Before taking voriconazole, tell your doctor or pharmacist if you are allergic to it; or to other azole antifungals (such as itraconazole); or if you have any other allergies. This product may contain inactive ingredients (such as lactose), which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: liver disease, heart problems (such as irregular heartbeat).

Voriconazole may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can rarely cause serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that need medical attention right away.

The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may cause QT prolongation. Before using voriconazole, tell your doctor or pharmacist of all the drugs you take and if you have any of the following conditions: certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG), family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death).

Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using voriconazole safely.

This drug may cause vision changes. Do not drive, use machinery, or do anything that needs clear vision until you are sure you can perform such activities safely. Do not drive at night.

Avoid alcoholic beverages since they can increase the risk of serious liver problems.

This medication may make you more sensitive to the sun. It may also increase your risk for skin cancer, especially if you take it for a long time. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned or have skin blisters/redness, or notice new or changed moles/skin lesions.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug, especially QT prolongation (see above).

Children may be at greater risk for liver problems and being more sensitive to the sun while using this drug (see above).

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using voriconazole. Voriconazole may harm an unborn baby. Ask about reliable forms of birth control while using this medication. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

It is unknown if this medication passes into breast milk. Because of the possible risk to the infant, breastfeeding is not recommended while using this medication. Consult your doctor before breastfeeding.