Macrolides

Question 1

Give 3 examples of macrolides

Answer 1

• Clarithromycin
• Erythromycin
• Azithromycin

Question 2

Are all drugs that end in -mycin macrolides?

Answer 2

No, e.g. neomycin, tobramycin

Question 3

What is the mechanism of action of macrolides?

Answer 3

Inhibit bacterial synthesis by reversibly binding to the 50s subunit on the ribosome, preventing elongation of the bacterial protein chain

Question 4

Are macrolides broad or narrow spectrum?

Answer 4

Broad

Question 5

What are macrolides effective in treating?

Answer 5

Gram +ve and some gram -ve bacteria

Question 6

When might macrolides be used as an alternative to penicillin?

Answer 6

In penicillin allergic patients

Question 7

What are the routes of delivery of macrolides?

Answer 7

PO

IV

Question 8

What are the indications for macrolides?

Answer 8

• Respiratory tract infections
• Mild-moderate soft tissue infections
• As part of H pylori eradication therapy
• Chlamydia trichromatis
• Acne rosaecea
• Lyme disease

Question 9

Give an example of a mild-moderate soft tissue infection that macrolides may be used to treat

Answer 9

Cellulitis

Question 10

What macrolide is used as part of H. Pylori eradication therapy?

Answer 10

Clarithromycin

Question 11

What macrolide is used to treat chlamydia?

Answer 11

Erythromycin

Question 12

What are the cautions for macrolides?

Answer 12

• QT elongation

- Myasthenia gravis

Question 13

Why should macrolides be used with caution in patients with QT elongation?

Answer 13

QT prolongation is a serious side effect of this drug

Question 14

Why should macrolides be used with caution in patients with myasthenia gravis?

Answer 14

Condition can be exacerbated by macrolide use

Question 15

How is azithromycin different from other macrolides in terms of interactions?

Answer 15

It does not inhibit cytochrome P450, and thus is involved in very few drug interactions

so the interactions here may or may not apply to azithro so just check BNF in the exam :)

Question 16

What might macrolides interact with?

Answer 16

• Warfarin
• Statins
• Carbamazepine
• Theophylline and colchine
• Antipsychotics
• Quinolones

Question 17

What might happen if you give warfarin with macrolides?

Answer 17

Increased anticoagulant effect and increased INR

Question 18

What might happen if you give statins with macrolides?

Answer 18

Increased risk of rhabdomyolysis

Question 19

What might happen if you give carbamazepine with macrolides?

Answer 19

Increased serum carbamazepine levels due to CYP450 inhibition, which may result in toxicity

Question 20

What might happen if you give theophylline/colchine with macrolides?

Answer 20

Increased risk of toxicity

Question 21

What might happen if you give antipsychotics with macrolides?

Answer 21

Increased risk of arrhythmias

Question 22

What might happen if you give quinolones with macrolides?

Answer 22

Increased risk of QT prolongation and lowers seizure threshold

Question 23

What monitoring is required with macrolides?

Answer 23

• Consider obtaining baseline ECG, and monitor ECG if cardiac symptoms develop
• Monitor INR closely if on warfarin

Question 24

Why should you consider obtaining a baseline ECG with macrolides?

Answer 24

To exclude cardiac abnormalities that would increase the patient’s risk of developing QT prolongation

Question 25

What are the common or very common side effects of macrolides?

Answer 25

GI disturbances, e.g. abdo pain, diarrhoea, nausea, vomiting

Question 26

How can GI side effects be reduced when giving macrolides?

Answer 26

Giving smaller doses in mild infections

Question 27

What are the less common side effects of macrolides?

Answer 27

• QT interval prolongation
• Hepatotoxicity
• Stevens-Johnson syndrome and TEN
• Pancreatitis
• Cholestatic jaundice
• Hearing loss, generally reversible

Question 28

What patient counselling is required with macrolides?

Answer 28

• Complete antibiotic course

- Signs to watch out for

Question 29

What should patients be warned to look out for with macrolides?

Answer 29

• Severe abdominal pain
• Yellow discolouration of skin or eyes
• Darkened urine
• Pale stools
• Unusual tiredness