Description
Cidofovir (brand name Vistide®) is a white crystalline powder that is distributed as a clear colorless solution of concentration 75 mg/ml adjusted to pH 7.4. It is designed for intravenous administration as an antiviral agent to AIDS patients suffering from cytomegalovirus (CMV) retinitis.

Disease description
CMV retinitis is a systemic infection commonly seen in patients suffering from AIDS. It is most easily characterized by the cloudiness which can appear in the patients retina. If untreated, the virus will attack retina cells and develop into lesions These lesions can eventually lead to vision impairment or permanent blindness.

Mechanism of action
Acting as an antiviral agent by preventing the replication of CMV, cidofovir targets viral DNA polymerase and prevents transcription. Because the viral polymerase is 8 to 600 times more sensitive than human DNA alpha, beta, and gamma polymerases, the active ingredient, cidofovir diphosphate, is able to specifically target viral replication processes. It must be administered in conjunction with prodenecid in order to block renal tubular secretion of cidofovir.

Clinical Use
First receiving FDA approval for use in the United States in 1996 and then approval for European sale in 1997, Vistide is now sold throughout the US and EU. It should be given at 5mg/kg through an IV. The patient should be given saline prehydration as well as probenecid in order to prevent nephratox. The Vistide cannot be administer though intraocular injection and must be given intravenously. The Vistide must be diluted in 100ml of 0.9% saline before administration.

Standard dose
-Patients with serum creatinine levels of <1.5mg/ml, a calculated creatinine clearance of >55 ml/min, and a urine protein <100mg/dL should receive the treatment once weekly for two weeks. Pediatric dosing has not yet been established.

Dose adjustment
- For an increase of serum creatinine of 0.3-0.4mg/dL. The Vistide treatment should be reduced to 3 mg/kg.
- For an increase of serum creatinine of > 0.5 mg/dL avobe baseline, the treatment should be discontinued

Contraindications
The following patients should not be treated with Vistide:

- Patients who are hypersensitive to cidofovir or probenecid

- Patients who have taken agents with nephrotoxic potential, such as intravenous aminoglycosides, vancomycin, or non-steroidal anti- inflammatory agents, within the past 7 days

- Patients with impaired renal function

Potential Side Effects
- Dose-dependent nephrotoxicity
- Neutropenia
- Metabolic acidosis
- Anterior uveitis
- Proteinuria
- Nausea
- Vomiting
- Asthenia
- Rash
- Headache
- Diarrhea
- Alopecia
- Infection
- Chills
- Anorexia
- Dyspnea
- Anemia
- Abdominal pain

References:
Images and information from:

Gilead Sciences http://www.gilead.com

ePocrates qRx v3.0 http://www.epocrates.com