What is metronidazole?

Metronidazole is an antibiotic that may be used to treat certain infections of the vagina, stomach, liver, skin, joints, brain and spinal cord, lungs, heart, or bloodstream.

Metronidazole has been approved to treat:

• Symptomatic trichomoniasis (a sexually transmitted infection) in adults that has been confirmed by culture or wet smear test
• Asymptomatic trichomoniasis in females when associated with cervical changes, and in asymptomatic sexual partners
• Amebiasis (an infection caused by a parasite) in adults and children
• Anaerobic bacterial infections (infections caused by bacteria that do not need oxygen to survive).

Metronidazole is thought to work by first diffusing into the cytoplasm of the anaerobic bacteria where it is then activated and reduced into a short-lived nitroso free radical which can interact with DNA, causing a loss of the helical DNA structure, strand breakage, and bacterial death.

Metronidazole is well absorbed after oral administration, with peak concentrations being reached in one to two hours. Although it starts to work quickly, it may take a couple of days before you start to feel better or notice an improvement in your symptoms. It is important that you still finish the course of metronidazole that your doctor has prescribed, even if you feel better, because the infection may still be present, and it could flare up or recur if you haven’t finished the course.

Metronidazole was first FDA-approved in 1963.

Warnings

To reduce the development of drug-resistant bacteria, do not use metronidazole to treat any condition that has not been checked by your doctor. This medicine will not treat a viral infection such as the common cold or flu.

Metronidazole has been shown to be carcinogenic in rats and mice and unnecessary use should be avoided.

Do not use metronidazole if you recently drank alcohol, or have taken disulfiram (Antabuse) within the past 2 weeks. Do not drink alcohol or consume foods or medicines that contain propylene glycol while you are taking metronidazole and for at least 3 days after you stop taking it.

Seizures and other nervous system abnormalities have been reported in patients treated with metronidazole. You should stop using this medicine immediately if you experience any neurological symptoms such as seizures, headaches, visual changes, weakness, numbness, or tingling.

Before taking this medicine

You should not use this medicine if you are allergic to metronidazole, secnidazole, or tinidazole, or if you:

• drank alcohol in the past 3 days
• consumed foods or medicines that contain propylene glycol in the past 3 days or
• took disulfiram (Antabuse) within the past 14 days
• have Cockayne Syndrome (a rare genetic disorder that affects growth and development).

Before taking metronidazole, tell your healthcare provider about all of your medical conditions, including if you:

• liver disease
• kidney disease (or if you are on dialysis)
• a heart rhythm disorder
• a stomach or intestinal disease such as Crohn’s disease
• a blood cell disorder such as anemia (lack of red blood cells) or low white blood cell (WBC) counts
• medical problems that affect the brain or a nerve disorder
• a yeast infection or a fungal infection anywhere in your body
• a history of blood problems
• or take any medications, especially warfarin, lithium, busulfan, cimetidine, phenytoin, or phenobarbital.

Tell your doctor if you are pregnant or intend to become pregnant. The use of metronidazole during pregnancy has been well-studied and a review of 17 studies found that treating bacterial vaginosis and trichomoniasis with metronidazole reduced the risk of preterm birth and was effective and offered no teratogen risk. Conversely, isolated studies have suggested its use may result in low birth weight or preterm delivery. Talk to your doctor about the risks and benefits of taking metronidazole during pregnancy. Some product labels for metronidazole say it is contraindicated during the first trimester.

Tell your doctor if you are breastfeeding or plan to breastfeed. Metronidazole can pass into your breast milk. Talk to your healthcare provider about the best way to feed your baby while taking metronidazole. If you are breastfeeding, you may consider pumping and throwing away your breast milk during treatment with metronidazole and for 48 hours after your last dose and feeding your infant stored human milk or formula.

Not all uses of metronidazole are approved for treating children and teenagers. Metronidazole is not approved to treat vaginal infections in girls who have not begun having menstrual periods.

How should I take metronidazole?

Take metronidazole exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

• The dose depends on the infection being treated.
• The dosage should be reduced by 50% in those with severe hepatic impairment.
• In patients undergoing hemodialysis, consider a supplementary dose following the hemodialysis session, depending on the patient’s clinical situation.
• Metronidazole will not treat a vaginal yeast infection. You may even develop a new vaginal yeast infection, which may need to be treated with antifungal medication. Tell your doctor if you have symptoms such as itching or discharge during or after treatment with this medicine.
• If you are treating a vaginal anaerobic bacterial infection, your sexual partner may also need to take metronidazole so you don’t become reinfected.
• Do not share this medicine with another person, even if they have the same symptoms you have.
• Metronidazole is usually given for up to 10 days in a row. You may need to repeat this dosage several weeks later.
• Keep using this medicine even if your symptoms quickly improve. Skipping doses could make your infection resistant to medication. This medicine will not treat a viral infection (flu or a common cold).

Oral metronidazole

• Oral metronidazole tablets, capsules, and the suspension are taken by mouth. May be taken with or without food.
• Shake the oral suspension well before each use. Always use an accurate measuring device to measure the correct amount. Do not use a household teaspoon or tablespoon to measure your medicine. You can ask your pharmacist for the measuring device you should use and how to measure the correct dose.
• Swallow the extended-release tablet whole and do not crush, chew, or break it.

Metronidazole injection

• The injection is given as an infusion into a vein. A healthcare provider will give you the injection if you are unable to take the medicine by mouth.

Dosing information

Trichomoniasis (adults)

Treatment should be individualized. Usual dosages are:

• One-day treatment: 2 grams as a single oral dose or a split dose given on the same day
• 7-day course: 250mg three times daily for 7 consecutive days.

Amebiasis

• Adults: acute amebic dysentery. 750mg three times daily for 5 to 10 days.
• Adults: amebic liver abscess. 500mg or 750mg three times daily for 5 to 10 days.
• Children: 35mg/kg/24 hours to 50mg/kg/24 hours divided into three doses daily for 10 days.

Do not exceed adult dosages.

Anaerobic Bacterial Infections (adults)

For more serious anaerobic infections, intravenous metronidazole is usually administered initially.

• Adults: 7.5 mg/kg every 6 hours (this works out at approximately 500mg for a 70kg adult) orally for 7 to 10 days. Maximum dose 4g/24 hours.

A longer course of treatment may be required for bone, joint, lower respiratory tract, and endocardium infections.

What should I avoid while using metronidazole?

Do not drink alcohol or consume foods, medicines, or other products that contain alcohol or propylene glycol while taking metronidazole and for 3 days after your last dose. You may have unpleasant effects such as headaches, nausea, vomiting, stomach cramps, and warmth or tingling under your skin.

What are the side effects of metronidazole?

Get emergency medical help if you have signs of an allergic reaction to metronidazole (hives, itching, warmth, or tingling; fever, joint pain; dry mouth, dry vagina; stuffy nose, difficulty breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Metronidazole may cause serious side effects including:

• Nervous system problems, including brain disorder (encephalopathy), inflammation of the brain and spinal cord membranes (aseptic meningitis), numbness or tingling in the hands or feet (peripheral neuropathy), and seizures (convulsions). Tell your healthcare provider right away if you have any nervous system problems while taking metronidazole
• Worsening yeast infection (candidiasis) symptoms in people with a known yeast infection or a yeast infection they were not aware of
• Low white blood cell count (leukopenia) in people with a history of blood problems. This can affect how well the body fights infection.

The most common side effects of metronidazole include

• Diarrhea
• Nausea
• Headache
• Pain in the upper abdomen and abdominal cramping
• Vomiting
• Weight loss
• Constipation

What is nitazoxanide?

Nitazoxanide is an antiprotozoal medicine that treats infections caused by protozoa (single-cell parasites that live in moist places such as lakes, streams, and soil).

Nitazoxanide is used to treat diarrhea caused by Giardia or Cryptosporidium. These conditions are sometimes called “Traveler’s diarrhea.” Nitazoxanide is used in adults and children who are at least 1 year old.

Nitazoxanide may also be used for purposes not listed in this medication guide.

Nitazoxanide side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Common side effects of nitazoxanide may include:

• nausea, stomach pain;
• headache; or
• discolored urine.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

Warnings

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Before taking this medicine

You should not use nitazoxanide if you are allergic to it.

To make sure nitazoxanide is safe for you, tell your doctor if you have:

• liver or kidney disease;
• HIV or AIDS; or
• a weak immune system.

The tablet form of nitazoxanide should not be given to a child younger than 12 years old. Children ages 1 to 11 years should use only the oral suspension (liquid) form of nitazoxanide.

Nitazoxanide is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant.

It is not known whether nitazoxanide passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

How should I take nitazoxanide?

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Take nitazoxanide with food.

Nitazoxanide is usually taken once every 12 hours for 3 days. Follow your doctor’s dosing instructions very carefully.

Shake the oral suspension (liquid) well just before you measure a dose. Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

Store at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use. Throw away any unused liquid after 7 days.

Nitazoxanide dosing information

Usual Adult Dose for Cryptosporidiosis:

500 mg orally every 12 hours for 3 days

Use: For the treatment of diarrhea due to Giardia lamblia or Cryptosporidium parvum

Usual Adult Dose for Giardiasis:

500 mg orally every 12 hours for 3 days

Use: For the treatment of diarrhea due to Giardia lamblia or Cryptosporidium parvum

Usual Pediatric Dose for Cryptosporidiosis:

1 to 3 years: 100 mg orally every 12 hours
4 to 11 years: 200 mg orally every 12 hours
12 years or older: 500 mg orally every 12 hours

Duration of Therapy: 3 days

Use: For the treatment of diarrhea due to G lamblia or C parvum

Usual Pediatric Dose for Giardiasis:

1 to 3 years: 100 mg orally every 12 hours
4 to 11 years: 200 mg orally every 12 hours
12 years or older: 500 mg orally every 12 hours

Duration of Therapy: 3 days

Use: For the treatment of diarrhea due to G lamblia or C parvum

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line .

What should I avoid while taking nitazoxanide?

Follow your doctor’s instructions about any restrictions on food, beverages, or activity.

What other drugs will affect nitazoxanide?

Other drugs may interact with nitazoxanide, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.