INFECTION: METRONIDAZOLE Flashcards
1
Q
METRONIDAZOLE: INDICATIONS
A
Tx of infections caused by anaerobic bacteria:
- Antibiotic-associated colitis caused by C.Diff, which is a gram positive anaerobe
- Oral infections or aspiration pneumonia
- Surgical and gynaecological infections
- Tx of protozoal infections (eg trichomonal vaginal infection, ameobic dysentry, giardisis)
2
Q
METRONIDAZOLE: MOA
A
- Metronidazole enters bacterial cells by passive diffusion
- In anaerobic bacteria, reduction of metronidazole generates a nitroso free radical
- This binds to DNA, reducing synthesis and causing widespread damage, DNA degradation and cell death
- As aerobic bacteria are not able to reduce metronidazole in this manner, the spectrum of action of metronidazole is restricted to anaerobic bacteria (and protozoa).
3
Q
METRONIDAZOLE: ADVERSE EFFECTS
A
- GI upset
- Immediate and delayed HSRXns
High dose/pro longed course = neurological adverse effects including peripheral and optic neuropathy, seizures + encephalopathy
4
Q
METRONIDAZOLE: WARNINGS
A
- Metronidazole is metabolised by hepatic cytochrome P450 enzymes, so the dose should be reduced in people with severe liver disease
- Metronidazole inhibits the enzyme acetaldehyde dehydrogenase, which is responsible for clearing the intermediate alcohol metabolite acetaldehyde from the body
- Alcohol should not be drunk while taking metronidazole as the combination can cause a ‘disulfiram-like’ reaction, including flushing, headache, nausea and vomiting
5
Q
METRONIDAZOLE: INTERACTIONS
A
- Metronidazole has some inhibitory effect on cytochrome P450 enzymes, reducing metabolism of warfarin (increasing the risk of bleeding) and phenytoin (increasing the risk of toxicity, including impaired cerebellar function)
- The reverse interaction can occur with cytochrome P450 inducers (e.g. phenytoin, rifampicin) resulting in reduced plasma concentrations and impaired antimicrobial efficacy.
- Metronidazole also increases the risk of toxicity with lithium
