What is metronidazole used for?

Metronidazole is a generic medication that’s often used to treat infections caused by bacteria, parasites, and other organisms called protozoa. Infections caused by these organisms include:

• sexually transmitted diseases (STDs)
  • trichomoniasis
  • pelvic inflammatory disease (PID)
• bacterial vaginosis
• skin infections like rosacea
• gastrointestinal infections
• anaerobic bacterial infections (these infections can happen when certain tissues are injured or exposed due to surgery or something like an animal bite)
  • gum disease
  • sinusitis
  • appendicitis
  • tetanus
  • infected wounds

Metronidazole kills the bacteria, parasites, or other organisms that are causing the infection.

Metronidazole comes in the following forms:

• lotion
• topical cream
• topical gel
• solution for injection
• oral forms
  • immediate-release tablets
  • extended-release tablets
  • oral capsules

Immediate-release drugs are released into the body right away. Extended-release drugs are released into the body slowly over time. The oral tablets also come in a brand-name version called Flagyl.

How metronidazole is used to treat STDs

Metronidazole is used to treat certain STDs like trichomoniasis.

Trichomoniasis, sometimes called “trich”, is common in the United States, affecting about 2 million people. Most people with trichomoniasis do not experience any symptoms. Those who do have symptoms may experience unusual discharge from the genitals, burning or itching of the genitals, and a frequent urge to urinate.

To treat trichomoniasis, you doctor will typically prescribe 2 grams (g) of metronidazole tablets, either as a single dose or in two divided doses of 1 gram each, taken in the same day. Alternatively, they may prescribe 250 milligrams (mg) taken 3 times daily for 7 consecutive days. It’s important to talk with your doctor or pharmacist to understand what dosage is right for you.

Some people may confuse trichomoniasis with a urinary tract infection (UTI), but these are two different conditions. Bacteria cause UTIs, and parasites cause trichomoniasis. Metrotinidazole is not commonly used to treat UTIs.

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How it’s used for gastrointestinal infections and diarrhea

Amebiasis is a condition that affects the gastrointestinal tract, which includes the stomach and intestines.

Amebiasis is a parasitic infection caused by an amoeba or parasite. This parasite usually enters the body when a person ingests contaminated food or water or through contact with fecal matter. Most people with amebiasis won’t experience symptoms. But symptoms may include:

• loose stool
• diarrhea
• stomach pain and cramping

To treat amebiasis, doctors typically prescribe the following doses of metronidazole:

• 500 or 750 mg oral tablet, three times per day for 5 to 10 days
• 750 mg oral capsules, three times per day for 5 to 10 days

Metronidazole may also be prescribed for gastrointestinal infections in dogs. Veterinarians may prescribe it off-label to treat conditions like giardia and inflammatory bowel disease in dogs. Off-label use is when a drug is prescribed for a purpose other than what it’s approved for. It’s important to talk with your veterinarian to find out more about metronidazole before using this medication for a dog.

How metronidazole is used to treat PID and bacterial vaginosis

Metronidazole is often used to treat reproductive system disorders like pelvic inflammatory disease (PID) and bacterial vaginosis in females.

Sex and gender exist on spectrums. In this article, we use the terms “female” and “male” to refer to a person’s sex assigned at birth.

PID is an infection of the reproductive system that often develops because of a sexually transmitted infection (STI) like gonorrhea or chlamydia. A lot of people do not experience symptoms. But symptoms may include:

• pain around the pelvic area
• pain when having sex or peeing
• heavy or painful periods
• unusual discharge

A doctor may prescribe metronidazole as part of combination therapy for PID. This means you may need to take it with other medications, such as doxycycline, ceftriaxone, or cefoxitin.

Bacterial vaginosis develops when certain types of bacteria are present in higher amounts than usual. Your vagina naturally contains a delicate balance of different kinds of bacteria. Using douches or vaginal washes, having multiple sexual partners, or having sex without using condoms or dental dams may throw off the balance of the bacteria.

Anyone can develop bacterial vaginosis. It doesn’t always cause symptoms, but some people may experience:

• gray or white, fishy-smelling vaginal discharge
• itching or pain in the vulva
• pain or burning when urinating

The recommended dosage of metronidazole for bacterial vaginosis is:

• 500 mg taken orally twice a day for 7 days
• metronidazole gel
  • one full applicator (5 g) of metronidazole 0.75% gel applied intravaginally once a day for 5 days OR
  • a single dose consisting of one full applicator (5 g) of metronidazole 1.3% gel applied intravaginally one time

Make sure you talk with your doctor or pharmacist to understand what dosage is right for you.

How it’s used for anaerobic bacterial infections

Anaerobic bacteria cause anaerobic bacterial infections. These bacteria occur naturally in the body, but infections can happen when certain tissues are injured or exposed due to surgery or something like an animal bite.

Examples of anaerobic bacterial infections include:

• appendicitis
• abscess in the brain, abdomen, lung, or liver
• sinus infection
• tetanus
• pneumonia
• gum disease

Doctors typically prescribe 7.5 mg of metronidazole per kilogram (kg) of body weight, taken every six hours for 7 to 10 days. For reference, 1 kg is equal to about 2.2 pounds. For a more complicated infection, your doctor may recommend you continue treatment for a longer period of time. The maximum metronidazole dosage is 4,000 mg (4 g) in 24 hours.

Side effects

Always take Metronidazole exactly as your doctor prescribes. This is because metronidazole can cause some side effects. Tell your doctor or pharmacist if you have side effects that don’t go away or become bothersome.

Some of the more common side effects of metronidazole include:

• nausea or vomiting
• headache
• loss of appetite
• diarrhea
• metallic taste
• irritation or inflammation in the vagina
• itchy skin

Summary

Metronidazole is a prescription antimicrobial drug that is used to treat certain infections caused by bacteria or parasites. Thesr include certain STDs, PID, bacterial vaginosis, rosacea, gastrointestinal infections, and anaerobic infections like gum disease, sinusitis, appendicitis, and tetanus. 

This medication comes in different forms. The form and dosage will vary depending on what condition you are taking it for and the severity of your symptoms.

Metronidazole can cause some side effects, such as nausea, headache, diarrhea, appetite loss, and metallic taste.

Talk with your doctor to learn more about the uses and possible side effects of metronidazole.

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