Metronidazole

Question 1

Metronidazole - indications

SOAAP

Answer 1

1) Antibiotic-associated colitis caused by the Gram (+) anaerobes C. difficile.
2) Oral infections (such as a dental abscess)
3) Aspiration pneumonia caused by Gram(-) anaerobes from the mouth.
4) Surgical and gynaecological infections caused by Gram(-) anaerobes from the colon (e.g.- Bacteroides fragilis)

5) Protozoal infections:
- trichomonal vaginal infection
- amoebic dysentery
- giardiasis.

Question 2

Metronidazole - MOA

Answer 2

1) Metronidazole enters bacterial cells and is reduced to form a free radical
2) This free radical binds to DNA - causing DNA degradation and cell death (bactericidal)

Question 3

Metronidazole - Adverse effects

Answer 3

1) GI upset (such as nausea and vomiting)
2) immediate and delayed hypersensitivity reactions - skin rash, anaphylaxis

3) High doses OR prolonged course can result in neurological adverse effects:
- peripheral and optic neuropathy
- seizures
- encephalopathy.

Question 4

Metronidazole - caution in people with..

Answer 4

severe liver disease - dose reduction

Question 5

Metronidazole - contraindication AND what do you need to explain to the patient in this case?

Answer 5

ALCOHOL

Warn patients not to have alcohol during AND for 48hrs after treatment - explaining that if they do they may feel very unwell with nausea, vomiting, flushing and headache.

Question 6

Metronidazole - interactions

Answer 6

Warfarin (increasing the risk of bleeding)

CYP inducers

• phenytoin
• rifampicin

Lithium (metronidazole increases the risk of toxicity)