Release kinetics of tramadol hydrochloride from solid drug formulations

Abstract

The aim of this paper is to present the use of a reaction and a dissolution kinetic approach for evaluating the dissolution profile of a drug. As model substances, two controlled-release formulations (with different type of matrix) with tramadol hydrochloride were chosen. Release kinetics of tramadol hydrochloride was studied at isothermal conditions (37 °C) and at different pH values for media used for dissolution. The dissolution profiles obtained by using HPLC with UV detection were fitted by the first-order kinetic model, Korsmeyer–Peppas, Higuchi, and Weibull models. The main results of regression analysis were the determination of the first-order release rate constant (k1), the release exponent (n) from Korsmeyer–Peppas model, Higuchi constant (KH), and the parameters of Weibull model (b, λ).