clarithromycin: clinical use

Contraindications and cautions

• Hypersensitivity to clarithromycin, another macrolide or a product excipient.
• Known QT prolongation or previous ventricular arrhythmia, including torsades de pointes.
• Hypokalaemia.
• Severe hepatic failure combined with renal impairment.
• Concurrent use with contraindicated interacting medicines, including simvastatin, lovastatin, ergot alkaloids and specified QT-prolonging substrates.

Monitoring

• Clinical response and emergence of superinfection or antimicrobial-associated diarrhoea.
• Renal and hepatic function when impairment, severe illness or prolonged treatment makes this relevant.
• ECG and electrolytes when cardiac risk factors or interacting medicines are present.
• INR with warfarin; medicine concentrations or toxicity signs for narrow-therapeutic-index substrates where appropriate.
• Liver tests and hearing assessment if symptoms or prolonged/high-exposure treatment warrant them.

Clinical pharmacology

Clarithromycin is a macrolide that inhibits bacterial protein synthesis through reversible binding to the 50S ribosomal subunit. It is metabolised mainly by CYP3A4 to an active 14-hydroxy metabolite and is itself a clinically important CYP3A4 and transporter inhibitor.

Formulation and product differences

• Immediate-release tablets are generally taken in divided daily doses and may be taken irrespective of food.
• Xetinin XL is prolonged release, must be taken with food and swallowed whole; it is unsuitable when the required renal dose cannot be achieved.
• Oral suspensions support weight-based paediatric dosing and must be shaken and accurately measured; excipients differ between products.
• The intravenous formulation requires reconstitution and dilution and is administered as an infusion, never as an intravenous bolus or intramuscular injection.