Therapeutic drug monitoring-guided treatment determination in a ganciclovir-unresponsive lung transplant recipient

Abstract Ganciclovir and valganciclovir are used for cytomegalovirus infection after lung transplantation, but the emergence of resistant viruses complicates treatment. We experienced a lung transplant case where cytomegalovirus reactivation was observed under the valganciclovir prophylaxis. We utilized therapeutic drug monitoring for this case, and immediately suspected that the cytomegalovirus might be resistant to ganciclovir because the area under the curve of ganciclovir was sufficient for prophylaxis. Therefore, we determined to change the antiviral regimen to foscarnet and letermovir, which resulted in immediate cytomegalovirus clearance. This report demonstrated the utility of therapeutic drug monitoring of ganciclovir for suspecting the resistance to ganciclovir.