Simultaneous Determination of Aciclovir and Ganciclovir in Plasma by HPLC and Pharmacokinetic Interactions

In this study, we developed a simultaneous determination of the antiviral drugs, aciclovir and ganciclovir, in patient and rat plasma. We also confirmed any potent pharmacokinetic interactions between these two drugs. Precipitation and extraction of aciclovir, ganciclovir, and an internal standard (5-fluoro-2′-deoxyuridine) was achieved by adding 12.5% trichloroacetic acid solution. Separation of the three compounds was performed by a reversed-phase liquid chromatography, and the peaks of compounds were detected spectrophotometerically at 280 nm. The working curves by a least-squares linear regression over the range 0.1–10 μg ML−1 passed through the origin with a correlation coefficient of 0.999 or better, and the results of within-day and between-day precisions were adequate for clinical use. The therapeutic windows of aciclovir and ganciclovir (from the lower to the upper quartile), estimated by measuring clinical plasma samples, were from 0.40 to 0.63 μg mL−1 and from 0.29 to 0.51 μg mL−1, respectively. The trough plasma concentrations of ganciclovir from patients with bone marrow transplants increased significantly when aciclovir was co-administered, and the area under the concentration-time curve of ganciclovir and aciclovir after intravenous coadministration of these drugs in rats showed approximately 2.4- and 1.5-fold increase, respectively, suggesting the existence of some drug interaction between aciclovir and ganciclovir. The HPLC assay method developed here could be used for the rapid pharmacokinetic study in rats and the clinical monitoring of the concentrations of aciclovir and ganciclovir in human plasma with a minimum sample volume of 100 μL.