Erythromycin Flashcards
What is erythromycin?
A macrolide antibiotic used for the treatment of infections due to susceptible organisms.
What is erythromycin used for?
Often used to treat infections in place of penicillins
Prophylaxis of bacterial endocarditis and in at risk patients with penicillin allergy and pneumonia.
What are other drugs in this class?
Clarithromycin (not used in NZ)
Roxithromycin
Azithromycin
What is the mechanism of action of erythromycin?
Erythromycin binds to the 50S ribosomal subunit of susceptible bacteria, suppressing protein synthesis.
What are pharmacokinetic/pharmacodynamic characteristics of erythromycin?
Absorption Tmax: 1-4 hours (oral)
Distribution: 75% bound to plasma proteins. Diffuses readily into most body except immune privleged fluids
Metabolised hepatically
Excreted in the bile if oral. If IV, it is excreted in the urine unchanged.
Half life 1.4 hours
What are the precautions of using erythromycin?
Use with caution in patients with predisposition to QT interval prolongation including electrolyte disturbances and concomitant use of drugs that prolong QT interval.
Neonates under 2 weeks at risk of hypertrophic pyloric stenosis
Avoid in acute porphyria
May cause hepatic and renal impairment
Pregnancy class A: not known to be harmful Compatible in breastfeeding
What are the adverse effects of erythromycin?
May cause diarrhoea in infant via breastfeeding
abdominal discomfort, rash.
Rare: pancreatitis, antibiotic associated colitis, arrthmias, hearing loss, Stevens Johnson syndrom
What are some interactions with erythromycin?
High doses of Apo morphine, benperidol, and other QT prolongating drugs => QT prolongation, can lead to fata torsade de pointes
Erythromycin inhibits domperidone metabolism, resulting in 3fold increase in domperidone levels
Erythromycin markedly increases lovastatin, simvastatin and colchicine, exposure including several cases of rhabdomyolysis
Reduces theophylline, clearance leading to toxicity.
Increases concentrations of digoxin, diltiazem, leading to toxicity
What are the alarm bells associated with erythromycin use?
Risk of cardiac arrhythmias: report changes of HR and rhytm to doctor.
Finish the course of medicines
Keep in fridge
