Flagyl Prescribing Information
WARNING: Metronidazole has been shown to be carcinogenic in mice and rats. (See PRECAUTIONS.) Unnecessary use of this drug should be avoided. Its use should be reserved for the conditions described in the INDICATIONS AND USAGE section below.
Symptomatic Trichomoniasis
Metronidazole is indicated for the treatment of symptomatic trichomoniasis in females and males when the presence of the trichomonad has been confirmed by appropriate laboratory procedures (wet smears and/or cultures).
Asymptomatic Trichomoniasis
Metronidazole is indicated in the treatment of asymptomatic 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 Consorts
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 consort 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 consort should be treated with metronidazole in cases of reinfection.
Amebiasis
Metronidazole is indicated in the treatment of acute intestinal amebiasis (amebic dysentery) and amebic liver abscess. In amebic liver abscess, metronidazole therapy does not obviate the need for aspiration or drainage of pus.
Anaerobic Bacterial Infections
Metronidazole is indicated in the treatment of serious infections caused by susceptible anaerobic bacteria. Indicated surgical procedures should be performed in conjunction with metronidazole therapy. In a mixed aerobic and anaerobic infection, antimicrobials appropriate for the treatment of the aerobic infection should be used in addition to metronidazole.
In the treatment of most serious anaerobic infections, the intravenous form of metronidazole is usually administered initially. This may be followed by oral therapy with metronidazole at the discretion of the physician.
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 niger, and Peptostreptococcus species.
SKIN AND SKIN STRUCTURE INFECTIONS caused by Bacteroides species including the B. fragilis group, Clostridium species, Peptococcus niger, Peptostreptococcus species, and 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 niger, and Peptostreptococcus species.
BACTERIAL SEPTICEMIA caused by Bacteroides species including the B. fragilis group, and 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 metronidazole and other antibacterial drugs, metronidazole 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.
Metronidazole is contraindicated in patients with a prior history of hypersensitivity to metronidazole or other nitroimidazole derivatives.
In patients with trichomoniasis, metronidazole is contraindicated during the first trimester of pregnancy (See WARNINGS).
The most serious adverse reactions reported in patients treated with metronidazole have been 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.
The most common adverse reactions reported have been referable to the gastrointestinal tract, particularly nausea reported by about 12% of patients, sometimes accompanied by headache, anorexia, and occasionally vomiting; diarrhea; epigastric distress; and abdominal cramping. Constipation has also been reported.
The following reactions have also been reported during treatment with metronidazole:
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.
Hematopoietic: Reversible neutropenia (leukopenia); rarely, reversible thrombocytopenia.
Cardiovascular: Flattening of the T-wave may be seen in electrocardiographic tracings.
Central Nervous System: Encephalopathy, aseptic meningitis, convulsive seizures, optic neuropathy, peripheral neuropathy, dizziness, vertigo, incoordination, ataxia, confusion, dysarthria, irritability, depression, weakness, and insomnia.
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.” If patients receiving metronidazole drink alcoholic beverages, they may experience abdominal distress, nausea, vomiting, flushing, or headache. A modification of the taste of alcoholic beverages has also been reported. Rare cases of pancreatitis, which generally abated on withdrawal of the drug, have been reported.
Crohn’s disease patients 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 metronidazole.
Metronidazole is an oral synthetic antiprotozoal and antibacterial agent, 1 (β-hydroxyethyl)-2-methyl-5-nitroimidazole, which has the following structural formula:
Each tablet for oral administration contains 250 mg or 500 mg of metronidazole. Inactive ingredients include microcrystalline cellulose, crospovidone, colloidal silicon dioxide and hydrogenated vegetable oil.
Disposition of metronidazole in the body is similar for both oral and intravenous dosage forms, with an average elimination half-life in healthy humans of eight hours.
The major route of elimination of metronidazole and its metabolites is via the urine (60 to 80% of the dose), with fecal excretion accounting for 6 to 15% of the dose. The metabolites that appear in the urine result primarily from side-chain oxidation [1-(β-hydroxyethyl)-2-hydroxymethyl-5-nitroimidazole and 2-methyl-5-nitroimidazole-1-yl-acetic acid] and glucuronide conjugation, with unchanged metronidazole accounting for approximately 20% of the total. Renal clearance of metronidazole is approximately 10 mL/min/1.73 m2.
Metronidazole is the major component appearing in the plasma, with lesser quantities of the 2-hydroxymethyl metabolite also being present. Less than 20% of the circulating metronidazole is bound to plasma proteins. Both the parent compound and the metabolite possess in vitro bactericidal activity against most strains of anaerobic bacteria and in vitro trichomonacidal activity.
Metronidazole appears in cerebrospinal fluid, saliva, and human milk in concentrations similar to those found in plasma. Bactericidal concentrations of metronidazole have also been detected in pus from hepatic abscesses.
Following oral administration, metronidazole is well absorbed, with peak plasma concentrations occurring between one and two hours after administration.
Plasma concentrations of metronidazole are proportional to the administered dose. Oral administration of 250 mg, 500 mg, or 2,000 mg produced peak plasma concentrations of 6 mcg/mL, 12 mcg/mL, and 40 mcg/mL, respectively. Studies reveal no significant bioavailability differences between males and females; however, because of weight differences, the resulting plasma levels in males are generally lower.
Decreased renal function does not alter the single-dose pharmacokinetics of metronidazole. However, plasma clearance of metronidazole is decreased in patients with decreased liver function.
Microbiology
Trichomonas vaginalis, Entamoeba histolytica
Metronidazole possesses direct trichomonacidal and amebacidal activity against T. vaginalis and E. histolytica. The in vitro minimal inhibitory concentration (MIC) for most strains of these organisms is 1 mcg/mL or less.
Anaerobic Bacteria
Metronidazole is active in vitro against most obligate anaerobes but does not appear to possess any clinically relevant activity against facultative anaerobes or obligate aerobes. Against susceptible organisms, metronidazole is generally bactericidal at concentrations equal to or slightly higher than the minimal inhibitory concentrations. Metronidazole has been shown to have in vitro and clinical activity against the following organisms:
Anaerobic gram-negative bacilli, including:
Bacteroides species including the Bacteroides fragilis group (B. fragilis, B. distasonis, B.ovatus, B. thetaiotaomicron, B. vulgatus)
Fusobacterium species
Anaerobic gram-positive bacilli, including:
Clostridium species and susceptible strains of Eubacterium
Anaerobic gram-positive cocci, including:
Peptococcus niger
Peptostreptococcus species
Susceptibility Tests
Bacteriologic studies should be performed to determine the causative organisms and their susceptibility to metronidazole; however, the rapid, routine susceptibility testing of individual isolates of anaerobic bacteria is not always practical, and therapy may be started while awaiting these results.
Quantitative methods give the most precise estimates of susceptibility to antibacterial drugs. A standardized agar dilution method and a broth microdilution method are recommended.1
Control strains are recommended for standardized susceptibility testing. Each time the test is performed, one or more of the following strains should be included: Clostridium perfringens ATCC 13124, Bacteroides fragilis ATCC 25285, and Bacteroides thetaiotaomicron ATCC 29741. The mode metronidazole MICs for those three strains are reported to be 0.25, 0.25, and 0.5 mcg/mL, respectively.
A clinical laboratory is considered under acceptable control if the results of the control strains are within one doubling dilution of the mode MICs reported for metronidazole.
A bacterial isolate may be considered susceptible if the MIC value for metronidazole is not more than 16 mcg/mL. An organism is considered resistant if the MIC is greater than 16 mcg/mL. A report of “resistant” from the laboratory indicates that the infecting organism is not likely to respond to therapy.
Metronidazole Tablets USP:
250 mg - White, round, convex, unscored tablets debossed on one side with PLIVA 333.
Available in bottles of 100, 250 and 500.
500 mg - White, oblong, convex, unscored tablets debossed on one side with PLIVA 334.
Available in bottles of 100 and 500.
Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature].
PROTECT FROM LIGHT
Dispense in a tight, light-resistant container as defined in the USP, with a child-resistant closure (as required).
KEEP THIS AND ALL MEDICATIONS OUT OF THE REACH OF CHILDREN.
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1. Proposed standard: PSM-11-Proposed Reference Dilution Procedure for Antimicrobic Susceptibility Testing of Anaerobic Bacteria, National Committee for Clinical Laboratory Standards; and Sutter, et al.: Collaborative Evaluation of a Proposed Reference Dilution Method of Susceptibility Testing of Anaerobic Bacteria, Antimicrob. Agents Chemother. 16:495-502 (Oct.) 1979; and Tally, et al.: In Vitro Activity of Thienamycin, Antimicrob. Agents Chemother. 14:436-438 (Sept.) 1978.
2. Ralph, E.D., and Kirby, W.M.M.: Bioassay of Metronidazole With Either Anaerobic or Aerobic Incubation, J. Infect. Dis. 132:587-591 (Nov.) 1975; or Gulaid, et al.: Determination of Metronidazole and Its Major Metabolites in Biological Fluids by High Pressure Liquid Chromatography, Br. J. Clin. Pharmacol. 6:430-432, 1978.
Rx only
Manufactured in Poland By:
PLIVA Krakow Pharmaceutical Company S.A.
Krakow, Poland
Manufactured For:
TEVA PHARMACEUTICALS USA
Sellersville, PA 18960
11001717
Iss. 9/2010
Repacked by:
H.J. Harkins Company, Inc.
513 Sandydale Drive
Nipomo, CA 93444
Central and Peripheral Nervous System Effects
Convulsive seizures, encephalopathy, aseptic meningitis, optic and peripheral neuropathy, the latter characterized mainly by numbness or paresthesia of an extremity, have been reported in patients treated with metronidazole. The appearance of abnormal neurologic signs demands the prompt discontinuation of metronidazole therapy. Metronidazole should be administered with caution to patients with central nervous system diseases.