Voriconazole interactions: what patients need to know

What is voriconazole?

Voriconazole is an azole antifungal often used in serious fungal infections, including aspergillosis. It can be very effective, but it also has a relatively complex interaction profile.

Why voriconazole interacts with so many medicines

Voriconazole affects several liver enzyme systems, including CYP3A4, CYP2C19, and CYP2C9. It can increase the levels of some medicines, while some other medicines can lower voriconazole levels and reduce its effectiveness.

Because voriconazole metabolism varies between patients, the same combination can affect people differently.

The interaction groups most likely to matter

Steroids

Voriconazole can increase exposure to some steroids, including inhaled steroids, which may increase the risk of steroid side effects.

Medicines that reduce voriconazole levels

Some medicines, including certain anti-seizure medicines and rifampicin-type antibiotics, can reduce voriconazole levels so much that the antifungal may not work properly.

Blood thinners

Some blood thinners may become stronger when taken with voriconazole, increasing bleeding risk.

Heart rhythm medicines

Voriconazole can contribute to QT prolongation, so combinations with other medicines that affect heart rhythm may be particularly important.

Statins

Some statins can become stronger when taken with voriconazole, increasing the risk of muscle side effects.

Immunosuppressants

Medicines such as tacrolimus and ciclosporin can rise significantly with voriconazole and often require specialist monitoring and dose adjustment.

Sedatives and some mental health medicines

Some sedatives and psychiatric medicines can become stronger when combined with voriconazole, increasing the risk of drowsiness, confusion, or other side effects.

Voriconazole-specific issues patients should know

Visual changes

Temporary visual disturbances are well recognised with voriconazole. Patients may notice blurred vision, brighter vision, or changes in colour perception.

Photosensitivity

Voriconazole can increase sensitivity to sunlight. Patients should use sensible sun protection and report new skin changes, especially during long-term treatment.

Variable drug levels

Voriconazole levels can vary between patients, which is one reason some teams use therapeutic drug monitoring in selected situations.

What patients should do in practice

• Tell your clinical team and pharmacist that you are taking voriconazole.
• Check before starting new medicines, including over-the-counter or herbal products.
• Report visual changes, significant sensitivity to sunlight, or a change in symptoms after a medicine change.
• Do not change treatment without advice.

When to seek medical advice

Seek medical advice urgently for severe bleeding, fainting, severe palpitations, marked confusion, or rapid worsening after a medicine change.

References

• BNF: voriconazole monograph and interactions
• UK voriconazole SmPCs