SIDE EFFECTS: Nausea may occur. Headache, nausea, and vomiting may occur with probenecid use. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including: change in the amount of urine, frothy/dark urine, bloody/pink urine, swelling, loss of appetite, unusual tiredness/sluggishness, stomach/abdominal pain, muscle loss, signs of infection (e.g., fever, persistent sore throat/cough), vision changes, new/increased eye redness or irritation, new/increased eye pain, mental/mood changes (e.g., confusion), persistent nausea/vomiting, yellowing eyes/skin.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any of the following symptoms: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the Vistide (cidofovir) Side Effects Center for a complete guide to possible side effects »

PRECAUTIONS: Before using cidofovir, tell your doctor or pharmacist if you are allergic to it; or to other antivirals (e.g., ganciclovir); or to probenecid; or to other sulfa drugs (e.g., sulfamethoxazole); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: severe kidney disease.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: diabetes, ganciclovir eye implant, mild/moderate kidney disease.

This drug may cause vision changes. Do not drive, use machinery, or do any activity that requires clear vision until you are sure you can perform such activities safely. Limit alcoholic beverages.

Kidney function declines as you grow older. This medication is removed by the kidneys. Therefore, elderly people may be at a greater risk for kidney damage while using this drug.

During pregnancy, cidofovir should be used only when clearly needed. It may harm an unborn baby. Discuss the risks and benefits with your doctor. The manufacturer recommends avoiding pregnancy. To prevent pregnancy, men with female partners should use effective barrier protections (such as latex or polyurethane condoms) during all sexual activity during treatment and for at least 90 days after stopping the medication. Women should use at least 2 forms of effective birth control (such as birth control pills and condoms) during treatment and for at least 1 month after stopping the medication.

It is not known if this medication passes into breast milk. Because of the possible risks to the infant and because breast milk can transmit HIV, do not breast-feed.