Cidofovir is a treatment for CMV retinitis. CMV is a common infection caused by a herpesvirus called cytomegalovirus. About half of the US population are infected with CMV, but the immune system normally prevents the virus from causing illness. In people with immune system problems such as AIDS, CMV can become active and cause illness. The greatest risk for CMV-related illnesses is for people with T-cell counts of less than 50.

When CMV affects the eyes, it's called CMV retinitis. If CMV retinitis isn't treated, it can cause blindness. CMV can also infect other parts of the body, but retinitis is the most common CMV infection in people with AIDS. Although there is no cure for CMV, treatments like cidofovir can delay progression and help prevent blindness. It is not yet known how well cidofovir can treat CMV in other parts of the body.

Cidofovir is given by intravenous infusion, directly into a vein in the arm. The infusion is given once a week for the first two weeks - this is called the induction treatment. The infusion is then given once every other week to keep the CMV infection under control. You do not need a catheter installed to take cidofovir. A catheter is a device that's permanently placed in your chest if you need to take an intravenous drug regularly.

In clinical trials, cidofovir has been shown to delay progression of CMV retinitis. The average time to any progression of retinitis or stopping of cidofovir treatment was 52 days in a study of people who had not received previous CMV treatment. In a study of people whose CMV retinitis was progressing on other treatments, time to further progression or stopping of cidofovir treatment was 35-49 days, depending on the dose used.

Cidofovir can be harmful to the kidneys. To try and prevent kidney damage, cidofovir is given with a lot of fluids. Probenecid, a drug that helps protect the kidneys, must also be given with cidofovir. Unfortunately, probenecid contains sulfa, a substance that can cause allergic reactions. Side effects caused by reactions to sulfa-containing drugs can include rash and fever.

If someone is taking cidofovir, doctors need to watch for early signs of kidney problems using blood and urine tests. Decreased urination, increased thirst, or light-headedness after standing up can also be early warning signs of kidney problems. If a person already has kidney problems, cidofovir may not be an appropriate treatment for them.

Cidofovir is also being studied in an intravitreal formulation. Intravitreal means the drug is given directly into the eye. The drug may work for longer and cause fewer side effects when given this way. Until studies are completed, the manufacturer recommends that the approved formulation NOT be used in this way due to the risk of hypotony, a shrinkage of the eye that causes blindness.

The other approved anti-CMV drugs are ganciclovir and foscarnet. Ganciclovir is also called Cytovene, and foscarnet is called Foscavir. Both drugs are usually given by daily intravenous infusion. Ganciclovir is now also available as a pill, and the pill can sometimes be used as a maintenance treatment. Ganciclovir is also available in an implant that is placed in the eye called Vitrasert. The Network has Simple Fact Sheets on oral ganciclovir, Vitrasert and CMV. Call to get a free copy.

An alert has been issued about cidofovir causing kidney failure. It is very important to follow the medical guidelines for using cidofovir to avoid this potentially fatal side effect. For copies of the alert and guidelines for medical providers call (800) 445-3235.

Gilead Sciences, the company that makes cidofovir, has set up a patient assistance program for people having difficulty accessing the drug. Call (800) 445-3235 for more information.