To inhibit the ototoxicity of gentamicin (GM) and overcome the drawback related to chitosan (CS) nanoparticles preparation in acid solution, O-carboxymethyl chitosan (O-CMC) nanoparticles loaded with GM and salicylic acid (SA) were prepared by ionic cross-linking method using calcium chloride as crosslinking agent. The Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were used to analyze the reaction of O-CMC and crosslinking agent. The parameters of preparation of the compound nanoparticles including the concentration of O-CMC, the mass ratio of O-CMC to calcium chloride, and the feed ratio of SA to GM were investigated. The results showed that the obtained nanoparticles had a high zeta potential and drug-loading capacity. The nanoparticles were characterized by a spherical morphology, with average size ranging from 148 to 345 nm and a narrow particle size distribution. In vitro release studies in phosphate buffer saline (pH 7.4) evidenced a burst release in the first 1 h, followed by a sustained release in the residual time. The release amount of SA and GM were approximately equal in 24 h, which indicated that the SA- and GM-loaded O-CMC nanoparticles are a promising carrier system for inhibiting the ototoxicity of GM. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1684-1689, 2012