Four chemometric spectrophotometric methods for simultaneous estimation of amlodipine besylate and olmesartan medoxomil in their combined dosage form.

For determination of amlodipine besylate (AML) and olmesartan medoxomil (OLM) at the same time, four UV chemometric spectrophotometric techniques were created and tested in accordance with ICH standards. Method (I) was absorption subtraction method (ASM) using two wavelengths, one of which was of AML at 365 nm and the other was the isoabsorptive point of both drugs at 237 nm. Method (II) was ratio subtraction method (RSM) for determination of OLM at λ = 254 nm by taking the ratio spectrum and subtracting the constant values using 10 μg/mL of AML as a divisor in combination with extended ratio subtraction method (ERSM) to determine AML at λ = 239 nm using 10 μg/mL OLM as a divisor. Method (III) was dual wavelength method; the wavelengths used to determine OLM were 221 nm and 235 nm, while those used to determine AML were 246 nm and 259 nm. Method (IV) was the second order derivative (D) spectrophotometric method at 219 nm for OLM and 227 nm for AML. The proposed approaches were used to achieve linearity in the concentration range of 2-25 μg/mL for both drugs. The approaches were found to be uncomplicated, reproducible, efficient, and cost-effective as well as they were successfully used to determine the cited drugs in both laboratory samples and commercial pharmaceutical formulations.