Metronidazole

Pharmaceuticals

Pharmaceuticals -> Antibiotics (Nitroimidazole)

Pharmaceuticals -> Listed in ZINC15

Pharmaceuticals -> Used in Switzerland

Pharmaceutical

Pharmaceuticals -> Antibiotics

log Kow = -0.02

-0.1

Cream-colored crystals

WHITE TO PALE YELLOW CRYSTALS OR CRYSTALLINE POWDER

less than 1 mg/mL at 68 °F (NTP, 1992)

g/100 ml at 20 °C: 1.0 in water, 0.5 in ethanol, less than 0.05 in ether, chloroform; sol in dilute acids; sparingly sol in dimethylformamide

In water, 11,000 mg/L at 25 °C

5.92e+00 g/L

>25.7 [ug/mL] (The mean of the results at pH 7.4)

Breast Feeding; Lactation; Milk, Human; Anti-Infective Agents; Antibacterial Agents; Antiprotozoal Agents; Nitroimidazoles

FDA approved drugs -> Active ingredient

FDA approved drugs -> Active ingredient

Access group antibiotics

Active Ingredients (Metronidazole) -> FDA Greenbook

Pharmaceuticals -> Animal Drugs -> Approved in Taiwan

Pharmaceuticals -> UK Veterinary Medicines Directorate List

316 to 320 °F (NTP, 1992)

158-160 °C

160 °C

Metronidazole is a white to pale-yellow crystalline powder with a slight odor. Bitter and saline taste. pH (saturated aqueous solution) about 6.5. (NTP, 1992)

Solid

Stable in air but darkens on exposure to light.

Metronidazole conventional tablets should be stored in well-closed, light-resistant containers at less than 25 °C. Metronidazole capsules should be stored in tight containers at 15-25 °C. Metronidazole extended-release tablets should be stored in well-closed containers at approximately 25 °C; temporary exposure to temperatures of 15-30 °C is acceptable.

Metronidazole hydrochloride powder for injection should be protected from light and stored at less than 30 °C. Metronidazole injection should be protected from light and freezing and stored at 15-30 °C. The manufacturer (Baxter) of commercially available metronidazole injection ... states that this injection has an expiration date of 24 months following the date of manufacture.

This chemical does not meet GHS hazard criteria for 1.1% (2 of 177) of reports.

Danger

H302 (15.3%): Harmful if swallowed [Warning Acute toxicity, oral]

P203, P260, P261, P264, P270, P271, P273, P280, P301+P317, P302+P352, P304+P340, P317, P318, P319, P321, P330, P362+P364, P405, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 177 reports by companies from 31 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Hazard Traits - Carcinogenicity

Status: Active Update: 12-03-2020 https://echa.europa.eu/registration-dossier/-/registered-dossier/22643

Metronidazole: Does not have an individual approval but may be used under an appropriate group standard

SYMPTOMS: Symptoms of exposure to this chemical may include nerve or sheath structural changes, eye changes, tremors, fever, jaundice and other liver changes. It may cause convulsive seizures, numbness, nausea, vomiting, abdominal discomfort, diarrhea, sharp, unpleasant metallic taste, erythematous rash, pruritus, dizziness, syncope, ataxia, thrombophlebitis after intravenous infusion, darkened urine, anorexia, epigastric distress, constipation, glossitis, stomatitis, reversible thrombocytopenia and vertigo. Flattening of the T-wave may be seen in electrocardiographic tracings. It may also cause incoordination, irritability, depression, weakness, insomnia, nasal congestion dysuria, cystitus, polyuria, incontinence, a sense of pelvic pressure, dyspareunia, decrease of libido, proctitis and fleeting joint pains sometimes resembling serum sickness. It may cause skin rash and drowsiness. Other symptoms of exposure include malaise, transient rashes, gastrointestinal disturbances and peripheral neuropathy. It may cause coated tongue, dry mouth, urethral discomfort, temporary leukopenia, increase in chromosome aberrations, candidal vaginitis, lethargy and sore furred tongue. In conjunction with alcohol it may provoke a disulfuram-like reaction. Pregnant women expose to this compound have given birth to premature, stillborn infants. One infant has died of white asphyxia. It may cause epigastric distress, abdominal cramping, numbness or paresthesia of an extremity, urticaria, flushing, dryness of vagina or vulva, abdominal distress, headache (if ingested with alcohol), confusional and psychotic states, blood dyscrasias, temporary neutropenia which reverses after therapy, and low concentrations of lipids in plasma.

The Approved Drug Products with Therapeutic Equivalence Evaluations List identifies currently marketed prescription drug products, incl metronidazole, approved on the basis of safety and effectiveness by FDA under sections 505 of the Federal Food, Drug, and Cosmetic Act.

National Toxicology Program. Eleventh Report on Carcinogens (2005). The Report on Carcinogens is an informational scientific and public health document that identifies and discusses substances (including agents, mixtures, or exposure circumstances) that may pose a carcinogenic hazard to human health. Metronidazole (443-48-1) is listed as reasonably anticipated to be a human carcinogen.[Available from, as of July 31, 2009: http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s112metr.pdf]

As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their future use. Under this pesticide reregistration program, EPA examines health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether they are eligible for reregistration. In addition, all pesticides must meet the new safety standard of the Food Quality Protection Act of 1996. Pesticides for which EPA had not issued Registration Standards prior to the effective date of FIFRA, as amended in 1988, were divided into three lists based upon their potential for human exposure and other factors, with List B containing pesticides of greater concern and List D pesticides of less concern. Metronidazole is found on List C. Case No: 3096; Pesticide type: antimicrobial; Case Status: No products containing the pesticide are actively registered ... The case /is characterized/ as "cancelled." Under FIFRA, pesticide producers may voluntarily cancel their registered products. EPA also may cancel pesticide registrations if registrants fail to pay required fees or make/meet certain reregistration commitments, or if EPA reaches findings of unreasonable adverse effects.; Active ingredient (AI): metronidazole; Data Call-in (DCI) Date(s): 09/23/93; AI Status: The active ingredient is no longer contained in any registered pesticide products ... "cancelled."

PRECAUTIONS FOR "CARCINOGENS": Procurement ... of unduly large amt ... should be avoided. To avoid spilling, carcinogens should be transported in securely sealed glass bottles or ampoules, which should themselves be placed inside strong screw-cap or snap-top container that will not open when dropped & will resist attack from the carcinogen. Both bottle & the outside container should be appropriately labelled. ... National post offices, railway companies, road haulage companies & airlines have regulations governing transport of hazardous materials. These authorities should be consulted before ... material is shipped. /Chemical Carcinogens/

PRECAUTIONS FOR "CARCINOGENS": When no regulations exist, the following procedure must be adopted. The carcinogen should be enclosed in a securely sealed, watertight container (primary container), which should be enclosed in a second, unbreakable, leakproof container that will withstand chem attack from the carcinogen (secondary container). The space between primary & secondary container should be filled with absorbent material, which would withstand chem attack from the carcinogen & is sufficient to absorb the entire contents of the primary container in the event of breakage or leakage. Each secondary container should then be enclosed in a strong outer box. The space between the secondary container & the outer box should be filled with an appropriate quantity of shock-absorbent material. Sender should use fastest & most secure form of transport & notify recipient of its departure. If parcel is not received when expected, carrier should be informed so that immediate effort can be made to find it. Traffic schedules should be consulted to avoid ... arrival on weekend or holiday ... /Chemical Carcinogens/

EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

PRECAUTIONS FOR "CARCINOGENS": Storage site should be as close as practical to lab in which carcinogens are to be used, so that only small quantities required for ... expt need to be carried. Carcinogens should be kept in only one section of cupboard, an explosion-proof refrigerator or freezer (depending on chemicophysical properties ...) that bears appropriate label. An inventory ... should be kept, showing quantity of carcinogen & date it was acquired ... Facilities for dispensing ... should be contiguous to storage area. /Chemical Carcinogens/

PRECAUTIONS FOR "CARCINOGENS": A high-efficiency particulate arrestor (HEPA) or charcoal filters can be used to minimize amt of carcinogen in exhausted air ventilated safety cabinets, lab hoods, glove boxes or animal rooms ... Filter housing that is designed so that used filters can be transferred into plastic bag without contaminating maintenance staff is avail commercially. Filters should be placed in plastic bags immediately after removal ... The plastic bag should be sealed immediately ... The sealed bag should be labelled properly ... Waste liquids ... should be placed or collected in proper containers for disposal. The lid should be secured & the bottles properly labelled. Once filled, bottles should be placed in plastic bag, so that outer surface ... is not contaminated ... The plastic bag should also be sealed & labelled. ... Broken glassware ... should be decontaminated by solvent extraction, by chemical destruction, or in specially designed incinerators. /Chemical Carcinogens/

SMALL SPILLS AND LEAKAGE: If you spill this chemical, FIRST REMOVE ALL SOURCES OF IGNITION, then dampen the solid spill material with toluene, then transfer the dampened material to a suitable container. Use absorbent paper dampened with toluene to pick up any remaining material. Your contaminated clothing and absorbent paper should be sealed in a vapor-tight plastic bag for eventual disposal. Solvent-wash all contaminated surfaces with toluene followed by washing with a soap and water solution. Do not reenter the contaminated area until the Safety Officer (or other responsible person) has verified that the area has been properly cleaned.

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

PRECAUTIONS FOR "CARCINOGENS": There is no universal method of disposal that has been proved satisfactory for all carcinogenic compounds & specific methods of chem destruction ... published have not been tested on all kinds of carcinogen-containing waste. ... summary of avail methods & recommendations ... /given/ must be treated as guide only. /Chemical Carcinogens/

PRECAUTIONS FOR "CARCINOGENS": ... Incineration may be only feasible method for disposal of contaminated laboratory waste from biological expt. However, not all incinerators are suitable for this purpose. The most efficient type ... is probably the gas-fired type, in which a first-stage combustion with a less than stoichiometric air:fuel ratio is followed by a second stage with excess air. Some ... are designed to accept ... aqueous & organic-solvent solutions, otherwise it is necessary ... to absorb soln onto suitable combustible material, such as sawdust. Alternatively, chem destruction may be used, esp when small quantities ... are to be destroyed in laboratory. /Chemical Carcinogens/

PRECAUTIONS FOR "CARCINOGENS": HEPA (high-efficiency particulate arrestor) filters ... can be disposed of by incineration. For spent charcoal filters, the adsorbed material can be stripped off at high temp & carcinogenic wastes generated by this treatment conducted to & burned in an incinerator. ... LIQUID WASTE: ... Disposal should be carried out by incineration at temp that ... ensure complete combustion. SOLID WASTE: Carcasses of lab animals, cage litter & misc solid wastes ... should be disposed of by incineration at temp high enough to ensure destruction of chem carcinogens or their metabolites. /Chemical Carcinogens/

For more Disposal Methods (Complete) data for METRONIDAZOLE (6 total), please visit the HSDB record page.

PRECAUTIONS FOR "CARCINOGENS": Smoking, drinking, eating, storage of food or of food & beverage containers or utensils, & the application of cosmetics should be prohibited in any laboratory. All personnel should remove gloves, if worn, after completion of procedures in which carcinogens have been used. They should ... wash ... hands, preferably using dispensers of liq detergent, & rinse ... thoroughly. Consideration should be given to appropriate methods for cleaning the skin, depending on nature of the contaminant. No standard procedure can be recommended, but the use of organic solvents should be avoided. Safety pipettes should be used for all pipetting. /Chemical Carcinogens/

PRECAUTIONS FOR "CARCINOGENS": In animal laboratory, personnel should remove their outdoor clothes & wear protective suits (preferably disposable, one-piece & close-fitting at ankles & wrists), gloves, hair covering & overshoes. ... Clothing should be changed daily but ... discarded immediately if obvious contamination occurs ... /also,/ workers should shower immediately. In chemical laboratory, gloves & gowns should always be worn ... however, gloves should not be assumed to provide full protection. Carefully fitted masks or respirators may be necessary when working with particulates or gases, & disposable plastic aprons might provide addnl protection. If gowns are of distinctive color, this is a reminder that they should not be worn outside of lab. /Chemical Carcinogens/

PRECAUTIONS FOR "CARCINOGENS": ... Operations connected with synth & purification ... should be carried out under well-ventilated hood. Analytical procedures ... should be carried out with care & vapors evolved during ... procedures should be removed. ... Expert advice should be obtained before existing fume cupboards are used ... & when new fume cupboards are installed. It is desirable that there be means for decreasing the rate of air extraction, so that carcinogenic powders can be handled without ... powder being blown around the hood. Glove boxes should be kept under negative air pressure. Air changes should be adequate, so that concn of vapors of volatile carcinogens will not occur. /Chemical Carcinogens/

PRECAUTIONS FOR "CARCINOGENS": Vertical laminar-flow biological safety cabinets may be used for containment of in vitro procedures ... provided that the exhaust air flow is sufficient to provide an inward air flow at the face opening of the cabinet, & contaminated air plenums that are under positive pressure are leak-tight. Horizontal laminar-flow hoods or safety cabinets, where filtered air is blown across the working area towards the operator, should never be used ... Each cabinet or fume cupboard to be used ... should be tested before work is begun (eg, with fume bomb) & label fixed to it, giving date of test & avg air-flow measured. This test should be repeated periodically & after any structural changes. /Chemical Carcinogens/

For more Preventive Measures (Complete) data for METRONIDAZOLE (9 total), please visit the HSDB record page.

RECOMMENDED RESPIRATOR: Where the neat test chemical is weighed and diluted, wear a NIOSH-approved half face respirator equipped with a combination filter cartridge, i.e. organic vapor/acid gas/HEPA (specific for organic vapors, HCl, acid gas, SO2 and a high efficiency particulate filter). (NTP, 1992)

PRECAUTIONS FOR "CARCINOGENS": ... Dispensers of liq detergent /should be available./ ... Safety pipettes should be used for all pipetting. ... In animal laboratory, personnel should ... wear protective suits (preferably disposable, one-piece & close-fitting at ankles & wrists), gloves, hair covering & overshoes. ... In chemical laboratory, gloves & gowns should always be worn ... however, gloves should not be assumed to provide full protection. Carefully fitted masks or respirators may be necessary when working with particulates or gases, & disposable plastic aprons might provide addnl protection. ... Gowns ... /should be/ of distinctive color, this is a reminder that they are not to be worn outside the laboratory. /Chemical Carcinogens/

It is recommended that metronidazole not be used concurrently with, or for at least 1 day following, ingestion of alcohol; accumulation of acetaldehyde by interference with the oxidation of alcohol may occur, resulting in disulfiram-like effects such as abdominal cramps, nausea, vomiting, headache, or flushing; in addition, modifications in the taste of alcoholic beverages have been reported during concurrent use.

Effects may be potentiated when /coumarin- or indandione-derivative anticoagulants/ are used concurrently with metronidazole, because of inhibition of enzymatic metabolism of anticoagulants; periodic prothrombin time determinations may be required during therapy to determine if dosage adjustments of anticoagulants are necessary.

Hepatic metabolism of metronidazole may be decreased when metronidazole and cimetidine are used concurrently, possibly resulting in delayed elimination and increased serum metronidazole concentrations; monitoring of serum concentrations as a guide to dosage is recommended since dosage adjustments of metronidazole may be necessary during and after cimetidine therapy.

It is recommended that metronidazole not be used concurrently with, or for 2 weeks following, disulfiram in alcoholic patients; such use may result in confusion and psychotic reactions because of combined toxicity.

For more Interactions (Complete) data for METRONIDAZOLE (12 total), please visit the HSDB record page.

Despite the wide use of metronidazole, only rare cases of hepatotoxicity have been reported, and metronidazole is not listed among causes of drug induced liver injury and acute liver failure in large case series. High doses of metronidazole given parenterally or in an overdose can cause elevations in serum aminotransferase levels, but these are usually self-limited and minimally symptomatic (Case 1). Acute, clinically apparent liver injury from metronidazole is rare. Ornidazole, another synthetic nitroimidazole that was available in Europe, was implicated in several cases of drug induced liver injury, with a latency of a few days or weeks and a hepatocellular pattern of injury. Metronidazole has been associated with a similar acute hepatitis-like syndrome with a short incubation period, but much more rarely. Fever, rash and eosinophilia are uncommon as are autoimmune features. A fatal recurrence of acute liver injury after reexposure to metronidazole has been published (Case 2). Strikingly, multiple instances of metronidazole hepatoxicity have been reported in the rare genetic disease, Cockayne syndrome in which there is an absence or deficiency in an important DNA repair enzyme responsible for nucleotide excision repair. The cases were marked by a short latency (1 to 7 days) to onset of jaundice, a hepatocellular pattern of enzyme elevations and severe course with a high mortality rate. Whether patients with Cockayne syndrome have a similar high risk for severe hepatitis with other nitroimidazoles (such as tinidazole) is not known.

LD50 Anas platyrhynchos (Mallard duck, 19 weeks old) oral >5000 mg/kg

LC50 Anas platyrhynchos (Mallard duck, 17 days old) diet >5000 ppm/8 days

LC50 Colinus virginianus (Bobwhite quail, 12 days old) diet >5000 ppm/8 days

LC50 Americamysis bahia (Opossum shrimp, age 2 days) 182 ppm/96 hr (95% confidence limit: 140-230 ppm); static /98% AI formulated product/

For more Ecotoxicity Values (Complete) data for METRONIDAZOLE (10 total), please visit the HSDB record page.

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 23(SRC), determined from a log Kow of -0.02(2) and a regression-derived equation(3), indicates that metronidazole is expected to have very high mobility in soil(SRC). Volatilization of metronidazole from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.7X10-11 atm-cu m/mole(SRC), using a fragment constant estimation method(4). Metronidazole is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 3X10-7 mm Hg(SRC), determined from a fragment constant method(5). Biodegradation half-lives in sandy soil-manure slurry of 9.7 to 14.7 days and in clay soil-manure slurry of 13.1 to 26.9 days(5), suggesting biodegradation may be an important environmental fate process in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 23(SRC), determined from a log Kow of -0.02(2) and a regression-derived equation(3), indicates that metronidazole is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 1.7X10- 11 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). According to a classification scheme(5), an estimated BCF of 3(SRC), from its log Kow(2) and a regression-derived equation(6), suggests the potential for bioconcentration in aquatic organisms is low(SRC). No biodegradation was observed using closed bottle tests(7), suggesting that biodegradation is a slow environmental fate process in water(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), metronidazole, which has an estimated vapor pressure of 3.1X10-7 mm Hg at 25 °C(SRC), determined from a fragment constant method(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase metronidazole is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 41 hrs(SRC), calculated from its rate constant of 9.3X10-12 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Particulate-phase metronidazole may be removed from the air by wet or dry deposition(SRC). Metronidazole does not contain chromophores that absorb at wavelengths >290 nm and therefore is not expected to be susceptible to direct photolysis by sunlight(SRC).

The primary adverse effects of metronidazole include confusion, peripheral neuropathy, metallic taste, nausea, vomiting, and diarrhea. Adverse events seen in greater than 10% of the population include headache (18%), vaginitis (15%), and nausea (10% to 12%). Adverse events affecting less than 10% of the population are metallic taste (9%), dizziness (4%), genital pruritus (5%), abdominal pain (4%), diarrhea (4%), xerostomia (2%), dysmenorrhea (3%), urine abnormality (3%), urinary tract infection (2%), bacterial infection (7%), candidiasis (3%), flu-like symptoms (6%), upper respiratory tract infection (4%), pharyngitis (3%), and sinusitis (3%). Rarely, there are reports of transient leukopenia and neutropenia as well.

There have been reports of disulfiram-like reactions in patients drinking alcohol while administered systemic or vaginal metronidazole. A typical disulfiram reaction causes flushing, tachycardia, palpitations, nausea, and vomiting. Alcohol should be avoided during treatment and from up to forty-eight hours to fourteen days after treatment completion, depending on the source; the manufacturer's product information recommends avoiding alcohol ingestion during metronidazole therapy and for at least 48 hours afterward. Ethanol-containing medications such as elixirs and tipranavir, capsules, intravenous (IV) anidulafungin, IV trimethoprim-sulfamethoxazole, and many cough/cold syrups can also lead to a disulfiram-like reaction when ingested with metronidazole.

Metronidazole is a prodrug. Unionized metronidazole is selective for anaerobic bacteria due to their ability to intracellularly reduce metronidazole to its active form. This reduced metronidazole then covalently binds to DNA, disrupt its helical structure, inhibiting bacterial nucleic acid synthesis and resulting in bacterial cell death.

Adverse effects include reversible peripheral neuropathy with prolonged therapy, CNS toxicity, disulfiram effect with alcohol, dark red-brown urine, metallic taste, nausea, epigastric distress, dizziness, vertigo and paresthesias associated with high doses, and neutropenia (reversible and mild).

Metronidazole may be released to treatment systems as a result of excretion and disposal of unused or expired medications(1). An estimated 20 to 40% of outdated and unused medications are disposed down household drains in Germany(2). A theoretical mean effluent concentration of metronidazole was calculated to be 6.2 ug/L from 1992 to 1994 in one hospital(3).

PRECAUTIONS FOR "CARCINOGENS": Whenever medical surveillance is indicated, in particular when exposure to a carcinogen has occurred, ad hoc decisions should be taken concerning ... /cytogenetic and/or other/ tests that might become useful or mandatory. /Chemical Carcinogens/

The Koc of metronidazole is estimated as 23(SRC), using a log Kow of -0.02(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that metronidazole is expected to have very high mobility in soil.

The Approved Drug Products with Therapeutic Equivalence Evaluations List identifies currently marketed prescription drug products, incl metronidazole, approved on the basis of safety and effectiveness by FDA under sections 505 of the Federal Food, Drug, and Cosmetic Act.

As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their future use. Under this pesticide reregistration program, EPA examines health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether they are eligible for reregistration. In addition, all pesticides must meet the new safety standard of the Food Quality Protection Act of 1996. Pesticides for which EPA had not issued Registration Standards prior to the effective date of FIFRA, as amended in 1988, were divided into three lists based upon their potential for human exposure and other factors, with List B containing pesticides of greater concern and List D pesticides of less concern. Metronidazole is found on List C. Case No: 3096; Pesticide type: antimicrobial; Case Status: No products containing the pesticide are actively registered ... The case /is characterized/ as "cancelled." Under FIFRA, pesticide producers may voluntarily cancel their registered products. EPA also may cancel pesticide registrations if registrants fail to pay required fees or make/meet certain reregistration commitments, or if EPA reaches findings of unreasonable adverse effects.; Active ingredient (AI): metronidazole; Data Call-in (DCI) Date(s): 09/23/93; AI Status: The active ingredient is no longer contained in any registered pesticide products ... "cancelled."

J01XD01

P - Antiparasitic products, insecticides and repellents

J - Antiinfectives for systemic use

D - Dermatologicals

A - Alimentary tract and metabolism

G - Genito urinary system and sex hormones

Metronidazole treats amebiasis, trichomoniasis, and giardiasis, exerting both antibacterial and antiprotozoal activities. Metronidazole is an effective treatment for some anaerobic bacterial infections. Metronidazole has shown antibacterial activity against the majority of obligate anaerobes, however, during in vitro studies, it does not demonstrate significant action against facultative anaerobes or obligate aerobes. The nitro group reduction of metronidazole by anaerobic organisms is likely responsible for the drug's antimicrobial cytotoxic effects, causing DNA strand damage to microbes. A note on convulsions and neuropathy and carcinogenesis It is important to be aware of the risk of peripheral neuropathy and convulsions associated with metronidazole, especially at higher doses. If convulsions or numbness of an extremity occur, discontinue the drug immediately. Metronidazole has been found to be carcinogenic in mice and rats. The relevance to this effect in humans is unknown. It is advisable to only administer metronidazole when clinically necessary and only for its approved indications.

The exact mechanism of action of metronidazole has not been fully established, however, it is possible that an intermediate in the reduction of metronidazole which is only made by anaerobic bacteria and protozoa, binds deoxyribonucleic acid and electron-transport proteins of organisms, blocking nucleic acid synthesis. After administration, metronidazole enters cells by passive diffusion. Following this, ferredoxin or flavodoxin reduce its nitro group to nitro radicals. The redox potential of the electron transport portions of anaerobic or microaerophilic microorganisms renders metronidazole selective to these organisms, which cause nitro group reduction, leading to the production of toxic metabolites. These include N-(2-hydroxyethyl) oxamic acid and acetamide, which may damage DNA of replicating organisms.

Microbicidal; active against most obligate anaerobic bacteria and protozoa by undergoing intracellular chemical reduction via mechanisms unique to anaerobic metabolism. Reduced metronidazole, which is cytotoxic but short-lived, interacts with DNA to cause loss of helical structure, strand breakage, and resultant inhibition of nucleic acid synthesis and cell death.

Metronidazole is bactericidal, amebicidal, and trichomonacidal in action. The exact mechanism of action of the drug has not been fully elucidated. Metronidazole is un-ionized at physiologic pH and is readily taken up by anaerobic organisms or cells. In susceptible organisms or cells, metronidazole is reduced by low-redox-potential electron transport proteins (e.g., nitroreductases such as ferredoxin) to unidentified polar product(s) which lack the nitro group. The reduction product(s) appears to be responsible for the cytotoxic and antimicrobial effects of the drug which include disruption of DNA and inhibition of nucleic acid synthesis. Metronidazole is equally effective against dividing and nondividing cells.

In in vivo studies in rats given metronidazole in dosages of 2-4 mg/100 g of body weight, the drug reportedly inhibited the development of formalin-induced edema in the rat paw. In vitro in neutrophils, metronidazole has a dose-dependent inhibitory effect on generation of hydrogen peroxide and hydroxyl radicals, oxidants that may cause tissue injury at the site of inflammation. This antioxidant effect appears to be caused by a direct effect on neutrophil function and may contribute to the drug's anti-inflammatory effect in vivo.

Results of in vitro studies using leukocytes obtained from patients with Crohn's disease indicate that exposing the cells to metronidazole concentrations of 10 or 50 mcg/mL improved both spontaneous and induced leukocyte migration in cells that previously exhibited reduced migration; the drug had no effect on leukocytes obtained from healthy adults or patients with Crohn's disease when the cells exhibited normal migration prior to exposure to the drug. This effect on leukocyte migration also was observed in vivo in adults with Crohn's disease who received a single 400-mg dose of metronidazole. It has been suggested that metronidazole may increase leukocyte migration by a direct effect on the leukocytes, possibly by causing the release of surface-bound immune complexes from the cell surface.

The elimination half-life of metronidazole is 7.3 ± 1.0 after a single 500mg IV dose in healthy subjects. Another resource indicates that the elimination half-life for metronidazole ranges from 6 to 10 hours.

The plasma half-life of metronidazole is reported to be 6-8 hours in adults with normal renal and hepatic function. In one study using radiolabeled metronidazole hydrochloride, the half-life of unchanged metronidazole averaged 7.7 hours and the half-life of total radioactivity averaged 11.9 hours. The plasma half-life of metronidazole is not affected by changes in renal function; however, the half-life may be prolonged in patients with impaired hepatic function. In one study in adults with alcoholic liver disease and impaired hepatic function, half-life of metronidazole averaged 18.3 hours (range: 10.3-29.5 hours).

Half-life: Neonates 25-75 hours; Others: 6-8 hours, increases with hepatic impairment.

The elimination half-life in dogs is 4.5hr, and in horses 1.5-3.3hr

Metronidazole undergoes hepatic metabolism via hydroxylation, oxidation, and glucuronidation. The metabolism of metronidazole yields 5 metabolites. The hydroxy metabolite, 1-(2-hydroxy-ethyl)-2-hydroxy methyl-5-nitroimidazole, is considered the major active metabolite. Unchanged metronidazole is found in the plasma along with small amounts of its 2- hydroxymethyl metabolite. Several metabolites of metronidazole are found in the urine. They are primarily a product of side-chain oxidation in addition to glucuronide conjugation. Only 20% of the dose found in the urine is accounted for by unchanged metronidazole. The two main oxidative metabolites of metronidazole are hydroxy and acetic acid metabolites.

Approximately 30-60% of an oral or IV dose of metronidazole is metabolized in the liver by hydroxylation, side-chain oxidation, and glucuronide conjugation. The major metabolite, 2-hydroxy metronidazole, has some antibacterial and antiprotozoal activity.

... Four other nitro-group-containing metabolites have been identified, each derived from side-chain oxidation of ethyl and/or methyl group. They include 1-acetic acid-2-methyl-5-nitroimidazole and 1-(2-hydroxyethyl)-2-carboxylic acid-5-nitroimidazole salt.

The liver is the main site of metabolism, and this accounts for over 50% of the systemic clearance of metronidazole. The 2 principal metabolites result from oxidation of side chains, a hydroxy derivative and an acid. The hydroxy metabolite has a longer half-life (about 12 hr) and nearly 50% of the antitrichomonal activity of metronidazole. Formation of glucuronides also is observed. Small quantities of reduced metabolites, including ring-cleavage products, are formed by the gut flora. The urine of some patients may be reddish-brown owing to the presence of unidentified pigments derived from the drug.

Hepatic metabolism by hydroxylation, oxidation, and glucuronidation. Half Life: 6-8 hours

140QMO216E

METRONIDAZOLE

Established Pharmacologic Class [EPC] - Nitroimidazole Antimicrobial

Chemical Structure [CS] - Nitroimidazoles

Metronidazole is a Nitroimidazole Antimicrobial.

METRONIDAZOLE

Substances that prevent infectious agents or organisms from spreading or kill infectious agents in order to prevent the spread of infection.

Substances that are destructive to protozoans.

Substances that inhibit the growth or reproduction of BACTERIA.

After the intravenous infusion of a 1.5g dose, peak concentration was reached within 1 hour and was peak level of 30-40 mg/L. When a multiple-dose regimen of 500mg three times a day administered intravenously, steady-state concentrations were achieved within about 3 days and peak concentration was measured at 26 mg/L. When administered orally in the tablet form, metronidazole is absorbed entirely absorbed, showing a bioavailability of greater than 90%. One resource indicates that Cmax after a single oral dose of 500mg metronidazole ranges from 8 to 13 mg/L, with a Tmax of 25 minutes to 4 hours. The AUC following a single 500mg oral dose of metronidazole was 122 ± 10.3 mg/L • h. A note on the absorption of topical preparations Insignificant percutaneous absorption of metronidazole occurs after the application of 1% metronidazole cream topically. Healthy volunteers applied one 100 mg dose of 14C-labelled metronidazole 2% cream to unbroken skin. After 12 hours, metronidazole was not detected in the plasma. Approximately 0.1% to 1% of the administered metronidazole was measured in the urine and feces.

Metronidazole and metabolites are 60 to 80% eliminated in the urine, and 6-15% excreted in the feces.

Metronidazole is widely distributed throughout the body and various body fluids. They include the bile, saliva, breastmilk, cerebrospinal fluid, and the placenta. Steady-state volume distribution of metronidazole in adults ranges from 0.51 to 1.1 L/kg. It attains 60 to 100% of plasma concentrations in various tissues, such as the central nervous system, however, is not measured in high concentrations in the placental tissue.

Dose adjustments may be required in patients with hepatic impairment, as clearance is impaired in these patients. The clearance of metronidazole in the kidneys is estimated at 10 mL/min/1.73 m2. The total clearance from serum is about 2.1 to 6.4 L/h/kg.

Well absorbed orally; bioavailability at least 80%.

Distributed to saliva, bile, seminal fluid, breast milk, bone, liver and liver abscesses, lungs, and vaginal secretions; crosses the placenta and blood-brain barrier, also.

For Metronidazole (USEPA/OPP Pesticide Code: 120401) there are 0 labels match. /SRP: Not registered for current use in the U.S., but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./

The active ingredient is no longer contained in any registered pesticide products ... "cancelled."

Mesh Heading: Anti-infective agents, antiprotozoal agents, radiation-sensitizing agents

Topical treatment of inflammatory lesions of rosacea

For more Uses (Complete) data for METRONIDAZOLE (8 total), please visit the HSDB record page.

Use (kg) in Switzerland (2009): >1000

Jacob et al., US patent 2,944,061 (1960 to Rhone-Poulenc)

Metronidizole is prepared by heating 2-methyl-5-nitroimidizole with excess 2-chloroethanol to obtain the crude product which is purified by extraction with chloroform and recrystallization from ethyl acetate.

Metronidazole, USP (flagyl), is avail as 250-mg tablets. Uncoated vaginal inserts, each containing 500 mg, are also available.

Capsule 375 mg; Gel, topical 0.75% [7.5 mg/mL] (30 g); Gel, vaginal 0.75% (5 g applicator delivering 37.5 mg in 70 g tube); Injection, ready to use 5 mg/mL (100 mL); Powder for injection, as hydrochloride 500 mg; Tablet 250mg, 500 mg

Capsules 375 mg, Tablets 250 mg, 500 mg Flagyl 375, Pfizer; Tablets, extended-release, film-coated 750 mg Flagyl ER, Pfizer; Tablets, film-coated 250 mg, 500 mg Flagyl, Pfizer; Parenteral Injection, for IV infusion only 5 mg/mL Flagyl I.V. RTU (Viaflex [Baxter]), SCS Pharmaceuticals.

Animal Drugs -> FDA Approved Animal Drug Products (Green Book) -> Active Ingredients

Veterinary Drug -> ANTIPROTOZOAL_AGENT -> JECFA Functional Classes

Veterinary Drug -> ANTIPROTOZOAL_AGENT -> JECFA Functional Classes

Pharmaceuticals -> Animal Drugs -> Approved in Taiwan

Although metronidazole is closely related to natural antitrichomonal agent, Azomycin, it is not known to occur in nature.

NMR spectroscopy & polarography were used to detect in vitro interactions between metronidazole & biologically important metals. Only cupric ion showed detectable interaction.

Reasonably anticipated to be a human carcingen