Full Prescribing Info
Pharmacology: Pharmacodynamics: Metronidazole has activity against protozoa and anaerobic bacteria. It has a wide range of uses including amoebiasis, giardiasis and trichomoniasis, vaginosis, antibiotic-associated colitis, surgical infection prophylaxis, peptic ulcer, inflammatory bowel disease, rosacea and dracunculiasis. Common adverse effects involve the gastrointestinal tract. Neurological effects can occur especially with high doses.
Injection: Metronidazole is active against a variety of anaerobic bacteria particularly Bacteroides fragilis. Its mechanism of action is reflected in a selective toxicity to anaerobic or microaerophilic microorganism and other, anoxic or hypoxic cells. In susceptible cells, the nitro group of metronidazole is reduced by eleCtrotransport proteins with low redox potentials (eg, ferrodoxin in clostridia); these proteins play a much more important role in the metabolism of such cells than do in aerobes. Metronidazole thus, acts as an electron ink and deprives the cell of required reducing equivalents.
Pharmacokinetics: Absorption and Fate: Metronidazole is readily absorbed from the gastrointestinal tract and from the rectal mucosa. It is widely distributed in body tissues. Maximum concentration occurs in the serum after about 1 hr and traces are detected after 24 hrs.
At least ½ the dose is excreted in the urine as metronidazole and its metabolites, including acid oxidation product, a hydroxy derivative and a glucuronide. Metronidazole diffuses across the placenta and is found in breast milk or nursing mothers in concentrations equivalent to those in the serum.
Injection: Disposition of metronidazole in the body is similar for both oral and IV dosage forms, with an average elimination half-life (t½) in healthy humans of 8 hrs.
The major route of elimination of metronidazole and its metabolites is via urine (60-80% of the dose), with fecal excretion accounting for 6-15% 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 glucoronide 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 breast milk in concentrations similar to those found in plasma. Bactericidal concentrations of metronidazole have also been detected in pus from hepatic abscesses.
Decreased renal function dose not alters the single dose pharmacokinetics of metronidazole is decreased in patients with decreased liver function.
Metronidazole has antiprotozoal and antibacterial actions and is effective against Trichomonas vaginalis and other protozoa including Entamoeba histolytica and Giardia lamblia and against anaerobic bacteria.
It is used in the treatment of trichomoniasis of the genitourinary tract in males and females; it does not affect the normal acidophilic flora of the vagina and it has no effect on Candida sp. Resistant strains of T. vaginalis have occasionally been reported. In amoebiasis, it is effective at all sites of infection and is used in the treatment of amoebic dysentery and amoebic liver abscess as well as for the eradication of E. histolytica from patients passing cysts. Metronidazole is also used in the treatment of giardiasis and Vincent's infection, and in the prevention and treatment of anaerobic infections.
Use in Anaerobic Infections: Metronidazole is active against obligate anaerobic bacteria eg, Bacteroides spp and Fusobacterium spp, in the treatment of infections due to such bacteria and in the prevention of postoperative anaerobic infections. It is bactericidal.
Injection: Treatment of infections in which anaerobic bacteria have been identified or are suspected as pathogens, particularly Bacteroides fragilis and other species of bacteriodes and including other species for which metronidazole is bactericidal. For the prevention of post-operative abdominal and pelvic infections due to anaerobic bacteria.
Dosage/Direction for Use
Tablet: Adults: Amoebic Dysentery: Initially 2 g as single dose for 2 days, then 500 mg 3 times a day for 5-10 days.
Hepatic and Other Extraintestinal Amoebiasis: 500-800 mg thrice daily or 2 g as a single dose for 2 days.
Giardiasis: 2 g daily as a single dose for 3 successive days.
Children 7-10 years: ½ of the adult dose.
Suspension: ≥10 years: 1-2 tsp (15-30 mL); 5-10 years: 2 tsp (15-30 mL); 2-5 years: 1 tsp (5 mL). Daily dose is administered every 8 hrs, 1 hr before meal.
Injection: Adults and Children >12 Years: 100 mL by IV 8 hourly. The injection should be infused IV at the rate of 5 mL/min, but may be administered alone or concurrently but separately, with other bacteriological appropriate antibacterial agents in parenteral dosage forms. Oral medication with 400 mg 3 times daily should be substituted as soon as this becomes feasible. Treatment for 7 days should be satisfactorily for most patients but depending upon clinical and bacteriological assessments, the physician might decide to prolong treatment eg, for the eradication of infection from sites which cannot be drained or are liable to endogenous recontamination by anaerobic pathogens from the gut, oropharynx or genital tract.
100 mL by IV infusion immediately before, during or after an operation, followed by the same dose 8 hourly until oral medication can be given to complete a 7-day course. In infants and other patients maintained on IV fluids metronidazole injection may be diluted with appropriate volumes of normal saline, dextro-saline, dextrose 5% or potassium chloride injections. Or prescribed by the physician.
Children <12 Years: As for adults, but the single IV dose is based on 1.5 mL/kg body weight (metronidazole 7.5 mg/kg body mass) and the oral dose of 7 mg/kg body mass. Or as prescribed by the physician.
Injection: Metronidazole should not be used on patients with blood dyscrasias or with active disease of the central nervous system (CNS). Its use should be avoided during pregnancy. If its use is essential during pregnancy the short high dose regimens should not be used.
Metronidazole has been shown to be carcinogenic in mice and possibly carcinogenic in rats. Unnecessary use of Patryl should be avoided.
Special Precautions
Metronidazole should not be used in patients with blood dyscrasias or with active disease of the central nervous system.
Use in pregnancy & lactation: It is suggested that its use should be avoided during pregnancy.
Some authorities consider that women taking metronidazole should not breastfeed their babies.
Use In Pregnancy & Lactation
It is suggested that its use should be avoided during pregnancy.
Some authorities consider that women taking metronidazole should not breastfeed their babies.
Adverse Reactions
Gastrointestinal discomfort, anorexia, nausea, coated tongue, dry mouth, unpleasant taste, headache, pruritus and skin rash. Less frequently vomiting, diarrhea, weakness, vertigo, ataxia, depression and darkening of the urine. Occasionally, there may be temporary moderate leukopenia. Peripheral neuropathy has been reported in patients on prolonged therapy.
Injection: Two (2) serious adverse reactions reported in patients treated with metronidazole have been convulsive seizures 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 Patryl 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 been reported.
The following reactions have also been reported during treatment with metronidazole: Mouth: A sharp, unpleasant metallic taste is not usual. Furry tongue, glossitis and stomatitis have occurred; these may be associated with a sudden overgrowth of Candida which may occur during effective therapy.
Hematopoietic: Reversible neutropenia (leucopenia); rarely, reversible thrombocytopenia.
Cardiovascular: Flattening of the T-wave may be seen in electrocardiographic tracings.
Central Nervous System: Convulsive seizures, peripheral neuropathy, dizziness, vertigo, incoordination, ataxia, confusion, irritability, depression, weakness and insomia.
Hypersensitivity: Urticaria, erythematous rash, 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 1 patientin 100,000. Although the pigment which is probably responsible for this phenomenon has not been postively 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 faints sometimes resembling "serum sickness". A modification of the taste of alcoholic beverages has also been reported. Rare cases of pancreatitis, which abated on withdrawal of Patryl, have been reported. 
Drug Interactions
When given in conjunction with alcohol, metronidazole may provoke a disulfiram-like reaction in some individuals.
Metronidazole enhances the anticoagulant effect of warfarin.
Store at a temperature not exceeding 30°C.
ATC Classification
P01AB01 - metronidazole ; Belongs to the class of nitroimidazole derivatives antiprotozoals. Used in the treatment amoebiasis and other protozoal diseases.
J01XD01 - metronidazole ; Belongs to the class of imidazole derivative antibacterials. Used in the systemic treatment of infections.
Tab 500 mg x 100's. Oral susp 125 mg/5 mL x 60 mL. Inj 5 mg/mL (vial) x 100 mL x 1's.
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