Antibiotics: Fluoroquinolones

Question 1

Indications of fluoroquinolones?

Answer 1

UTI (mostly Gram-negative)

Severe gastroenteritis (Shigella, Campylobacter).​

LRTI (gram-positive and gram-negative)​
- moxifloxacin or levofloxacin preferred = new quinolones)

Question 2

Spectrum of activity of fluoroquinolones?

Answer 2

Broad spectrum

Works against Gram-positive and Gram-negative bacteria.

Question 3

MOA of fluoroquinolones?

Answer 3

Inhibits DNA synthesis -BACTERICIDAL (kills bacteria)

Bacteria rapidly develop resistance to quinolones.

Some bacteria reduce permeability and/or increase efflux
→ prevents intracellular drug accumulation ​

Others develop protective mutations in target enzymes.

Question 4

Adverse effects of fluoroquinolones?

Answer 4

GI upset:
- nausea
- diarrhoea

Hypersensitivity reaction

Neurological effects
- lowering seizure threshold
- hallucination

Inflammation and rupture of muscle tendons.

Prolongs QT interval
→ increase risk of arrhythmias

Antibiotic-associated collitis (C.diff)

Question 5

Warnings of fluoroquinolones?

Answer 5

Use with caution in pts at heightened risk of adverse effects e.g:​
- Those who suffer from seizures​
- Children and young adults (potential risk of arthropathy)​
- RFs for QT prolongation (e.g. cardiac disease/electrolyte disturbance)

Question 6

Interactions of fluoroquinolones?

Answer 6

Absorption reduced by drugs containing divalent cations e.g. calcium, antacids.

Ciprofloxacin inhibits certain cytochrome P450 enzymes
→ increases risk of toxicity with drugs like theophylline.​

Fluoroquinolones + NSAIDs = increases risk of seizures.​

Fluoroquinolones + prednisolone = increases risk of tendon rupture.​

Caution in patients taking drugs that prolong the QT interval or cause arrhythmias e.g.:​
- Amiodarone​
- Antipsychotics​
- Quinine​
- Macrolide antibiotics​
- SSRIs

Question 7

Monitoring of fluoroquinolones?

Answer 7

Check improvement in symptoms/signs (e.g. resolution of pyrexia) and blood tests (e.g. falling CRP and WCC).

Question 8

Pt education of fluoroquinolones?

Answer 8

Aims to get rid of infection and improve symptoms.

Check for penicillin allergy.

Seek medical advice if they develop a rash.

If allergy develops during treatment, give pt written and verbal advice NOT to take this abx class in future and make sure that the type of reaction (including its nature) is clearly documented in pt’s medical records.

Question 9

Examples of fluoroquinolones?

Answer 9

ciprofloxacin
moxifloxacin
levofloxacin