Itraconazole interactions: what patients need to know

What is itraconazole?

Itraconazole is an azole antifungal used in aspergillosis and other fungal infections. It has a relatively high interaction burden, so medicine checks are especially important before starting it and whenever another medicine is added, stopped, or changed.

Why itraconazole interacts with so many medicines

Itraconazole can increase the levels of some other medicines by affecting liver enzymes, especially CYP3A4. This means that some medicines may become stronger than intended, which can increase the risk of side effects or toxicity.

The interaction groups most likely to matter

Steroids and inhalers

This is one of the most important groups for many aspergillosis patients, especially those with asthma or allergic bronchopulmonary aspergillosis. Itraconazole can increase exposure to some steroids, including inhaled steroids, which may increase the risk of steroid side effects.

Possible symptoms to report: unusual weight gain, easy bruising, increased facial rounding, mood changes, worsening blood sugar control, weakness, or marked fatigue.

Statins

Some statins can become much stronger when taken with itraconazole. This can increase the risk of muscle toxicity.

Possible symptoms to report: new muscle pain, muscle weakness, or dark urine.

Blood thinners

Itraconazole can increase the effect of some blood thinners, which may raise bleeding risk.

Possible symptoms to report: unusual bruising, bleeding that is hard to stop, black stools, vomiting blood, or coughing up much more blood than usual.

Heart and rhythm medicines

Some combinations can increase the risk of serious heart rhythm problems. Itraconazole is also used cautiously in people with a history of ventricular dysfunction or heart failure unless the infection is serious.

Possible symptoms to report: fainting, palpitations, marked dizziness, increasing ankle swelling, or worsening breathlessness.

Sleeping tablets, sedatives, and some mental health medicines

Some sedatives and psychotropic medicines can become stronger when combined with itraconazole, increasing the risk of drowsiness, confusion, falls, or breathing problems.

Immunosuppressants

Medicines such as tacrolimus and ciclosporin can rise significantly when taken with itraconazole and usually need specialist monitoring.

Medicines that can make itraconazole less effective

Some medicines lower itraconazole levels, which means the antifungal may not work as well. This can happen with some anti-seizure medicines, rifampicin-type antibiotics, and some antiviral medicines.

Acid-reducing medicines and itraconazole capsules

Reduced stomach acid can lower the absorption of itraconazole capsules. This means reflux medicines, antacids, and some acid-suppressing treatments can affect how well the capsules work. The liquid formulation behaves differently and should not be treated as interchangeable with capsules.

What patients should do in practice

• Keep a current medicines list and bring it to appointments.
• Tell clinicians and pharmacists if you are taking itraconazole.
• Ask specifically about inhalers, steroid tablets, statins, blood thinners, and reflux treatment.
• Do not change doses or stop medicines without advice.
• If your itraconazole formulation changes, ask whether it should be taken with food or on an empty stomach.

When to seek medical advice

Seek urgent medical advice for severe bleeding, black stools, vomiting blood, severe muscle pain, fainting, marked palpitations, or rapidly worsening breathlessness.

References

• BNF: itraconazole monograph and interactions
• UK itraconazole SmPCs