VISTIDE
General description

Vistide is the brand name for the drug cidofovir produced by Gilead Sciences. Cidofovir is an antiviral agent for treating cytomegalovirus (CMV) infection. Gilead produces is as and intravenous inject only.

Mechanism

Cidofovir suprresses CMV replication by selectively inhibiting the viral DNA sythesis. Studies have shown that an activated form of cidofovir can inhibit the DNA polymerase activities and can insert intself into the viral DNA chain, reducing DNA sythesis rates.

Indications

Vistide is indicated for treatment of CMV retinitis in patients with AIDS.

Usage/Dosage

Vistide must be diluted in 100 milliters 0.9% saline prior to administration. it must be adminstered with probenecid and intravenous saline prehydration to minimize potential nephrotoxicity.

Induction treatment is as follows: for patients with seeum creatine of < 1.5 mg/dL, a calculated creatine clearance > 55 mL/min, and a urine protein < 100 mg/dL, it is recommended to administer 5 mg/kg body weight as intravenous infusion at a constant rate over 1 hour. For maintenance treatment it is recommended to adminster 5 mg/kg body weither as an intravenous infusion at a constant rate over 1 hour once every two weeks.

For renal impairment, dosage should be readjusted in the following manner: Vistide dosage must be reduced to 3 mg/kg body weight for an increase in serum creatine of 0.3-0.4 mg/dL above baseline. For increases of serum creatine of >> 3+ proteinuria, treatment should be discontinued. See Contraindications for further recommendations.

Two grams of probenecid must be adminstered orally 3 hours prior to Vistide treatment as well as one gram both 2 and 8 hours after completion of Vistide treatment. Additionally, patients should receive at least 1 liter of 0.9% saline solution intravenously over a 1 to 2 hour period prior to treatment with Vistide. If tolerable, a second saline load should be adminstered with Vistide treatment or immediately following treatment.

Precautions

Since Vistide carries a potential for increased nephroxicity, dosage should not exceeded recommendations. Patients receiving Vistide should know that it is not a cure for CMV retinitis, and the disease can progress during and after treatment, so patients should be under the regular care of a physician during and after treatment. There is little known as to the safety or efficacy of using Vistide to treat CMV infections other than CMV retinitis (such as pneumotitis or gastroenteritis), congenital or neonatal CMV disease, or even CMV disease in non-HIV-infected individuals. Cidofovir is a possible embryotoxic agent, though not many long term effects have been tested in humans. Vistide is not made for intraocular injection. There is little data available regarding resistivity of CMV to Vistidie during and after use.

Contraindications

Vistide is contraindicated for patients with serum creatine > 1.5 mg/dL as well as with patients receiving agents with nephrotoxic potential. These agents should be discontinued at least 7 days prior to beginning treatment with Vistide. Vistide is further contraindicated for patients with a history of hypersensitivity to sidofovir, probenecid, or other sulfa-containing medications.

Potential Adverse Effects

Renal impairment is the major toxic side effect of Vistide. The most serious of these are proteinuria and neutropenia. Other commmon side effects include nausea, vomiting, fever, asthenia, rash, headache, diarrhea, alopecia, infections, chills, anorexia, dyspnea, anemia, creatine elevation, and abdominal pain. In clinical trials, 100% of patients some side side effect, whether minor or major.