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Flagyl (Metronidazole) - Summary



Metronidazole has been shown to be carcinogenic in mice and rats (See PRECAUTIONS). Unnecessary use of the drug should be avoided. Its use should be reserved for the conditions described in the INDICATIONS AND USAGE section below.



FLAGYL (metronidazole) capsules, 375 mg is an oral formulation of the synthetic nitroimidazole antimicrobial agent, 2-methyl-5-nitro-1 H -imidazole-1-ethanol.

Symptomatic Trichomoniasis . FLAGYL 375 capsules are indicated for the treatment of T. vaginalis infection in females and males when the presence of the trichomonad has been confirmed by appropriate laboratory procedures (wet smears and/or cultures).

Asymptomatic Trichomoniasis . FLAGYL 375 capsules are indicated in the treatment of asymptomatic T. vaginalis infection in females when the organism is associated with endocervicitis, cervicitis, or cervical erosion. Since there is evidence that presence of the trichomonad can interfere with accurate assessment of abnormal cytological smears, additional smears should be performed after eradication of the parasite.

Treatment of Asymptomatic Sexual Partners . T. vaginalis infection is a venereal disease. Therefore, asymptomatic sexual partners of treated patients should be treated simultaneously if the organism has been found to be present, in order to prevent reinfection of the partner. The decision as to whether to treat an asymptomatic male partner who has a negative culture or one for whom no culture has been attempted is an individual one. In making this decision, it should be noted that there is evidence that a woman may become reinfected if her sexual partner is not treated. Also, since there can be considerable difficulty in isolating the organism from the asymptomatic male carrier, negative smears and cultures cannot be relied upon in this regard. In any event, the sexual partner should be treated with metronidazole in cases of reinfection.

Amebiasis . FLAGYL 375 capsules are indicated in the treatment of acute intestinal amebiasis (amebic dysentery) and amebic liver abscess.

In amebic liver abscess, FLAGYL 375 capsules therapy does not obviate the need for aspiration or drainage of pus.

Anaerobic Bacterial Infections . FLAGYL 375 capsules are indicated in the treatment of serious infections caused by susceptible anaerobic bacteria. Indicated surgical procedures should be performed in conjunction with FLAGYL therapy. In a mixed aerobic and anaerobic infection, antimicrobials appropriate for the treatment of the aerobic infection should be used in addition to FLAGYL 375 capsules.

INTRA-ABDOMINAL INFECTIONS, including peritonitis, intra-abdominal abscess, and liver abscess, caused by Bacteroides species including the B. fragilis group (B. fragilis, B. distasonis, B. ovatus, B. thetaiotaomicron, B. vulgatus), Clostridium species, Eubacterium species, Peptococcus species, or Peptostreptococcus species.

SKIN AND SKIN STRUCTURE INFECTIONS caused by Bacteroides species including the B. fragilis group, Clostridium species, Peptococcus species, Peptostreptococcus species, or Fusobacterium species.

GYNECOLOGIC INFECTIONS, including endometritis, endomyometritis, tubo-ovarian abscess, and postsurgical vaginal cuff infection, caused by Bacteroides species including the B. fragilis group, Clostridium species, Peptococcus species , Peptostreptococcus species, or Fusobacterium species.

BACTERIAL SEPTICEMIA caused by Bacteroides species including the B. fragilis group or Clostridium species.

BONE AND JOINT INFECTIONS (as adjunctive therapy) caused by Bacteroides species including the B. fragilis group.

CENTRAL NERVOUS SYSTEM (CNS) INFECTIONS, including meningitis and brain abscess, caused by Bacteroides species including the B. fragilis group.

LOWER RESPIRATORY TRACT INFECTIONS, including pneumonia, empyema, and lung abscess, caused by Bacteroides species including the B. fragilis group.

ENDOCARDITIS caused by Bacteroides species including the B. fragilis group.

To reduce the development of drug-resistant bacteria and maintain the effectiveness of FLAGYL 375 capsules and other antibacterial drugs, FLAGYL 375 capsules should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

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Published Studies Related to Flagyl (Metronidazole)

Efficacy and safety of metronidazole for pulmonary multidrug-resistant tuberculosis. [2013]
Pulmonary lesions from active tuberculosis patients are thought to contain persistent, nonreplicating bacilli that arise from hypoxic stress... Newer nitroimidazoles with both aerobic and anaerobic activity, now in clinical trials, may increase the sterilizing potency of future treatment regimens.

Randomised clinical trial: vancomycin or metronidazole in patients with primary sclerosing cholangitis - a pilot study. [2013]
in patients with PSC... CONCLUSIONS: Both vancomycin and metronidazole demonstrated efficacy; however,

Clinical and microbiological benefits of metronidazole alone or with amoxicillin as adjuncts in the treatment of chronic periodontitis: a randomized placebo-controlled clinical trial. [2011.09]
AIM: To evaluate the effects of the adjunctive use of metronidazole (MTZ) or MTZ+amoxicillin (AMX) in the treatment of generalized chronic periodontitis (ChP)... CONCLUSION: The adjunctive use of MTZ+AMX offers short-term clinical and microbiological benefits, over SRP alone, in the treatment of non-smokers subjects with generalized ChP. The added benefits of MTZ were less evident. (c) 2011 John Wiley & Sons A/S.

Helicobacter pylori eradication with a capsule containing bismuth subcitrate potassium, metronidazole, and tetracycline given with omeprazole versus clarithromycin-based triple therapy: a randomised, open-label, non-inferiority, phase 3 trial. [2011.03.12]
BACKGROUND: Helicobacter pylori is associated with benign and malignant diseases of the upper gastrointestinal tract, and increasing antibiotic resistance has made alternative treatments necessary. Our aim was to assess the efficacy and safety of a new, single-capsule treatment versus the gold standard for H pylori eradication... INTERPRETATION: Quadruple therapy should be considered for first-line treatment in view of the rising prevalence of clarithromycin-resistant H pylori, especially since quadruple therapy provides superior eradication with similar safety and tolerability to standard therapy. FUNDING: Axcan Pharma Inc. Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Tinidazole vs metronidazole for the treatment of bacterial vaginosis. [2011.03]
OBJECTIVE: The purpose of this study was to compare the efficacy of 2 different doses of tinidazole with metronidazole for the treatment of bacterial vaginosis and to compare the side effects of the drugs... CONCLUSION: There were no differences in cure rates between metronidazole and either of the tinidazole dosing regimens that were studied. In addition, there were no important differences in the side-effect profiles of metronidazole and tinidazole. Copyright (c) 2011 Mosby, Inc. All rights reserved.

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Clinical Trials Related to Flagyl (Metronidazole)

A Safety, Tolerability and Pharmacokinetic Study of Two Formulations of Metronidazole Versus Immediate Release Metronidazole in Patient With C. Difficile Colitis [Completed]
Clostridium difficile bacteria can be a cause of significant diarrheal disease, particularly in people who have taken potent antibiotics. When C. difficile multiplies within the colon, it produces two toxins that cause inflammation and resultant abdominal pain, fever and diarrhea. Current treatment of mild to moderate disease is with immediate release metronidazole, an antibiotic that kills C. difficile. Dr. Reddy's Laboratories has developed a delayed release form of metronidazole to release just before the colon to increase the concentration of antibiotic in the colon to improve the effectiveness of metronidazole treatment and potentially to allow less whole body exposure to the antibiotic. This study will measure the amount of metronidazole in the blood and stool of patients with C. difficile associated diarrhea (CDAD) to confirm that the new formulations are releasing the antibiotic as designed, immediately before the colon.

Penicillin and Metronidazole in Treatment of Peritonsillar Abscess [Completed]
Treatment of peritonsillar abscess varies. To study whether broad spectrum antibiotics are required in addition to abscess drainage we perform a prospective, double blind, placebo-controlled, randomised study on 200 adult patients with peritonsillar abscess. 100 patients are given penicillin and metronidazole and 100 patients get penicillin and placebo. Recovery and recurrence and analyzed.

Efficacy of Metronidazole Prophylaxis Against Clostridium Difficile-Associated Diarrhea in High Risk Adult Patients [Recruiting]

Efficacy and Safety Study of Metronidazole, Nystatin and Dexamethasone Combination Therapy in Bacterial and Fungal Vaginal Infections [Not yet recruiting]

A Study to Assess the Levels of CAZ-AVI and Metronidazole in the Blood When Given Together and Separately [Completed]
The purpose of the study is to assess whether there is any pharmacokinetic interactions between CAZ-AVI and metronidazole.

more trials >>

Reports of Suspected Flagyl (Metronidazole) Side Effects

Drug Hypersensitivity (39)Nausea (23)Vomiting (20)Diarrhoea (17)Abdominal Pain (15)Urticaria (15)Confusional State (14)Pyrexia (14)NO Adverse Event (14)Clostridium Difficile Colitis (13)more >>


Based on a total of 10 ratings/reviews, Flagyl has an overall score of 3.50. The effectiveness score is 6.40 and the side effect score is 4.20. The scores are on ten point scale: 10 - best, 1 - worst. Below are selected reviews: the highest, the median and the lowest rated.

Flagyl review by 33 year old female patient

Overall rating:  
Effectiveness:   Highly Effective
Side effects:   Mild Side Effects
Treatment Info
Condition / reason:   bacterial vaginosis
Dosage & duration:   One pill a day for 8 days taken once a day for the period of Eight days
Other conditions:   None
Other drugs taken:   None
Reported Results
Benefits:   My infection cleared up almost before the dosage was done. Has not come back.
Side effects:   Mild upset stomach.
Comments:   I took this once a day for eight days for a vaginal bacterial infection. I only had slight side effects of an upset stomach after taking the pill; probably because I had not eaten much on those days. My infection cleared up noticably before the treatement was through. I feel it was very effective.


Flagyl review by 39 year old female patient

Overall rating:  
Effectiveness:   Moderately Effective
Side effects:   Extremely Severe Side Effects
Treatment Info
Condition / reason:   bacterial infectoin
Dosage & duration:   one tablet twice a day taken twice a day for the period of 10 days
Other conditions:   none
Other drugs taken:   None
Reported Results
Benefits:   not worth the cost of the side effects. Becasue I was so miserable, I discontinued the medication early and opted for a more conventional anti-biotic.
Side effects:   nausea, upset stomach, insomnia, and a general feeling sick. I felt like I was going to throw up if I so much as drank water, I got very tired and week but could not sleep due to constant dry heaving.
Comments:   I was told to take it so I did. the more I took the more miserable I got, until I called my doctor and said, I can not take this. I dont know if I am alergic or what but I cant and I wont take any more of it. it still took almost two days for the side effects to go away.


Flagyl review by 43 year old female patient

Overall rating:  
Effectiveness:   Moderately Effective
Side effects:   Extremely Severe Side Effects
Treatment Info
Condition / reason:   gum infection
Dosage & duration:   400 mg tablets taken 2 or 3 daily for the period of 5 days
Other conditions:   no other health problems
Other drugs taken:   nil
Reported Results
Benefits:   the side effects put me in hospital and not able to work for weeks. the gum infection cleared up but this took second place to the concerns during hospitalisation. i did not bounce back to my usual good health after.
Side effects:   irritated heartbeat, palpatations, breathlessness, dizziness, anxiety, flue like symptoms, extreme fatigue, tingling, pain in arm
Comments:   prescribed tablets by Dentist for gum infection. i was told i should take antibiotics but nothing about how it works or side effects. i took the tablets until finished while feeling worse, breathless, dizzy, pain left arm and fatigue but put it down to body fighting gum infection. the day after i finished the full course of tablets i couldn't breath and ready to pass out and went to Doctors and was taken to hospital with heart complications. I have no health problems until now.

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Page last updated: 2014-11-30

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