azithromycin dihydrate: clinical use

Prescribing considerations

• Confirm a bacterial indication and consider local susceptibility and resistance.
• Review hepatic disease, severe renal impairment, previous antibiotic-associated colitis, myasthenia gravis and QT-prolongation risks before systemic treatment.
• Assess concomitant medicines for QT, P-glycoprotein, anticoagulant and narrow-therapeutic-index interactions.
• For sexually transmitted infections, obtain appropriate microbiological assessment and follow-up; gonococcal infection requires another appropriate antibacterial.
• In neonates with possible chlamydial or gonococcal conjunctivitis, consider associated systemic infection; topical treatment alone may be inappropriate.

Contraindications and cautions

• Hypersensitivity to azithromycin, erythromycin, another macrolide or ketolide, or a formulation excipient.
• Avoid systemic co-administration with ergot derivatives; this combination is contraindicated for the selected infusion.
• Account for formulation-specific excipients, including lactose in tablets and capsules, sulfur dioxide in capsules, sugars and benzyl alcohol in suspension, and sodium in the infusion.

Monitoring

• Investigate liver function promptly and stop treatment if clinical features suggest hepatic dysfunction.
• Assess ECG and correct potassium or magnesium disturbance when clinically indicated.
• Consider additional INR monitoring with warfarin and clinical or concentration monitoring with digoxin, ciclosporin or other relevant narrow-therapeutic-index substrates.
• Investigate severe or persistent diarrhoea during or after treatment for Clostridioides difficile-associated disease.
• In severe infection or treatment failure, obtain microbiology and susceptibility information where feasible.

Clinical pharmacology

Azithromycin is an azalide macrolide that inhibits bacterial protein synthesis at the 50S ribosomal subunit. Oral absorption is formulation-dependent; food reduces capsule exposure. It distributes extensively into tissues and intracellular compartments, producing prolonged tissue persistence. Efficacy is associated mainly with the exposure-to-MIC relationship.

Formulation and product differences

• Film-coated tablets contain lactose and may be taken with or without food.
• Hard capsules contain lactose and sulfur dioxide and require administration away from meals.
• Reconstituted oral suspension contains sucrose, glucose and benzyl alcohol; it may be taken with or without food and must be shaken before measuring.
• Intravenous powder contains sodium, requires reconstitution and further dilution, and is for infusion only.
• Eye drops are oily, preservative-free single-dose containers with negligible systemic exposure; discard after opening.

Solution for infusion

Route: Intravenous

Strengths: 500 mg

Oral suspension

Route: Oral

Strengths: 200 mg/5 mL

Tablet

Route: Oral

Strengths: 250 mg, 500 mg