Itraconazole (Respiratory)

How it works

Itraconazole inhibits fungal cytochrome P450-dependent synthesis of ergosterol, disrupting the fungal cell membrane and inhibiting growth of Aspergillus and other susceptible fungi.

Prescribing in practice

• It is a potent CYP3A4 inhibitor with extensive, sometimes dangerous drug interactions, so screen co-medication carefully and avoid contraindicated combinations before prescribing.
• Avoid in ventricular dysfunction or heart failure because itraconazole has negative inotropic effects, and monitor for hepatotoxicity.
• Capsule absorption depends on gastric acid and food, so acid-suppressing drugs reduce levels and the formulation and administration conditions matter.

Monitoring

Monitor liver function, signs of cardiac failure, and where indicated plasma drug concentrations to confirm adequate exposure during prolonged therapy.

Counselling the patient

• Tell your team about all other medicines, including over-the-counter ones, because interactions are common.
• Report ankle swelling, breathlessness or symptoms of liver upset such as nausea or yellowing.

Evidence & guidelines

Itraconazole is an established antifungal for aspergillus-related lung disease per BTS and specialist mycology guidance.