Macrolides Flashcards
Give 3 examples of macrolides
- Clarithromycin
- Erythromycin
- Azithromycin
Are all drugs that end in -mycin macrolides?
No, e.g. neomycin, tobramycin
What is the mechanism of action of macrolides?
Inhibit bacterial synthesis by reversibly binding to the 50s subunit on the ribosome, preventing elongation of the bacterial protein chain
Are macrolides broad or narrow spectrum?
Broad
What are macrolides effective in treating?
Gram +ve and some gram -ve bacteria
When might macrolides be used as an alternative to penicillin?
In penicillin allergic patients
What are the routes of delivery of macrolides?
PO
IV
What are the indications for macrolides?
- Respiratory tract infections
- Mild-moderate soft tissue infections
- As part of H pylori eradication therapy
- Chlamydia trichromatis
- Acne rosaecea
- Lyme disease
Give an example of a mild-moderate soft tissue infection that macrolides may be used to treat
Cellulitis
What macrolide is used as part of H. Pylori eradication therapy?
Clarithromycin
What macrolide is used to treat chlamydia?
Erythromycin
What are the cautions for macrolides?
- QT elongation
- Myasthenia gravis
Why should macrolides be used with caution in patients with QT elongation?
QT prolongation is a serious side effect of this drug
Why should macrolides be used with caution in patients with myasthenia gravis?
Condition can be exacerbated by macrolide use
How is azithromycin different from other macrolides in terms of interactions?
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 :)
What might macrolides interact with?
- Warfarin
- Statins
- Carbamazepine
- Theophylline and colchine
- Antipsychotics
- Quinolones
What might happen if you give warfarin with macrolides?
Increased anticoagulant effect and increased INR
What might happen if you give statins with macrolides?
Increased risk of rhabdomyolysis
What might happen if you give carbamazepine with macrolides?
Increased serum carbamazepine levels due to CYP450 inhibition, which may result in toxicity
What might happen if you give theophylline/colchine with macrolides?
Increased risk of toxicity
What might happen if you give antipsychotics with macrolides?
Increased risk of arrhythmias
What might happen if you give quinolones with macrolides?
Increased risk of QT prolongation and lowers seizure threshold
What monitoring is required with macrolides?
- Consider obtaining baseline ECG, and monitor ECG if cardiac symptoms develop
- Monitor INR closely if on warfarin
Why should you consider obtaining a baseline ECG with macrolides?
To exclude cardiac abnormalities that would increase the patient’s risk of developing QT prolongation
What are the common or very common side effects of macrolides?
GI disturbances, e.g. abdo pain, diarrhoea, nausea, vomiting
How can GI side effects be reduced when giving macrolides?
Giving smaller doses in mild infections
What are the less common side effects of macrolides?
- QT interval prolongation
- Hepatotoxicity
- Stevens-Johnson syndrome and TEN
- Pancreatitis
- Cholestatic jaundice
- Hearing loss, generally reversible
What patient counselling is required with macrolides?
- Complete antibiotic course
- Signs to watch out for
What should patients be warned to look out for with macrolides?
- Severe abdominal pain
- Yellow discolouration of skin or eyes
- Darkened urine
- Pale stools
- Unusual tiredness
