General information: A 5-nitroimidazole derivative with antimicrobial activity against anaerobic bacteria and some protozoa, including E. histolytica and G. intestinalis
Metronidazole 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.
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.
Amoebic liver abscess
Anaerobic bacteria infections
Skin and skin structure infections
Bone and joint infections
Central Nervous System infections
Dosage and administration:
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 ·
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.
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
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 carcinogenic potential. It is advisable during treatment to discontinue breast-feeding, particularly of premature infants
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 epileptic form seizures have been reported among patients receiving dosages considerably higher than those currently recommended.
The action of oral anticoagulants is potentiated. Alcohol may induce abdominal pain, vomiting, flushing and headache. Phenobarbital and corticosteroids lower plasma levels of metronidazole whereas 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. Store below 30°c, in dry place. Keep out of reach of children