“…Nevertheless, a number of analytical methods have been proposed for the measurement of ganciclovir in biological fluids by high performance liquid chromatography (HPLC), but only a few enable the measurement of aciclovir and/or ganciclovir with the same assay, and none have considered the influence of the metabolite of aciclovir, 9-carboxymethoxymethylguanine (CMMG) [9][10][11] that can potentially interfere with ganciclovir. In fact, CMMG, which has been already analysed together with aciclovir by Svensson et al [12], is at risk of co-eluting with ganciclovir when the latter is used as internal standard, or when previously or subsequently used in the same patient.…”