Stability Indicating RP-HPLC Method for Simultaneous Estimation of Nirmatrelvir and Ritonavir in Bulk and Tablets

A newer, simple, accurate, precise and selective reversed phase high performance liquid chromatographic method for the simultaneous estimation of Nirmatrelvir and Ritonavir in bulk and formulation has been developed and validated. The method was performed using a 250x4.6mm,5µ Agilent Eclipse XDB coloumn with Acetonitrile: Octane sulphonic acid Buffer pH 2.5(30:70 v/v) used as a mobile phase with the flow of 1.0mL/min. PDA detection was done at 287nm. Nirmatrelvir and Ritonavir were eluted with retention time of 2.312 and 4.238 min, respectively. The ICH guidelines were followed during the validation process. The procedure is fast, precise, accurate and repeatable. Calibration curves were linear in a concentration range of Nirmatrelvir was 37-225 and Ritonavir was 25-150µg/mL. Limits of detection were 0.45 and 0.3µg/mL and limits of quantification were 1.5 and 1µg/mL for Nirmatrelvir and Ritonavir respectively. The best way to simultaneously determine these two drugs in bulk and formulation is supported by the method's low coefficients of variation and high recovery. Stress factors such as acidic, basic, oxidative, photolytic and thermal conditions were applied to standard solutions. Degradant peaks were seen in acidic, alkaline and oxidative environments, but no interference with drug peaks was observed in any of the accelerated settings, showing the stability and specificity of the approach. The assay values of 100.1 and 99.8% W/W indicating that the approach is also applicable for pharmaceutical product estimation.