions of Generic Flagyl

This drug is best taken with food to avoid stomach upset.

Usual Dose

Adult: for the treatment of amoebic dysentery, 500 to 750 mg 3 times per day for 5 to 10 days. For trichomonal infections, 250 mg 3 times per day for 7 days, or 2 grams in 1 dose.


Single doses as large as 15,000 mg have been taken in suicide attempts and accidental doses. Overdose symptoms include nausea, vomiting, clumsiness and unsteadiness, seizures, and pain or tingling in the hands or feet. Call your local poison control center for more information. ALWAYS bring the medicine bottle if you go for treatment.

Special Information

Call your doctor if you become dizzy or light-headed while taking this drug, or if you develop numbness, tingling, pain, or weakness in your hands or feet, or seizures (with high doses of Metronidazole). Rare side effects that demand your doctor’s attention include clumsiness or unsteadiness; mood changes; unusual vaginal irritation, discharge, or dryness; skin rash, hives, or itching; or severe pain of the back or abdomen accompanied by vomiting, appetite loss, or nausea. Call your doctor if other side effects become particularly bothersome or persistent.

Metronidazole may cause darkening of your urine; this is probably not important, but inform your doctor if this happens.

Follow your doctor’s dosage instructions faithfully and don’t stop until the full course of therapy has been taken.

Metronidazole may cause dry mouth, which usually can be relieved with ice, hard candy, or gum. Call your doctor or dentist if dry mouth persists for more than 2 weeks.

If you forget to take a dose of Metronidazole, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not take a double dose.

Special Populations


Metronidazole passes into the fetal blood circulation soon after it is taken. This drug should not be taken during the first 3 months of pregnancy and should be used with caution during the last 6 months.

About the same amount of Metronidazole passes into breast milk as is in the mother’s blood. Breast-feeding while taking this drug may cause side effects in your infant. If you must take Metronidazole, bottle-feed your baby. After you have finished your treatment, express any milk produced while you were taking the drug and discard it plus any pumped breast milk you might have saved. Nursing can be resumed 1 or 2 days after stopping Metronidazole.


Seniors, particularly those with advanced liver disease, are more sensitive to the effects of this drug and may require less medicine. Follow your doctor’s directions and report any side effects at once.



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