Precautions
1. Do Not Substitute Valganciclovir for Ganciclovir Capsules on a 1:1 Basis
The absolute bioavailability of valganciclovir, measured as ganciclovir, is approximately 10‑fold higher than that of ganciclovir capsules. Valganciclovir cannot be substituted for ganciclovir capsules on a 1:1 basis. Patients switching from ganciclovir capsules to valganciclovir tablets should be advised that there is a risk of overdosage if they take more than the prescribed dose of valganciclovir (see Dosage and Administration, Overdosage).
2. Monitor Blood Cell Counts During Treatment
Monitoring of complete blood cell counts and platelet counts is recommended during treatment. For patients with severe leukopenia, neutropenia, anemia and/or thrombocytopenia, administration of hematopoietic growth factors and/or temporary discontinuation of therapy should be considered (see Special Dosage Guidelines and Adverse Reactions).
3. Adjust Dosage for Renal Impairment
Dosage adjustment is required for patients with renal impairment based on creatinine clearance (see Special Dosage Guidelines and Pharmacokinetics in Special Populations).
4. Preferred Intravenous Ganciclovir for Hemodialysis Patients
For patients undergoing hemodialysis (CrCl <10 mL/min), intravenous ganciclovir (rather than valganciclovir) is recommended, with dosage calculated using the dose‑reduction formula provided in the approved ganciclovir prescribing information (see Special Dosage Guidelines and Pharmacokinetics in Special Populations).
5. Avoid Activities Requiring Mental Alertness if Adverse Nervous System Reactions Occur
Convulsions, sedation, dizziness, ataxia and/or confusion have been reported following administration of valganciclovir and/or ganciclovir. If these effects occur, they may impair the ability to perform activities requiring mental alertness, including driving or operating machinery.
6. Avoid Concomitant Use with Imipenem-Cilastatin (Tienam) Unless Benefit Outweighs Risk
Seizures have been reported in patients receiving concomitant imipenem‑cilastatin and ganciclovir. Valganciclovir should not be used with imipenem‑cilastatin unless the potential benefit justifies the potential risk.
7. Caution with Concomitant Use of Zidovudine
Both zidovudine and valganciclovir may cause neutropenia and anemia when administered alone. Some patients may not tolerate full doses of the combination.
8. Monitor Didanosine Toxicity When Used Concomitantly
Plasma concentrations of didanosine may be increased during co‑administration with valganciclovir; therefore, patients should be closely monitored for didanosine‑related toxicity.
9. Caution with Concomitant Use of Myelosuppressive or Nephrotoxic Drugs
Concomitant use of valganciclovir with other agents known to cause myelosuppression or be associated with renal dysfunction may result in increased toxicity.
