- Bacterial Infections 101 Pictures Slideshow
- Take the Tummy Trouble Quiz
- Hepatitis C Slideshow Pictures
- What is metronidazole (Flagyl, Flagyl ER), and how does it work?
- What brand names are available for metronidazole?
- Is this drug available as a generic?
- Do I need a prescription for this drug?
- Why is metronidazole prescribed to patients?
- What are the side effects of metronidazole?
- What is the dosage for metronidazole, and how do I take it?
- Which drugs or supplements interact with this medication?
- Is this drug safe to use during pregnancy or while breastfeeding?
- What else should I know about Flagyl (metronidazole)?
What is metronidazole (Flagyl, Flagyl ER), and how does it work?
Flagyl is an antibiotic effective against anaerobic bacteria and certain parasites. Anaerobic bacteria are single-celled, living organisms that thrive in environments in which there is little oxygen (anaerobic environments). Anaerobic bacteria can cause disease in the abdomen (bacterial peritonitis), liver (liver abscess), and pelvis (abscess of the ovaries and the Fallopian tubes). Giardia lamblia and ameba are intestinal parasites that can cause abdominal pain and diarrhea in infected individuals. Trichomonas is a vaginal parasite that causes inflammation of the vagina (vaginitis). Metronidazole selectively blocks some of the functions within the bacterial cells and the parasites resulting in their death.
What brand names are available for metronidazole?
- Flagyl and Flagyl ER are the available brand names for metronidazole in the US.
- Metro IV, Metromidol, Protostat, and Satric are brands names for metronidazole that have been discontinued in the US.
Why is metronidazole prescribed to patients?
- Flagyl is used to treat parasitic infections including Giardia infections of the small intestine, amebic liver abscess, and amebic dysentery (infection of the colon causing bloody diarrhea), bacterial vaginosis, trichomonas vaginal infections, and carriers of trichomonas (both sexual partners) who do not have symptoms of infection.
- Flagyl is also used alone or in combination with other antibiotics in treating abscesses in the liver, pelvis, abdomen, and brain caused by susceptible anaerobic bacteria.
- Flagyl is also used in treating infection of the colon caused by a bacterium called C. difficile. Many commonly-used antibiotics can alter the type of bacteria that inhabit the colon. C. difficile is an anaerobic bacterium that can infect the colon when the normal types of bacteria in the colon are inhibited by common antibiotics. This leads to inflammation of the colon (pseudomembranous colitis) with severe diarrhea and abdominal pain.)
- Flagyl also is used in combination with other drugs to treat Helicobacter pylori (H. pylori) that causes stomach or intestinal ulcers.
- Flagyl topical gel is used for treating acne rosacea.
- Flagyl vaginal gel is used for treating bacterial vaginosis.
What are the side effects of metronidazole?
Flagyl is a useful antibiotic and is generally well tolerated with appropriate use.
The most common and minor side effects include:
- Loss of appetite
- A metallic taste
- Rarely a rash
- Abdominal cramps
- Dry mouth
- Dark-colored urine
- Metallic taste in mouth
- Weight loss (anorexia)
- Furry tongue
- Nasal congestion
- Vaginal dryness
Side effects that are uncomfortable, but may become serious include:
- Brain disease
- Mouth sores
- Pain with urination
- Prickling or tingling sensations that may become permanent
- Pelvic pain or pressure
- Decrease of libido
Serious side effects of Flagyl are rare and the drug should be stopped if these symptoms appear:
Latest Digestion News
Daily Health News
What is the dosage for metronidazole, and how do I take it?
- Metronidazole may be taken orally with or without food.
- In the hospital, metronidazole can be administered intravenously to treat serious infections.
- The liver is primarily responsible for eliminating metronidazole from the body, and doses may need to be reduced in patients with liver disease and abnormal liver function.
Various metronidazole regimens are used. Some examples are listed below.
- Amebic dysentery: 750 mg orally 3 times daily for 5-10 days
- Amebic liver abscess: 500-750 mg orally three times daily for 5-10 days
- Anaerobic infections: 7.5 mg/kg orally or by injection every 6 hours for 7 to 10 days not to exceed 4 grams daily.
- Bacterial vaginosis: 750 mg (extended release tablets) once daily for 7 days or 500 mg twice daily for 7 days or 2 g single dose or one applicator-full of 0.75% vaginal gel, once or twice daily for 5 days.
- Clostridium difficile infection: 250-500 mg orally 4 times daily or 500-750 orally 3 times daily
- Giardia: 250 mg orally three times daily for 5 days Helicobacter pylori: 800-1500 mg orally daily for several days in combination with other drugs.
- Pelvic inflammatory disease (PID): 500 mg orally twice daily for 14 days in combination with other drugs.
- Trichomoniasis: 2 g single dose or 1 g twice
- Rosacea: apply topical gel 0.75-1% once daily
Which drugs or supplements interact with this medication?
- Alcohol should be avoided because metronidazole and alcohol together can cause severe nausea, vomiting, cramps, flushing, and headache.
- Metronidazole can increase the blood thinning effects of warfarin (Coumadin, Jantoven) and increase the risk of bleeding probably by reducing the breakdown of warfarin.
- Cimetidine (Tagamet) increases blood levels of metronidazole while cholestyramine (Questran, Questran Light) reduces blood levels of metronidazole by reducing its absorption.
- Metronidazole should not be combined with amprenavir (Agenerase) for treating human immunodeficiency disease (infection with HIV) because amprenavir contains propylene glycol.
- Metronidazole blocks the breakdown of propylene glycol in the liver leading to accumulation of propylene glycol in blood. Accumulation of propylene glycol could cause seizures, increased heart rate, and lead to kidney failure.
- Metronidazole increases the blood levels of carbamazepine (Tegretol, Tegretol XR, Equetro, Carbatrol), lithium (Eskalith, Lithobid) and cyclosporine though unknown mechanisms. Serious reactions may occur if these drugs are taken with metronidazole.
Is this drug safe to use during pregnancy or while breastfeeding?
What else should I know about Flagyl (metronidazole)?
What preparations of Flagyl (metronidazole) are available?
- Tablets: 250 and 500 mg.
- Tablets, extended release: 750 mg.
- Capsule: 375 mg.
- Cream: 0.75% and 1%.
- Lotion: 0.75%.
- Gel: 0.75% and 1%.
- Injection: 5 mg/ml
How should I keep Flagyl (metronidazole) stored?
- Metronidazole should be stored at room temperature and protected from light.
When was metronidazole approved by the FDA?
- The FDA approved metronidazole tablets in July 1963.
Subscribe to MedicineNet's General Health Newsletter
Metronidazole (Flagyl, Flagyl ER) is a prescription antibiotic medication prescribed for the treatment of a variety of parasitic and bacterial infections of the vagina, gynecological area, skin, intra-abdominal cavity, blood, bone, joint, nervous system, and heart. For example:
- Bacterial vaginosis
- Pelvic inflammatory disease (PID)
- C. difficile
- H. pylori
- STDs (trichomonas)
- Acne rosacea
- Tubo-ovarian abscess
- Bacterial septicemia
- Brain abscess
- Lung abscess
Research has shown that Flagyl causes cancer in mice and rats. Only take this drug as your doctor prescribes it. This medicine is an antibacterial drug and is susceptible to antibiotic resistance; a healthcare provider should only prescribe it for treatment if the infection is proven or strongly thought to be caused by bacteria.
Common side effects of Flagyl are loss of appetite, headaches, and nausea. Serious side effects are encephalopathy, seizures, and aseptic meningitis. You can take metronidazole taken with or without food. Avoid drinking alcohol while taking this drug because the combination can cause severe nausea, vomiting, headache, flushing, and cramps.
Flagyl is available in doses for adults as tablets of 250 mg, 500 mg, and 750 mg. The dose for pediatric patients is available as tablets of 35 to 50 mg/kg/24 hours. Patient dosage administration depends upon the severity of infection caused by parasites or bacteria, and any other existing medical conditions, particularly if they are severe. There are several drug interactions with Flagyl. Interactions, for example, like warfarin (Coumadin, Jantoven), cimetidine (Tagamet), cholestyramine (Questran, Questran Light), amprenavir (Agenerase), lithium (Eskalith, Lithobid), and cyclosporine. This medicine may cause increased heart rate, which can lead to seizures. Ask your doctor, pharmacist, or other medical professional if you have questions about Flagyl.
Metronidazole also is available as a capsule (375 mg), cream (0.75% and 1 mg), Lotion (0.75%), gel (0.75% and 1%), and injection (5mg/ml).
Multimedia: Slideshows, Images & Quizzes
Bacterial Infections 101: Types, Symptoms, and Treatments
Learn more about bacteria and the most common bacterial infections. Get more information on bacterial skin infections, which...
Diverticulitis (Diverticulosis) Symptoms, Diet, Treatment
Diverticulitis (diverticulosis) is a condition in which the diverticulum or diverticula rupture in the colon causing infection....
Inflammatory Bowel Disease (IBD) Causes, Symptoms, Treatment
What is inflammatory bowel disease? IBD can include Crohn's disease and ulcerative colitis. Learn more about testing, treatments,...
Acne (Pimples) Quiz: Test Your Medical IQ
Acne is the most common skin disorder in the world. If you suffer from acne, you are not alone and many treatment options are...
Crohn's Disease Quiz
What causes Crohn's disease? What are the symptoms of Crohn's disease? How is Crohn's treated? Take this quiz to get the facts...
Chronic Fatigue Syndrome Quiz: Symptoms & Treatment
Exhausted all the time? Maybe it's not all in the mind. Take the Chronic Fatigue Syndrome (CFS) Quiz to learn more about tricky...
Crohn's Disease Causes, Symptoms, Diet
What is Crohn's disease? Get more information on this digestive disorder and how Crohn's can affect your diet. Learn more about...
Adult Acne (Pimples) Causes and Treatments
Acne (pimples) is a skin condition that blocks pores. Get answers on causes, solutions and treatments for this skin condition...
Picture of Trichomoniasis
Infection with trichomonas, in humans with Trichomonas vaginalis. See a picture of Trichomoniasis and learn more about the health...
Picture of Folliculitis
An infection of the hair follicles of the skin. See a picture of Folliculitis and learn more about the health topic.
Picture of Erythematous Deep Acne Scars
Acne scarring is a common sequel of severe inflammatory or cystic acne. It can present in a mild or cosmetically disfiguring...
Picture of Acne Vulgaris Nodulocystic
Inflammatory nodules, cysts, and pustules (left). See a picture of Acne Vulgaris Nodulocystic and learn more about the health...
Picture of Diverticulitis
Diverticula can be seen via barium x-ray (barium enema). See a picture of Diverticulitis and learn more about the health topic.
Picture of Diverticulosis
Diverticulosis is a condition where a patient has diverticula in the colon. See a picture of Diverticulosis and learn more about...
Picture of Cystic Acne
Cystic acne is a type of abscess that is formed when oil ducts become clogged and infected. See a picture of Cystic Acne and...
Picture of Peptic Ulcer
A hole in the lining of the stomach, duodenum, or esophagus. See a picture of Peptic Ulcer and learn more about the health topic.
Picture of Acne
Exactly what causes acne? Acne develops when cells and natural oils begin to block up tiny hair follicles in the skin. See a...
Picture of Baby Acne
Pink pimples ("neonatal acne") are often caused by exposure in the womb to maternal hormones. See a picture of Baby Acne and...
Chronic Fatigue Syndrome (CFS) Symptoms and Diagnosis
Chronic fatigue syndrome (CFS) can occur at any age for men or women. Learn more about the causes of chronic fatigue syndrome...
Acne 101: Types, Best Treatments, Medication, Cystic Acne
What is the best treatment for acne vulgaris? Can food choices influence acne? How can you get rid of blackheads? Learn why it's...
Skin Health: 15 Tips for Clear Skin
Acne, pimples, zits and blemishes often appear on the face, back, chest, neck, and shoulders where skin has the most amount of...
Acne Care Pictures: Skin Care Dos and Don'ts
Explore quick acne cover-ups, dos and don'ts. See solutions on how to best handle pesky pimples and remedies to avoid.
Related Disease Conditions
Jock itch is an itchy red rash that appears in the groin area. The rash may be caused by a bacterial or fungal infection. People with diabetes and those who are obese are more susceptible to developing jock itch. Antifungal shampoos, creams, and pills may be needed to treat fungal jock itch. Bacterial jock itch may be treated with antibacterial soaps and topical and oral antibiotics.
Bacterial vaginosis is an abnormal vaginal condition with signs and symptoms of vaginal discharge, vaginal odor, and vaginal pain. Bacterial vaginosis results from an overgrowth of normal bacteria in the vagina. Although it may cause some disturbing symptoms (discharge and odor), it is not dangerous and cannot be passed by sex. Diagnosis becomes important to exclude serious infections like gonorrhea and Chlamydia. Many treatment options are available such as oral antibiotics and vaginal gels.
Acne is a localized skin inflammation as a result of overactivity of oil glands at the base of hair follicles. This inflammation, depending on its location, can take the form of a superficial pustule (contains pus), a pimple, a deeper cyst, congested pores, whiteheads, or blackheads. Treatments vary depending on the severity of the acne.
Diverticulitis (Diverticulosis, Diverticular Disease)
Most people with diverticulosis have few if any symptoms at all. When people do experience signs and symptoms of diverticulosis (diverticular disease) they may include abdominal pain, abdominal cramps, diarrhea, constipation, and bloating. Diverticulitis is a condition in which diverticuli in the colon rupture. The rupture results in infection in the tissues that surround the colon. Treatment methods for diverticulitis includes prescription medications, and in some cases, diverticulitis surgery.
Rosacea is a skin disease that causes redness of the forehead, chin, and lower half of the nose. In addition to inflammation of the facial skin, symptoms include dilation of the blood vessels and pimples (acne rosacea) in the middle third of the face. Oral and topical antibiotics are treatments for rosacea. If left untreated, rhinophyma (a disfiguring nose condition) may result.
Folliculitis is a skin condition that causes small red bumps to form around the hair follicles. Skin bacteria such as Staphylococcus and Pseudomonas may infect the follicles. Treatment involves over-the-counter bacterial washes, topical antibiotics, and/or topical steroids.
Is C. diff (Clostridium difficile) Contagious?
C. diff, or Clostridium difficile, is a bacteria that infects the colon. C. diff bacteria can be found on furniture, bathroom floors, telephones, fingernails, jewelry, toilet seats, and other places.Symptoms of C. diff infection are fever, abdominal pain, and cramps; however, not all people infected with C. diff have symptoms. Treatments for C. diff are antibiotics and surgery in some cases.
Peripheral neuropathy is a problem with the functioning of the nerves outside of the spinal cord. Symptoms may include numbness, weakness, burning pain (especially at night), and loss of reflexes. Possible causes may include carpel tunnel syndrome, shingles, vitamin or nutritional deficiencies, and illnesses like diabetes, syphilis, AIDS, and kidney failure. Peripheral neuropathy is diagnosed with exams and tests. Treatment for the condition depends on the cause. Usually, the prognosis for peripheral neuropathy is good if the cause can be successfully treated or prevented.
Peptic Ulcer (Stomach Ulcer)
Peptic or stomach ulcers are ulcers are an ulcer in the lining of the stomach, duodenum, or esophagus. Ulcer formation is related to H. pylori bacteria in the stomach, use of anti-inflammatory medications, and cigarette smoking. Symptoms of peptic or stomach ulcers include abdominal burning or hunger pain, indigestion, and abdominal discomfort after meals. Treatment for stomach ulcers depends upon the cause.
Amebiasis (Entamoeba Histolytica Infection)
Amebiasis is an infection caused by an amoeba. Signs and symptoms include bloody stools, abdominal pain, weight loss, fever, and gas. Treatment may involve taking luminal agents or antibiotics. Surgery may be indicated for various reasons.
H. pylori (Helicobacter Pylori) Infection
Helicobacter pylori (H. pylori) is a bacteria that causes chronic inflammation (gastritis) of the inner lining of the stomach, and also is the most common cause of ulcers worldwide. About 50% of people in the world carries or is infected with H. pylori. Common symptoms of H. pylori infection are occasional abdominal discomfort, bloating, belching or burping, and nausea and vomiting. H. pylori infection is difficult to eradicate, and treatment is with two or more antibiotics.
Vaginitis (Inflammation of the Vagina)
Vaginitis refers to inflammation of the vagina. Vaginitis can be caused by infections, menopause, or poor hygiene. Symptoms of vaginitis include vaginal itching, discharge, odor, pain, or discomfort. Treatment for vaginitis depends on the cause. Antibiotics may be necessary for some forms of vaginitis.
Crohn's disease is a chronic inflammatory disease, primarily involving the small and large intestine, but which can affect other parts of the digestive system as well. Abdominal pain, diarrhea, vomiting, fever, and weight loss are common symptoms.
Trichomoniasis is a sexually transmitted disease (STD) caused by a parasite passed from person to person. Trichomoniasis can be picked up from contact with damp, moist objects like towels, wet clothing, or toilet seat. Symptoms include yellow, green, or gray vaginal discharge with a strong odor, painful intercourse or urination, genital irritation and itching, and lower abdominal pain. Antibiotics are the only treatment to cure trichomoniasis.
SIBO (Small Intestinal Bacterial Overgrowth)
Small intestinal bacterial overgrowth (SIBO) refers to a condition in which abnormally large numbers of bacteria (at least 100,000 bacteria per ml of fluid) are present in the small intestine, but they are more like the bacteria that are found in the colon. There are many conditions associated with SIBO, including: Diabetes Scleroderma Crohn's disease Irritable bowel syndrome (IBS) It has been theorized that SIBO may be responsible for the symptoms of at least some patients with irritable bowel syndrome. Symptoms of SIBO include: Excess gas Abdominal bloating Abdominal pain Treatment for SIBO can include: Antibiotics Probiotics Low FODMAP Diet
Is H. pylori Contagious? Symptoms and Tests
H. pylori (Helicobacter pylori) infection: Is it contagious? H. pylori infection is caused by fecal contamination in either food or water, and by poor hygiene practices such as not washing the hands often. Common symptoms of H. pylori are a discomfort or pain in the area of the stomach. Some individuals describe the pain as gnawing or burning. Treatment of H. pylori infection is antibiotic therapy.
Clostridium Difficile Colitis (Antibiotic-Associated Colitis, C. difficile colitis)
Clostridium difficile (C. difficile) is a bacterium, and is one of the most common causes of infection of the colon. C. difficile spores are found frequently in hospitals, nursing homes, extended care facilities, and nurseries for newborn infants. They can be found: on bedpans, furniture, toilet seats, linens, telephones, stethoscopes, fingernails, rings, floors, infants' rooms, and diaper pails. They even can be carried by pets. Antibiotic-associated (C. difficile) colitis is an infection of the colon caused by C. difficile that occurs primarily among individuals who have been using antibiotics. Treatment for C. difficile colitis includes: hydration, replenishment of electrolyte deficiencies, discontinuing the antibiotic that caused the colitis, and using antibiotics to eradicate the C. difficile bacterium.
Crohn's Disease vs. Ulcerative Colitis (UC)
Crohn's disease and ulcerative colitis are diseases that cause inflammation of part of or the entire digestive tract (GI). Crohn's affects the entire GI tract (from the mouth to the anus), while ulcerative colitis or UC only affects the large and small intestine and ilium. Researchers do not know the exact cause of either disease. About 20% of people with Crohn's disease also have a family member with the disease. Researchers believe that certain factors may play a role in causing UC. Both Crohn's disease and ulcerative colitis are a type of inflammatory bowel disease, or IBD. Crohn's disease and ulcerative colitis both have similar symptoms and signs, for example, nausea, loss of appetite, fatigue, weight loss, episodic and/or persistent diarrhea, fever, abdominal pain and cramping, rectal bleeding, bloody stools, joint pain and soreness, eye redness, or pain. Symptoms unique to Crohn’s disease include anemia and skin changes. Symptoms of unique to ulcerative colitis include, certain rashes, an urgency to defecate (have a bowel movement). Doctors diagnose both diseases with similar tests and procedures. While there is no cure for either disease, doctors and other health care professionals can help you treat disease flares, and manage your Crohn's or UC with medication, diet, nutritional supplements, and/or surgery.
Giardiasis (Giardia lamblia) is a parasite responsible for a common form of infectious diarrhea. The parasite lives in two stages: trophozoites and cysts. People at risk for giardiasis are those that live in areas where there is inadequate sanitation or treatment of drinking water. Giardiasis also is a common cause of outbreaks of diarrhea in day-care centers. Symptoms of giardiasis include abdominal pain, stomach cramping, bloating, nausea, and fatigue. Treatment for giardiasis is with antibiotic medication.
Chronic Fatigue Syndrome (CFS or SEID)
Chronic fatigue syndrome (CFS) or systemic exertion intolerance disease (SEID) is a debilitating and complex disorder characterized by profound fatigue that lasts six months or longer, is not improved by bed rest, and may be worsened by physical or mental activity.
Inflammatory Bowel Disease (Intestinal Problems of IBD)
The inflammatory bowel diseases (IBD) are Crohn's disease (CD) and ulcerative colitis (UC). The intestinal complications of Crohn's disease and ulcerative colitis differ because of the characteristically dissimilar behaviors of the intestinal inflammation in these two diseases.
Scleroderma is an autoimmune disease of the connective tissue. It is characterized by the formation of scar tissue (fibrosis) in the skin and organs of the body, leading to thickness and firmness of involved areas. Scleroderma is also referred to as systemic sclerosis, and the cause is unknown. Treatment of scleroderma is directed toward the individual features that are most troubling to the patient.
Is Diverticulitis Contagious?
Diverticulitis is an inflammation of the diverticula or diverticulum. Diverticulitis causes are either infectious or noninfectious, however, it is not contagoius. Symptoms of diverticulitis include: nausea, vomiting, diarrhea, gas, constipation, changes in bowel habits, bloating, constipation, fever, abdominal tenderness, swollen abdomen, fistula formation, and lower left abdominal pain.
Treatment & Diagnosis
- Penile Discharge
- Vaginal Discharge
- Pelvic Pain
- Helicobacter pylori (H. pylori) Infection
- Crohn's Disease
- Abscessed Tooth
- Giardiasis (Giardia Lamblia Infection)
- Doctor: Checklist to Take To Your Doctor's Appointment
- Inflammatory Bowel Disease
- Pelvic Inflammatory Disease (PID)
- Chronic Fatigue FAQs
- Acne FAQs
- Crohn's Disease FAQs
- Drugs: The Most Common Medication Errors
- Medication Disposal
- Dangers of Mixing Medications
- How To Reduce Your Medication Costs
- Pharmacy Visit, How To Get The Most Out of Your Visit
- Indications for Drugs: Approved vs. Non-approved
- What is Bacterial Vaginosis?
- Drugs: Buying Prescription Drugs Online Safely
- What Are the Side Effects of Taking Antibiotics Long-Term?
- Antibiotics 101
- Generic Drugs, Are They as Good as Brand-Names?
Medications & Supplements
- Metronidazole: Topical (Metrogel, Metrocream, Metrogel Vaginal, and Others)
- Cipro vs. Flagyl (Differences between Side Effects and Uses)
- Drugs: Questions to Ask Your Doctor or Pharmacist about Your Drugs
- Metronidazole (Flagyl) vs. Fluconazole (Diflucan)
- Drug Interactions
- Metronidazole vs. Miconazole
- Metronidazole (Flagyl) vs. Clindamycin (Cleocin)
- Metronidazole vs. Vancomycin
- Metronidazole (Flagyl) vs. azelaic acid (Finacea)
- Flagyl (metronidazole) Side Effects
Prevention & Wellness
- Prescription Meds: Too Common in Pregnancy?
- Once-Daily Ivermectin Is a Safe Rosacea Treatment
- Combination Antibiotic Zerbaxa Approved
- New Antibiotic in the Works for Dangerous C. Diff
- C. diff Infections in Hospitals Are Leveling Off
- C. diff on the Rise Outside the Hospital
- New C. diff Drug OK'd by FDA Panel
Infectious Disease Resources
Health Solutions From Our Sponsors
Health Solutions From Our Sponsors
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
FDA Prescribing Information