Abstract

PENA, M. Ángeles; ESCALERA, Begoña  and  TORRES, Norma. Thermodynamic analysis of celecoxib in amphiprotic and amphiprotic-aprotic solvent mixtures at several temperatures. Rev. colomb. cienc. quim. farm. [online]. 2019, vol.48, n.3, pp.528-546.  Epub Oct 29, 2020. ISSN 0034-7418.  https://doi.org/10.15446/rcciquifa.v48n3.84957.

The solubilities of celecoxib (CLX), a COX-2 selective nonsteroidal anti-inflammatory drug, were determined in water-ethanol and ethanol-ethyl acetate mixtures at several temperatures (288.15-308.15 K). The solubility curves as a function of ethanol ratio were studied at five temperatures, they showed a single maximum located at 50% ethanol-ethyl acetate (δ1 = 22.50 MPa1/2). The measurements of the variation of inherent drug solubility with temperature were used to estimate different thermodynamic parameters, enthalpy, entropy and Gibbs free energy of solution (ΔH S , ΔS S and ΔG S hm , respectively). The apparent enthalpies of the solution were a nonlinear function of the ethanol ratio in aqueous mixture. Non-linear enthalpy-entropy compensation analysis was observed indicating different dissolution mechanism with the variation in mixtures composition. The solubility enhancement is entropy driven at water-rich region (0-40% v/v ethanol) and enthalpy controlled at ethanol-rich region (40-100% v/v ethanol), likely due to water-structure loss around nonpolar moieties of the drug and for the ethanol-rich mixtures it is the enthalpy, probably due to the drug better solvation.

Keywords : celecoxib; solubility; solvent mixtures; thermodynamic quantities; characterization.

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