Improved Spectrophotometric Estimation of Nimodipine in the Pharmaceutical Formulation and Biological Fluids

Abstract

Nimodipine (NDP) belongs to the class of pharmacological agents known as calcium channel blockers. It is used to treat symptoms resulting from a ruptured blood vessel in the brain (hemorrhage). NDP increases blood flow to injured brain tissues. For its clinical importance, a sensitive, accurate and simple spectrophotometric approach for the evaluation of NDP in bulk, tablet and biological fluids has been developed. The procedure involves the reaction of the reduced NDP with equimolar nitrous acid then followed by coupling with the available γ-resorsolic acid reagent in a basic solution to give a colored azo dye. The resulting azo dye is soluble in water and shows a maximum absorption peak at 436 nm. All the variables which affect the conditions such as the influence of acid, γ-resorsolic acid and alkali concentrations, reaction time and Beer׳s law limits were studied carefully and adjusted. The optimal conditions showed the color of azo-dye was stable for more than 1 h. The method was found linear in the range from 1.0 to 40 µg/mL with a good value of determination coefficient (R2= 0.9988). The molar absorptivity was calculated and set up to be 1.8495x104 L/mol.cm. The detection limits and quantitation limits were also estimated and found to be 0.0059 and 0.0195 µg/mL, correspondingly. The approach was established by estimating NDP in pharmaceutical tablets and biological fluids. The precision (RSD) was calculated to be better than 0.324%, whereas the values of recovery percent and relative errors were in the range of 97.95% to 99.08 % and -3.78% to 2.22%, respectively, without interfering from any common excipients present in the samples. The nature of the yellow dye has been studied between diazotized NDP and γ-resorsolic acid reagent and was equal to 1:1.

Keywords

• nimodipine
• γ-resorsolic acid
• diazo-coupling