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Metrogyl (Metronidazole) is an oral synthetic antiprotozoal and antibacterial agent.
Tablet: 200-500mg
Injection: 500mg in 100-ml vial
Oral suspension: 200mg (as benzoate)/5 ml

General information:
A 5-nitroimidazole derivative with antimicrobial activity against anaerobic bacteria and some protozoa, including E. histolytica and G. intestinalisMetronidazole is almost completely absorbed following oral administration. Its plasma half-life is about 8 hours and it is expected, largely in the urine, both unchanged and as metabolites.


Treatment of invasive amoebiasis and giardiasis
Patient should subsequently receive a luminal amoebicide to eliminate surviving organisms in the colon.

Mechanism of action:

Metronidazole diffuses in aerobic and anaerobic bacteria equally well, but in the former it remains unchanged while in the later it is reduced. As a result of biomedical reduction in the cell, the concentration of unchanged drug is reduced and is probably creates a gradient which promotes further uptake of the drug in the anaerobic organisms. 

The nitro group of metronidazole is reduced in anaerobic bacteria and protozoa by the pyruvate phosphoroclastic reaction, in which the drug acts as a preferential electron acceptor. It has been assumed that the product of reduction of the nitro group of metronidazole interact with the DNA with ultimate inhibition of nucleic acid synthesis and subsequent death. Moreover metronidazole has been shown to inhibit DNA synthesis and degrade existing DNA in clostridium bifermantans.


·         Symptomatic Trichomoniasis
·         Asymptomatic Trichomoniasis
·         Intestinal Amoebiasis
·         Amoebic liver abscess
·         Anaerobic bacteria infections
·         Intra-abdominal infections
·         Skin and skin structure infections
·         Gynaecologic infections
·         Bacteria septicemia
·         Bone and joint infections
·         Central Nervous System infections
·         Lower respiratory tract infections
·         Endocarditis
Metronidazole should be administered preferably with or immediately after food
Various dosage regimens are used. The following is widely accepted but definitive recommendations should be based on local experience
            Invasive amoebiasis
Adult and children: 30 mg/ kg daily oral in three divided doses after meals for 8-10 days or i.v in three divided injections daily until the patient is able to take oral formulations.
The efficacy of shorter oral regimen is currently being evaluated in controlled trials.

·         Giardiasis
Adults: 2g once daily for 3 days
Children: 15mg/kg daily in divided doses for 5 – 10 days

·         Trichomoniasis in the female:
One day treatment. 2gm of metronidazole given either as a single dose or in two divided doses of 1gm each given in the same day
Seven day course of treatment: 200mg three times daily for seven consecutive days

·         Trichomoniasis in male:
Treatment should be individualized as for the female


·         Known hypersensitivity
·         Early pregnancy
·         Chronic alcohol dependence


Treatment should be discontinued promptly if peripheral neuropathy, ataxia or other signs of central nervous dysfunction occur. Such reactions are extremely rare at the recommended doses. None of the less, patients with active disease of the central nervous system should be particularly carefully monitored.
The blood count should be frequently checked, particularly in patients with a history of blood dyscrasia and when treatment is extended beyond 10 days.
Patients should be warned not to take alcohol during treatment since disulfiram- like reactions can occur.

Use in pregnancy and lactation:

Amoebic dysentery may run a fulminating course during late pregnancy and the pueperium. Treatment with metronidazole may then be life – saving to the mother, but in some cases of severe dysentery surgical resection of the intestine may also be necessary. In less severe infections metronidazole is best avoided in the first trimester since, in animals, it has been shown to have mutagenic and carnigenic potential.
It is advisable during treatment to discontinue breast-feeding, particularly of premature infants

Adverse effects:

Metronidazole is well tolerated but mild symptoms of headache, gastrointestinal irritation and a persistent metallic taste are common. Less frequently, drowsiness, rashes and darkening of urine color
More serious reactions, which are rare, are most likely to occur during extended courses of treatment. 
They include stomatitis and candidiasis, reversible leukopenia and sensory peripheral neuropathy, which is usually mild and rapidly reversible.
Ataxia and epileptiform seizures have been reported among patients receiving dosages considerably higher than those currently recommended.

Drug interactions:

The action of oral anticoagulants is potentiated. Alcohol may induce abdominal pain, vomiting, flushing and headache.
Phenobarbital and corticosteroids lower plasma levels of metronidazole wheres cimetidine raises them.

Tablets and suspensions should be stored in well closed containers, protected from light. Metronidazole injection should be kept in single dose, sealed containers, protected from light.