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Flagyl ER (Generic Metronidazole)

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In laboratory animals, metronidazole can result in cancer. Discuss the advantages and disadvantages of using this medicine with your doctor.

Why is this medication prescribed?

The gastrointestinal (GI) tract, skin, heart, bone, joints, lungs, blood, neurological system, and other parts of the body are among the systems that are treated with metronidazole pills and capsules. The treatment of STDs with metronidazole pills and capsules is another usage. Women who have bacterial vaginosis, an infection brought on by having an excessive amount of specific dangerous bacteria in the vagina, can be treated with metronidazole extended-release (long-acting) pills. Metronidazole is a member of the nitroimidazole antimicrobials drug class. It functions by halting bacterial growth.

The flu, the common cold, or any other viral diseases cannot be treated with antibiotics. Antibiotic overuse increases your risk of developing a subsequent infection that is resistant to antibiotic therapy.

How should this medicine be used?

Metronidazole is available as an oral capsule, an extended-release tablet, and a tablet. The usual dosage for metronidazole capsules and tablets is one dose (or two doses on the same day), or two to four times daily for up to 10 days or longer. Extended-release metronidazole pills are typically given once daily for seven days, at least an hour before or two hours after a meal. Ask your doctor or pharmacist to explain any instructions on your prescription label that you do not understand, and carefully follow their instructions. Administer metronidazole precisely as prescribed. Never take it in quantities or frequencies other than those recommended by your doctor.

Do not split, chew, or crush the extended-release pills; instead, swallow them whole.

Even if you feel better, keep taking this medication. Without first consulting your doctor, do not discontinue taking it. Your infection could not be entirely healed if you stop taking this drug too soon or skip doses, and the bacteria might develop an antibiotic resistance.

Other uses for this medicine

For the treatment of bacterial vaginosis in women, metronidazole pills are utilized.

Ask your doctor or pharmacist for more details if you believe this drug should be used for something else.

What special precautions should I follow?

Before taking metronidazole,

  • If you have an allergy to metronidazole, secnidazole (Solosec), tinidazole (Tindamax), any other drugs, or any of the chemicals in preparations for taking metronidazole, let your doctor and pharmacist know right once. Request a list of the components from your pharmacist.
  • If you use or have used disulfiram (Antabuse), let your doctor know. In the event that you are now taking disulfiram or have recently taken it, your doctor may advise against using metronidazole.
  • Inform your doctor and pharmacist about any prescription and over-the-counter drugs, vitamins, herbal items, and nutritional supplements you are now taking or intend to take. Incorporate any of the following: Warfarin (Coumadin, Jantoven), busulfan (Busulfex, Myleran), cimetidine (Tagamet HB), lithium (Lithobid), phenobarbital, and phenytoin (Dilantin, Phenytek) are anticoagulants (sometimes known as “blood thinners”).
  • Inform your doctor if you have Crohn’s disease, blood, kidney, or liver illness now or ever had any of these conditions.
  • Inform your physician if you are nursing a baby, intend to get pregnant, or are already pregnant. Call your doctor if you become pregnant while taking metronidazole. Metronidazole should normally not be taken by pregnant women during the first trimester (the first 3 months of pregnancy).
  • Avoid consuming alcoholic beverages and using products that contain alcohol or propylene glycol while taking this medication and for at least 3 days following your last dose. When combined with metronidazole, alcohol and propylene glycol can make you sick to your stomach, make you throw up, give you headaches, make you sweat, and make your face red.

What should I do if I forget a dose?

If you miss a dosage, take it as soon as you recall. If the next dose is soon due, skip the missed one and carry on with your regular dosing plan. To make up for a missing dose, do not take a second one.

What side effects can this medication cause?

There may be negative effects from metronidazole. If any of these symptoms are severe or do not go away, let your doctor know right once:

  • Vomiting
  • Nausea
  • Diarrhea
  • Constipation
  • Uneasy stomach
  • Stomach pain
  • Reduced appetite
  • Headache
  • Mouth ache
  • Harsh, unpleasant metallic flavor
  • Tongue that is hairy; mouth or tongue inflammation

Some adverse effects can be very harmful. Call your doctor right away if you have any of the following symptoms:

  • Tingling, burning, or numbness in your feet or hands
  • Seizures
  • Rash
  • itching
  • Hives
  • Blistered or flaking skin
  • flushing
  • Fever, sore throat, stuffy nose, or other infection-related symptoms
  • Joints hurt
  • Dizziness
  • Having trouble speaking
  • Difficulty coordinating
  • Confusion
  • Agitation

Other negative effects of metronidazole are possible. If you experience any strange issues while taking this medicine, contact your doctor right away.

You or your doctor can submit a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online at or by phone at 1-800-332-1088 if you have a serious side event.

What should I know about storage and disposal of this medication?

Keep this medication tightly closed in the original container and out of the reach of children. Keep it at room temperature and out of the bathroom and away from light, excessive heat, and moisture.

As many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and are simple for young children to open, it is crucial to keep all medications out of sight and out of reach of children. Always lock safety caps and promptly stash medication up and away from young children where it is out of their sight and reach to prevent poisoning.

Unused prescriptions must be disposed of carefully to prevent pets, kids, and other people from ingesting them. You should not, however, dispose of this medication in the toilet. Instead, utilizing a medicine take-back program is the easiest approach to get rid of your medication. To find out about take-back programs in your area, speak with your pharmacist or the garbage/recycling department in your city. If you do not have access to a take-back program, see the FDA’s Safe Disposal of Medicines website at for additional information.

In case of emergency/overdose

Call the poison control hotline at 1-800-222-1222 in the event of an overdose. Additionally, information can be found online at Call 911 right once if the person has collapsed, experienced a seizure, is having difficulty breathing, or cannot be roused.

Overdose signs could include the following:

  • Nausea
  • Vomiting
  • Muscular coordination loss
  • Tingling, burning, or numbness in your feet or hands
  • Seizures

What other information should I know?

Maintain all scheduled times with your physician and the lab. To determine how you are responding to metronidazole, your doctor may perform a few lab tests.

Inform your doctor and the laboratory staff that you are taking metronidazole prior to any laboratory test.

No one else should take your medication. It’s likely that your prescription cannot be renewed. Call your doctor if you continue to experience infection symptoms after finishing the metronidazole.

You should keep a written record of every medication you take, including any over-the-counter (OTC) items, prescription drugs, and dietary supplements like vitamins and minerals. This list should be brought with you whenever you see a doctor or are admitted to the hospital. You should always have this information with you in case of emergencies.

Brand names

  • Flagyl®
  • Flagyl® 375
  • Flagyl® ER
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