Validation of an HPLC Method Devised for the Quantitative Determination of Ropivacaine in Drug-Delivery Systems

Abstract

Ropivacaine (RVC) is a long acting local anesthetic, synthesized in the S enantiomeric form. This work describes the development of an analytical method and validation parameters that assured acceptable characteristics (suitability, reliability and feasibility) to quantify RVC in the presence of drug-delivery carriers such as cyclodextrins and liposomes. High performance liquid chromatography (HPLC) was performed using a reversed-phase C18 column, a mixture of acetonitrile and phosphate buffer pH 8.0 (60:40, v: v) as the mobile phase, 1.2 mL/min flow rate and oven temperature of 30 °C; Ropivacaine was detected by UV absorption, at 240 nm. The results showed that the analytical method is accurate, reproducible, robust and linear over the concentration range of 0.08-1.16 mM RVC. The method was applied to detect the in vitro release profile of the anesthetic loaded in two different drug-delivery systems: i) RVC encapsulated into egg phosphatidylcholine liposomes, and ii) RVC complexed with hydroxypropyl-beta-cyclodextrin (HP-βCD). The release kinetics rate was significantly slower for the RVC-HP-βCD complex than for liposomal RVC or the free drug (RVC in solution). To explain that, diffusion ordered spectroscopy (1H-NMR DOSY) experiments were conducted. The results confirmed the stronger interaction of the anesthetic with HP-βCD (association constant, Ka = 128 M-1) than with liposomes (Ka = 22 M-1), in accordance with the release kinetic data. In conclusion, the HPLC method described was proven suitable for the quantification of ropivacaine in drug-delivery systems.