INFECTION: QUINOLONES

Question 1

QUINOLONES: INDICATIONS

Answer 1

• Quinolones are generally reserved as second or third-line treatment due to the potential for rapid emergence of resistance and an association with
  Clostridium difficile infection
• With these caveats in mind, they are used in: Urinary tract infection (UTI). Severe gastrointestinal infection, e.g. with Shigella, Campylobacter
• Lower respiratory tract infection (LRTI) (moxifloxacin, levofloxacin)
• Ciprofloxacin is the only oral antibiotic in common use with activity against Pseudomonas aeruginosa
• Moxifloxacin and levofloxacin do not have this property.

Question 2

QUINOLONES: MOA

Answer 2

• inhibiting DNA synthesis. They are particularly active against aerobic Gram-negative bacteria, which explains their utility in treatment of urinary and gastrointestinal infections.

Question 3

QUINOLONES: ADVERSE EFFECTS

Answer 3

• Quinolones are generally well tolerated although they can cause gastrointestinal upset (including nausea and diarrhoea) and immediate and delayed hypersensitivity reactions
• Class-specific adverse reactions include neurological effects (lowering of the seizure threshold and hallucinations), and inflammation and rupture of muscle tendons
• Quinolones (particularly moxifloxacin) prolong the QT interval and therefore increase the risk of arrhythmias
• They promote Clostridium difficile colitis, particularly with the hypervirulent 027 strain

Question 4

QUINOLONES: WARNINGS

Answer 4

• with or at risk of seizures
• who are growing (potential risk of arthropathy); and with other risk factors for QT prolongation (such as cardiac disease or electrolyte disturbance)

Question 5

QUINOLONES: IMPORTANT INTERACTIONS

Answer 5

• Drugs containing divalent cations (e.g. calcium, antacids) reduce absorption and efficacy of quinolones.
• Ciprofloxacin inhibits certain cytochrome P450 enzymes, increasing risk of toxicity with some drugs, notably theophylline
• Co-prescription of NSAIDs increases the risk of seizures, and of prednisolone increases the risk of tendon rupture.
• Quinolones should be prescribed with caution in patients taking other drugs that prolong the QT interval or cause arrhythmias, such as amiodarone, antipsychotics, quinine, macrolide antibiotics and SSRIs.

Question 6

QUINOLONES: EXAMPLES

Answer 6

• ciprofloxacin
• moxifloxacin
• levofloxacin