Uses

This drug is used with probenecid to treat a certain viral eye infection (retinitis due to cytomegalovirus-CMV) in people with AIDS. It lowers your risk of blindness and other vision problems. Cidofovir belongs to a class of drugs known as antivirals. It works by stopping the growth of the virus.

Cidofovir is not a cure for CMV retinitis, and your disease may still worsen during and after treatment.

Other Uses

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used for herpes simplex virus infections that have not responded to other treatment.

How To Use

This medication is given into a vein as directed by your doctor, usually over 1 hour. It is usually given every 1 to 2 weeks or as directed by your doctor. This medication should not be injected into the eyes. Permanent loss of vision may occur.

Dosage is based on your medical condition, body weight, and response to treatment. You will usually receive IV fluids before your dose of cidofovir. Your doctor will also direct you to take probenecid by mouth before and after you receive cidofovir. To prevent kidney problems, drink plenty of fluids unless otherwise directed by your doctor. This is especially important if you are vomiting or having diarrhea.

If you are giving this medication to yourself at home, learn all preparation and usage instructions from your health care professional. Before using, check this product visually for particles or discoloration. If either is present, do not use the liquid. Learn how to store and discard medical supplies safely.

It is very important to use the probenecid with this medication exactly as prescribed by your doctor. Nausea and vomiting due to probenecid may be prevented by taking it after meals. Your doctor may also prescribe another medication to prevent nausea, and may direct you to take antihistamines (such as diphenhydramine) and/or acetaminophen to prevent allergic reactions to probenecid.

This medication works best when it is used regularly. Keep all your medical appointments. You may want to mark a calendar to help you remember.

Do not use more or less of this drug than prescribed or stop using it (or your HIV medicines) even for a short time unless directed to do so by your doctor. Doing so may cause the amount of virus to increase, make the infection more difficult to treat (resistant), or worsen side effects.

Avoid direct contact of this medicine with the skin/eyes/mouth. If contact occurs, wash thoroughly with soap and water. For eyes, rinse with a steady stream of tap water for at least 5 minutes.

Side Effects

See also Warning section.

Nausea may occur. Headache, nausea, and vomiting may occur with probenecid use. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor 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:

• nausea/vomiting that doesn't stop
• dark urine
• swelling
• loss of appetite
• unusual tiredness/sluggishness
• stomach/abdominal pain
• muscle loss
• signs of infection (such as sore throat/cough that doesn't go away, fever)
• vision changes
• new/increased eye redness or irritation
• new/increased eye pain
• mental/mood changes (such as confusion)
• yellowing eyes/skin

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• 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 or at www.fda.gov/medwatch.

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

Precautions

Before using cidofovir, tell your doctor or pharmacist if you are allergic to it; or to other antivirals (such as ganciclovir); or to probenecid; or to other sulfa drugs (such as 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.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• diabetes
• ganciclovir eye implant
• 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.

Older adults 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 effective forms of 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.

Drug Interactions

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• acyclovir
• ACE inhibitors (such as captopril, lisinopril)
• aminosalicylic acid
• barbiturates (such as phenobarbital)
• benzodiazepines (such as triazolam)
• bumetanide
• clofibrate
• methotrexate
• furosemide
• nonsteroidal anti-inflammatory drugs-NSAIDs (such as ibuprofen)
• zidovudine

If you are taking probenecid and any of the medications listed above, ask your doctor if you should temporarily stop the other medication or decrease its dosage because probenecid may affect how well those medications are removed from your body. This is very important for zidovudine.

Tell your doctor if you have had previous use of foscarnet.

Avoid taking other medications that may damage your kidneys (such as amphotericin B, foscarnet, pentamidine, vancomycin, aminoglycosides including tobramycin, nonsteroidal anti-inflammatory drugs-NSAIDs including ibuprofen) within 7 days before and during treatment with this medication. In some cases, serious (possibly fatal) kidney damage may occur. See also Warning section.

Check the labels on all your medicines because they may contain NSAIDs (such as ibuprofen, naproxen). Ask your pharmacist about using those products safely.

Overdose

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Alberta residents can call PADIS (Poison and Drug Information Service) 24 hours a day at 1-800-332-1414. Canada residents can call a provincial poison control center. Symptoms of overdose may include: change in the amount of urine.

Notes

Lab and/or medical tests (such as eye exams) should be done while you are using this medication. Keep all medical and lab appointments. Consult your doctor for more details.

To decrease your risk of spreading HIV disease to others, use an effective barrier method (such as latex or polyurethane condoms/dental dams) during sexual activity. Consult your doctor or pharmacist for more details.

Missed Dose

It is important to get each dose of this medication as scheduled. If you miss a dose of cidofovir, ask your doctor or pharmacist right away for a new dosing schedule. Do not double the dose to catch up. If you miss a dose of the probenecid, tell your doctor or pharmacist right away. You may have to reschedule your cidofovir dose.

If you have questions about missing a dose or you don't have more medication, contact your healthcare provider or pharmacist.

Storage

Consult the product instructions and your pharmacist for storage details. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.