Drug Interaction Report

GENERALLY AVOID: The use of ganciclovir or its prodrug, valganciclovir, with other drugs associated with myelosuppression and/or nephrotoxicity may increase the risk and severity of these adverse reactions due to additive effects on the kidney and bone marrow. Valganciclovir is rapidly and extensively converted to ganciclovir, which has had the following adverse reactions observed with its treatment when used alone: severe leucopenia, neutropenia, anemia, thrombocytopenia, pancytopenia, bone marrow depression, aplastic anemia, increased serum creatinine levels, and acute renal failure. Additionally, ganciclovir is primarily renally excreted; therefore, patients with impaired renal function will have increased concentrations of ganciclovir and may be at an even greater risk of experiencing adverse reactions from treatment. Theoretically when two or more medications with similar side effect profiles are given concurrently, the likelihood of experiencing these adverse reactions may be increased.

MANAGEMENT: Ganciclovir or its prodrug, valganciclovir, should generally not be combined with other drugs associated with myelosuppression and/or nephrotoxicity unless the benefits are anticipated to outweigh the potential risks. Extreme caution is advised if they are used in patients who have recently received or are receiving treatment with myelotoxic and/or nephrotoxic drugs, and vice versa. If coadministration is required, reduced dosages of one or more of the drugs may be required, and the patient should be monitored for the development of hematologic and/or renal adverse effects both during and after discontinuation of therapy.

ADJUST DOSING INTERVAL: Food increases the bioavailability of ganciclovir from the prodrug, valganciclovir. In 16 HIV-positive subjects, the administration of valganciclovir 875 mg once daily with a high-fat meal containing approximately 600 calories resulted in a 30% increase in the steady-state area under the plasma concentration-time curve (AUC) and a 14% increase in the peak plasma concentration (Cmax) of ganciclovir, with no delay in the time to reach peak plasma concentration (Tmax). The mechanism is unknown.

MANAGEMENT: The manufacturer recommends that valganciclovir be taken with meals.