Therapeutic Drug Monitoring of Ganciclovir in Cytomegalovirus-Infected Patients With Solid Organ Transplants and Its Correlation to Efficacy and Toxicity

Cytomegalovirus causes morbidity and mortality, especially in immunocompromised patients, and is treated with (val)ganciclovir. Therapeutic drug monitoring of ganciclovir is often performed; however, clinically established target trough levels corresponding to efficacy are lacking. In 2021, our clinic increased the target trough level for ganciclovir from 1 to 2 mg/L to 2–4 mg/L. This study aims to compare both target trough levels in efficacy, toxicity, and occurrence of resistance. METHODS: A retrospective cohort study was performed in adult solid organ recipients treated for cytomegalovirus infection with (val)ganciclovir. Clinical efficacy was defined as the absence of treatment failure, defined as > 1 log(10) increase in viral load within 2 weeks of treatment initiation, therapy switch to foscarnet, and/or request for resistance analysis. RESULTS: A total of 46 patients were involved in the study, with 200 ganciclovir trough levels obtained. The composite endpoint was recorded in 23 (69.7%) and 10 (76.9%) patients in the 1–2 mg/L and the 2–4 mg/L group, respectively (P = 0.18). No association was found between ganciclovir trough levels and the composite endpoint (P = 1.0). However, a correlation was found between ganciclovir trough levels and the occurrence of lymphopenia (P = 0.02). CONCLUSIONS: Our study could not establish a difference in clinical efficacy or toxicity between target trough levels of 1–2 mg/L or 2–4 mg/L because of the lack of clinical differences between the compared groups. However, a correlation was found between ganciclovir trough levels and lymphopenia, which warrants further investigation.