Solubility enhancement of nimodipine using mixed hydrotropic solid dispersion technique

Abstract

Background and objective: Low aqueous solubility of active pharmaceutical ingredients has an effect on both formulation development and bioavailability. Nimodipine is an antihypertensive agent with low oral bioavailability, which might be attributed to the extremely poor water solubility. This study aimed to increase the solubility of nimodipine in water using hydrotropes and solid dispersion technology to increase dissolution rate compared to the marketed drug product. Methods: Solubility of nimodipine was determined separately in sodium acetate, sodium citrate, sodium benzoate, and niacinamide solutions at a concentration of 10, 20, 30, and 40% w/v using distilled water as a solvent. The highest solubility was obtained in 40% sodium benzoate solution. Mixed concentrations of hydrotropic agents were used in ratio 1:3 (niacinamide: sodium benzoate). Fourier-transform infrared spectroscopy was used to exclude any drug-hydrotropes interaction. The dissolution rate of nimodipine from solid dispersion and physical mixture were studied using USP type II dissolution test apparatus in acetate buffer (pH 4.5) as a dissolution media. Results: Hydrotropic solid dispersion of nimodipine with a blend (30% sodium benzoate and 10% niacinamide) increased the dissolution rate of the drug by 1.5 folds compared to the marketed conventional nimodipine tablet. Fourier-transform infrared analysis did not show any physicochemical interaction between drug and carriers in solid dispersion formulation. Conclusion: The hydrotrop is a novel and safe compound. It is a successful way to enhance the solubility of poorly aqueous soluble drugs. Immediate dissolution of practically insoluble drug nimodipine in dissolution media indicates that it has a great potential to solubilize the drug in biological fluids. Thus, a considerable improvement in bioavailability and onset of action of the drug can be predictable. Adding of a hydrotropic agent with nimodipine in solid dispersion increased the dissolution rate of the drug compared to the marketed conventional nimodipine tablet Keywords: Hydrotropes; Nimodipine; Solubility enhancement; Solid dispersion.