Validated spectrometric determination of penciclovir and entecavir in bulk and in pharmaceutical preparations

Simple, rapid and sensitive spectroscopic methods were developed and validated for the determination of antiviral agents, namely, penciclovir (PCV) and entecavir (ETV). The first method is based on measuring the native fluorescence of each of the cited drugs at its optimum excitation and emission wavelengths. The fluorescence intensity was measured for PCV & ETV at 363 nm and 370 nm upon excitation at 260 nm and 254 nm, respectively. The calibration curves were linear over the concentration range 0.1-0.8, 0.025-0.4 μg ml−1 for PCV and ETV, respectively. The second method is based on measuring the amplitude of ETV in the fourth derivative with Δλ = 8 and scaling factor = 100 at 256.4 nm at which its acidic degradation showed zero reading over the concentration range 5-60 μg ml−1. The proposed methods were applied for the determination of the cited drugs in bulk and pharmaceutical preparations. ICH guidelines were used for method validation.