RP-HPLC Method Development and Validation for Simultaneous Estimation of Duloxetin and Methylcobalamine in Combined Dosage Form

A simple, precise, accurate, simultaneous stability indicating RP-HPLC method for the estimation of DLU (Duloxetin) and MCB (Methylcobalamine) in combined dosage form was developed using Intersil-C18 (4.6 x 250mm, 5m) in an Isocratic mode with mobile phase comprising of Phosphate buffer (pH 4.5) The flow rate was 1 mL/ min and effluent was monitored at 255.0 nm. The retention times were found to be 5.32 min for DLU and 3.59 min for MCB. The assay exhibited a linear dynamic range of 20- 120 g/mL for DLU and 10- 60 g/mL for MCB. The calibration curves were linear (r 2 = 0.999 for DLU and r 2 = 0.999 for MCB) over the entire linear range. Mean % recovery was found to be 99.68 % for DLU and 100.3 % for MCB with % RSD was NMT 2 for both estimations which fully agrees with system suitability which is in good agreement with labeled amount of formulation. The % RSD for Intra- Day & Inter-Day Precision was NMT than 2 for both the drugs. The developed method was validated as per ICH guidelines.