Itraconazole

How it works

It inhibits fungal cytochrome P450-dependent 14-alpha-demethylase, blocking conversion of lanosterol to ergosterol and disrupting the integrity of the fungal cell membrane.

Prescribing in practice

• Contraindicated in ventricular dysfunction and heart failure because of a negative inotropic effect, and the MHRA warns it can cause or worsen heart failure.
• A potent CYP3A4 inhibitor with extensive, clinically significant interactions; review co-medication and the SPC before starting and stopping.
• Absorption of the capsule is acid-dependent and improved with food, whereas the oral solution is taken without food, so the formulations are not directly interchangeable.

Monitoring

Monitor liver function with prolonged courses and in those with hepatic risk, and assess cardiac status, advising patients to report signs of heart failure or hepatotoxicity.

Counselling the patient

• Take capsules with food and report breathlessness, ankle swelling or unexpected weight gain.
• Tell your team about all other medicines, including those bought without prescription, because of important interactions.
• Report dark urine, pale stools, persistent nausea or yellowing of the skin or eyes.

Evidence & guidelines

Use is guided by the SPC and MHRA safety advice on the risk of heart failure and significant drug interactions.