Development and Validation of UV-Spectrophotometric, Spectrofluorimetric methods for simultaneous estimation of Memantine Hydrochloride and Donepezil Hydrochloride using OPA - B mercaptoethanol Derivatization in tablet dosage form and human plasma

Abstract

This paper describes validated UV spectrophotometric, spectrofluorimetric methods for the simultaneous estimation of memantine hydrochloride (MEM) and donepezil hydrochloride (DH) in bulk and combined tablet dosage form and spectrofluorimetric method for estimation of MEM and DH in human plasma. The proposed methods include derivatization of MEM with OPA-βmercaptoethanol due to lack of chromophoric group. UV Spectrophotometric method includes simultaneous equation method that involves measurement of absorbance at two wavelengths i.e. at 337 nm (λmax of MEM) and 312.6 nm (λmax of DH) in methanol. Linearity range was observed in the concentration range 5-80 μg/mL with R2 0.9984 and 0.9987, respectively for MEM and DH. LOD and LOQ were found to be 1.220 & 3.698 μg/mL for MEM respectively and 0.775 & 2.347 μg/mL for DH respectively. Spectrofluorimetric method includes synchronous spectrum method using delta value 65 (low sensitivity mode) that involves measurement of fluorescence intensity at two wavelengths in synchronous spectra of drugs i.e. at 450 nm for MEM and 361 nm for DH in borate buffer. Linearity range was observed in the concentration range 1-30 μg/mL for both the drugs with R2 0.9986 and 0.9983, respectively for MEM and DH. LOD and LOQ were found to be 0.228 & 0.691 μg/mL for MEM, respectively and 0.135 & 0.410 μg/mL for DH, respectively. For estimation of MEM & DH in human plasma extraction was carried out using 5% TCA for protein precipitation followed by liquid-liquid extraction with 5% IPA in n-Hexane. Under spectrofluorimetric conditions delta value 65 applied in synchronous mode (medium sensitivity mode) and wavelength used in analysis were 389 nm and 420 nm respectively for MEM and DH. Linearity range was observed in the concentration range 5-105 ng/mL and 50-300 ng/mL for DH and MEM with R2 0.9965 and 0.9951, respectively. Percentage recovery was found to be 74.43%-83.33% and 77.85%-83.68%, for MEM and DH, respectively.