Macrolides

Question 1

Give examples of marolides?

Answer 1

Clarithryomycin
Erythromycin
Azithromycin

Question 2

What are common indications?

Answer 2

1.respiratory, skin and tissue infections

2. Severe pneumonia ( with penicillin to broad spectrum of activity to atypical (legionella))
3. Eradication h.pylori

Question 3

What is spectrum of activity?

Answer 3

Broad spectrum
Gram (+) and some (-)

Question 4

Which macrolides are known as synthetic macrolides?

What are their advantages over non- synthetic macrolides?

Answer 4

Clarithryomycin
Azithromycin

They have an increased activity against gram negative bacteria especially H.influenzae

Question 5

What is the mechanism of action?

Answer 5

Inhibit bacterial protein synthesis
Bind to 50s subunit of ribosome
Blocking translocation

This is bacteriostaitc

This aids the immune system in killing and removing bacteria

Question 6

What is mechanism of resistance?

Answer 6

Mutation of ribosome

Question 7

What are important side effects with oral administration ?

Answer 7

Side effects most common in erythromycin

Macrolides are an irritant causing:
Nausea
Vomiting
Abdominal pain
Diarrhoea

Question 8

What are side effects with use at high doses?

Answer 8

Colitis, cholestatic hepatitis, prolongation of QT interval and ototoxicity

Question 9

Who should be prescribed with caution?

Answer 9

Caution in severe hepatic impairment

Dose reduced severe renal impairment

Question 10

What are important interactions?

Answer 10

Ezithromycin and Clarithryomycin both inhibit CYP450 enzymes, increasing their plasma concentrations and increase risk of adverse effects with drugs metabolised by CYP enzymes

QT prolongation drugs should be prescribed with caution

Question 11

What dosage is
Erythromycin prescribed?

Answer 11

Short plasma half life of around 2 hours

250mg-500mg QDS

Question 12

What are dosages of clarithromycin?

Answer 12

Concentrated in tissues and has a longer half life

250-500mg BD

OR

OD as MR

Question 13

What are dosages of azithromycin?

Answer 13

Highly concentrated in tissues and longer half life

250-500mg OD

(Single dose treatment for some infections such as uncomplicated urethritis)

Question 14

What can be done to reduce the risk of arrhythmias with IV use?

Answer 14

Duration of infusion of at least 60 minutes

Question 15

Why should macrolides be diluted in large volumes?

Answer 15

As macrolides given IV are irritant

Question 16

What is an uncommon indication for Azithromycin?

Answer 16

Long term prophylaxis
In COPD severe or prolonged, frequent exacerbations after failure of other treatments

Question 17

What should be monitored with long term treatment of Azithromycin?

Answer 17

monitored for hearing loss and reviewed every 6months, with treatment only continuing if benefits outweigh the risks.