Metronidazole is the prototype of nitroimidazole that was introduced against trichomoniasis and was later found to be
an active amoebicide.
Indication.
- A first-line drug in the treatment of amoebiasis.
- It has a broad-spectrum activity against ;
√Anaerobic protozoa, including Giardia lamblia.
√ Bacteria such as; Fusobacterium, Clostridium perfringens, Helicobacter pylori, and Campylobacter.
- The drug does not affect aerobic bacteria.
Mechanisms of action.
- After entering the cell by diffusion, the nitro group is reduced by redox proteins to highly reactive nitro radical, which exerts cytotoxicity.
- Covalently binds to DNA, disrupting its helical structure and inhibiting nucleic acid synthesis.
- Metronidazole also inhibits cell-mediated immunity to induce mutagenesis and cause radiosensitization.
Adverse effects
- Flushing, itching, rashes, and urticaria occur in allergic patients.
- Peripheral neuropathy and CNS effects, including seizure and dizziness.
- Anorexia, nausea, glossitis, metallic taste, dryness of the mouth, and abdominal cramps are the most common.
- Leucopenia occurs with repeated courses.
- Thrombophlebitis occurs when the solution is not well diluted before injection.
Contraindications.
- The first trimester of pregnancy and lactation.
- In the case of blood dyscrasias and neurologic diseases.
- Caution when used by chronic alcoholics.
Drug interactions.
- Anticoagulant action of warfarin is enhanced.
- Alcohol-metronidazole drug interaction occurs only in a few individuals, while the majority experience no reaction.
- Enzyme inducers such as; phenobarbitone and rifampin may reduce the drug’s therapeutic effects.
- Cimetidine reduces the metabolism of metronidazole; hence its dose should be decreased.
Dosage.
- FLAGYL, METROGYL, METRON, ARISTOGYL ALDEZOLE 200, 400 mg tablet, 200 mg/5 ml suspension.
- UNIMEZOL 200, 400 mg tablets, 200 mg/5 ml suspension.
- METROGYL GEL, LUPIGYL GEL: 1% gel for vaginal/topical use.
