erythromycin stearate: clinical use

Prescribing considerations

• Confirm a susceptible or reasonably suspected bacterial infection and follow current local antimicrobial policy.
• Review prescribed, over-the-counter and complementary products for CYP3A4, transporter and QT-related interactions.
• Assess cardiac history, bradycardia, coronary disease, heart failure and concurrent QT-prolonging medicines.
• Use caution with hepatic impairment, potentially hepatotoxic medicines and myasthenia gravis.
• In young infants, balance benefit against the increased risk of infantile hypertrophic pyloric stenosis and counsel carers about vomiting or feeding irritability.

Contraindications and cautions

• Hypersensitivity to erythromycin or product excipients
• Congenital or acquired QT prolongation or previous ventricular arrhythmia, including torsades de pointes
• Hypokalaemia or hypomagnesaemia
• Concurrent simvastatin, lomitapide, ergotamine or dihydroergotamine
• Concurrent domperidone, cisapride, pimozide, amisulpride, tolterodine, mizolastine, astemizole or terfenadine

Monitoring

• Consider ECG and electrolyte assessment where cardiac risk factors or interacting medicines are present.
• Monitor liver function when clinically indicated, particularly with hepatic impairment or hepatotoxic co-medication.
• Investigate significant diarrhoea during or after treatment for antibiotic-associated colitis.
• Monitor anticoagulant effect, bleeding, interacting medicine concentrations or toxicity where relevant.
• Assess new muscle pain or weakness promptly when a potentially interacting statin is involved.

Clinical pharmacology

Erythromycin inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit. It is absorbed from the small intestine, distributes widely, undergoes little metabolism and is eliminated principally through the liver. It also inhibits CYP3A4 and relevant uptake or efflux transport pathways.

Formulation and product differences

• The product is a film-coated oral tablet containing erythromycin as the stearate salt.
• Oral suspensions are normally preferred for younger children and people unable to swallow tablets.
• Different erythromycin salts and formulations are not automatically interchangeable without checking the prescribed product.