Macrolides

Question 1

Macrolides - indications

Answer 1

1) Treatment of respiratory, skin and soft tissue infections as an alternative to penicillin when use is contraindicated
2) In severe pneumonia added to a penicillin
3) Eradication of H. Pylori (for example, causing PUD) in combination with PPI + either amoxicillin or metronidazole.

Question 2

Macrolides - examples

Answer 2

clarithromycin

erythromycin

azithromycin

Question 3

Macrolides - MOA

Answer 3

Macrolides inhibit bacterial protein synthesis - how?

1) macrolide binds to the 50S subunit of the bacterial ribosome and block translocation
2) Inhibition of protein synthesis is bacteriostatic (stops bacterial growth)
3) the immune system can then kill and remove the bacteria from the body

Question 4

Macrolides - adverse effects

NOTE: Adverse effects are most common and severe with erythromycin, but can occur with any macrolide

Answer 4

Macrolides are irritant, causing:
IF TAKEN ORALLY 
1) nausea +/- vomiting
2) abdominal pain
3) diarrhoea 

IF IV GIVEN
4) thrombophlebitis

Other side effects include:

1) allergy
2) antibiotic-associated colitis
3) liver abnormalities - including cholestatic jaundice
3) prolongation of the QT interval (predisposing to arrhythmias)
4) ototoxicity at high doses.

Question 5

Macrolides - use with caution in patients with…

Answer 5

1) severe hepatic impairment

2) severe renal impairment - dose reduction

Question 6

Macrolides - avoid in patients with…

Answer 6

• Hx of macrolide hypersensitivity

Question 7

Macrolides - interactions

Answer 7

DRUGS METABOLISED BY CYP ENZYMES (E.G.- WARFARIN + STATINS)
Erythromycin and clarithromycin (but not azithromycin) inhibit cytochrome P450 (CYP) enzymes

DRUGS THAT PROLONG THE QT INTERVAL or cause arrhythmias:

• amiodarone
• antipsychotics
• quinine
• quinolone antibiotics
• SSRIs