Cytomegalovirus Breakthrough in Pediatric Cardiac Transplant Recipients Receiving Weight-Based Dosing Valganciclovir Prophylaxis.

OBJECTIVE: Valganciclovir is an antiviral used to prevent CMV infection. The optimal dosing strategy remains uncertain as manufacturer and weight-based dosing strategies exist. This study aims to define the risk of CMV breakthrough using a weight-based dosing approach for valganciclovir. METHODS: This is a retrospective, single-center study. All patients who received a heart transplant at <18 years of age from January 2011 to August 2022 and were initiated on valganciclovir prophylaxis were eligible for inclusion. Patients were excluded if they required cardiac re-transplantation. The primary outcome was the incidence of CMV breakthrough on a weight-based dose. Secondary outcomes included median difference in daily dose between 2 dosing strategies, incidence of CMV disease, and adverse events. RESULTS: Thirty-four patients met eligibility for inclusion. The median age at transplant was 3.45 years (range, 0.07-16.87). Thirty-three patients were high- or intermediate-risk for CMV infection. There was no difference in initial valganciclovir dose in patients with CMV breakthrough compared with those without (median: 23.9 mg/kg vs 23.6 mg/kg, p = 0.238). The median weight-based total daily dose (23.9 mg/kg) was found to be significantly lower than the median manufacturer-recommended dose (34.3 mg/kg) (p < 0.001). This study found no significant difference in the daily dose of valganciclovir in patients with and without CMV breakthrough. Use of the manufacturer's equation for the initial dosing regimen produced significantly higher daily doses. CONCLUSIONS: This study's findings suggest implementation of a standard dosing procedure may be useful in optimizing prophylaxis with valganciclovir.