Slideshows Images Quizzes

Flagyl ER

Last reviewed on RxList: 12/15/2016
Flagyl ER Side Effects Center

Last reviewed on RxList 3/5/2016

Flagyl, Flagyl ER, and Flagyl Injection (metronidazole) are all almost identical antimicrobial drugs used to treat bacterial vaginosis (mainly Flagyl ER), trichomonas, amebiasis, and anaerobic bacterial infections. Flagyl ER is available as a generic. Common side effects of Flagyl ER include nausea, stomach pain, abdominal cramps, vomiting, diarrhea, constipation, headache, weight loss (anorexia), dizziness, loss of balance, vaginal itching or discharge, dry mouth, unpleasant metallic taste in the mouth, cough, sneezing, runny or stuffy nose, or swollen or sore tongue.

Flagyl is supplied in 250 and 500 mg strength tablets, Flagyl ER is available in 750 mg strength tablets, and Flagyl Injection in 500 mg strength in a buffered 100 ml vial. Flagyl ER may interact with alcohol, cimetidine, seizure medications, blood thinners, lithium, or disulfiram. Tell your doctor all medications and supplements you use. Dosage is quite variable and dependent upon the severity of disease and other considerations made by the treating physician. Treatment in pregnant women (during first 3 months is not advised) or women who are breastfeeding should only be done if the benefits outweigh the potential problems; Flagyl levels approach serum levels in breast milk. Except for use in amebiasis, studies in pediatric patients are not available; Flagyl ER has no pediatric studies.

Our Flagyl, Flagyl ER and Flagyl Injection Side Effects Drug Centers provide a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Flagyl ER Consumer Information

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

Call your doctor at once if you have any of these serious side effects:

  • numbness or tingling in your hands or feet;
  • white patches or sores inside your mouth or on your lips;
  • pain or burning when you urinate;
  • diarrhea that is watery or bloody;
  • vision problems, pain behind your eyes;
  • trouble concentrating, slurred speech, mood or behavior changes, tremors, muscle twitching, seizure (convulsions);
  • fever, chills, muscle pain, confusion, headache, sore throat, neck stiffness, increased sensitivity to light, drowsiness, nausea and vomiting; or
  • severe skin reaction -- fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain, followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Less serious side effects may include:

  • stomach pain, diarrhea;
  • dizziness, loss of balance;
  • vaginal itching or discharge;
  • dry mouth or unpleasant metallic taste;
  • cough, sneezing, runny or stuffy nose; or
  • swollen or sore tongue.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Flagyl ER (Metronidazole Extended Release Tablets)

Flagyl ER Professional Information

SIDE EFFECTS

In two multicenter clinical trials, a total of 270 patients received 750 mg FLAGYL ER tablets orally once daily for 7 days, and 287 were treated with a comparator agent administered intravaginally once daily for 7 days (See Clinical Studies).5,6

Most adverse events were described as being of mild or moderate severity. Among patients taking FLAGYL ER who reported headaches, 10% considered them severe, and less than 2% of reported episodes of nausea were considered severe. Metallic taste was reported by 9% of patients taking FLAGYL ER.

Adverse events reported at ≥ 2% incidence for either treatment group, irrespective of treatment causality, are summarized in the table below.

Adverse Events ( ≥ 2% Incidence Rate)-Irrespective of Treatment Causality

  FLAGYL ER 7 days
(N=267)
Vaginal Preparation
(N=285)
Headache 48 (18%) 44 (15%)
Vaginitis 39 (15%) 32 (12%)
Nausea 28 (10%) 8 (3%)
Taste Perversion (metallic taste) 23 (9%) 1 (0%)
Infection Bacterial 19 (7%) 17 (6%)
Influenza-like Symptoms 17 (6%) 20 (7%)
Pruritus Genital 14 (5%) 25 (9%)
Abdominal Pain 10 (4%) 13 (5%)
Dizziness 11 (4%) 3 (1%)
Diarrhea 11 (4%) 3 (1%)
Upper Respiratory Tract Infection 11 (4%) 10 (4%)
Rhinitis 12 (4%) 10 (4%)
Sinusitis 7 (3%) 6 (2%)
Urine Abnormal 7 (3%) 4 (1%)
Pharyngitis 8 (3%) 4 (1%)
Dysmenorrhea 9 (3%) 7 (2%)
Moniliasis 9 (3%) 8 (3%)
Mouth Dry 5 (2%) 2 (1%)
Urinary Tract Infection 6 (2%) 16 (6%)

Vulvovaginal candidiasis is a recognized consequence of treatment with many anti-infective agents. In these multicenter clinical trials, there were no statistically significant differences in the incidence rates of yeast vaginitis for groups of patients treated with FLAGYL ER or the vaginal comparator.

The following reactions have been reported during treatment with metronidazole:

Central Nervous System: The most serious adverse reactions reported in patients treated with metronidazole have been convulsive seizures, encephalopathy, aseptic meningitis, optic and peripheral neuropathy, the latter characterized mainly by numbness or paresthesia of an extremity. Since persistent peripheral neuropathy has been reported in some patients receiving prolonged administration of metronidazole, patients should be specifically warned about these reactions and should be told to stop the drug and report immediately to their physicians if any neurologic symptoms occur. In addition, patients have reported headache, syncope, dizziness, vertigo, incoordination, ataxia, confusion, dysarthria, irritability, depression, weakness, and insomnia (See WARNINGS).

Gastrointestinal: The most common adverse reactions reported have been referable to the gastrointestinal tract, particularly nausea, sometimes accompanied by headache, anorexia, and occasionally vomiting, diarrhea, epigastric distress; abdominal cramping; and constipation.

Mouth: A sharp, unpleasant metallic taste is not unusual. Furry tongue, glossitis, and stomatitis have occurred; these may be associated with a sudden overgrowth of Candida which may occur during therapy.

Dermatologic: Erythematous rash and pruritus.

Hematopoietic: Reversible neutropenia (leukopenia); rarely, reversible thrombocytopenia.

Cardiovascular: Flattening of the T-wave may be seen in electrocardiographic tracings.

Hypersensitivity: Urticaria, erythematous rash, Stevens-Johnson Syndrome, toxic epidermal necrolysis, flushing, nasal congestion, dryness of the mouth (or vagina or vulva), and fever.

Renal: Dysuria, cystitis, polyuria, incontinence, and a sense of pelvic pressure. Instances of darkened urine have been reported by approximately one patient in 100,000. Although the pigment which is probably responsible for this phenomenon has not been positively identified, it is almost certainly a metabolite of metronidazole and seems to have no clinical significance.

Other: Proliferation of Candida in the vagina, dyspareunia, decrease of libido, proctitis, and fleeting joint pains sometimes resembling “serum sickness.” Rare cases of pancreatitis, which generally abated on withdrawal of the drug, have been reported.

Patients with Crohn's disease are known to have an increased incidence of gastrointestinal and certain extraintestinal cancers. There have been some reports in the medical literature of breast and colon cancer in Crohn's disease patients who have been treated with metronidazole at high doses for extended periods of time. A cause and effect relationship has not been established. Crohn's disease is not an approved indication for FLAGYL ER 750 mg tablets.

REFERENCES

5. Integrated clinical and statistical report for the treatment of bacterial vaginosis with metronidazole modified release tablet- a dose duration study. G.D. Searle & Co., Protocol No. N13-95-02-015; Report No. N13-96-06-015, 19 Nov 1996.

6. Integrated clinical and statistical report for the treatment of bacterial vaginosis with metronidazole modified release tablet. G.D. Searle & Co., Protocol No. N13-95-02-017; Report No. N13-96-06-017, 11 Nov 1996.

Read the entire FDA prescribing information for Flagyl ER (Metronidazole Extended Release Tablets)

Related Resources for Flagyl ER

Read the Flagyl ER User Reviews »

© Flagyl ER Patient Information is supplied by Cerner Multum, Inc. and Flagyl ER Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

Health Solutions From Our Sponsors