Thermodynamics of solutions III: comparison of the solvation of (+)-naproxen with other NSAIDs.

Naproxen was studied by classical thermoanalytical methods, namely sublimation calorimetry, solution calorimetry and the solubility method. Temperature dependence of a saturated vapor pressure was obtained and the sublimation enthalpy, deltaHsub(0) and entropy, deltaSsub(0) and their relative fraction of the total process were calculated. These parameters yielded for naproxen were compared to the respective data of other naphthalene derivatives. The crystal lattice energy of naproxen was calculated by two force fields (Gavezzotti et al. and Mayo et al.) and compared to the experimental data. Contributions of different motifs of the naproxen molecule to the total packing energy were analyzed. The Gibbs energy of solvation as well as enthalpic and entropic terms thereof in aliphatic alcohols have been studied for naproxen, and compared to model substances and other non-steroid anti-inflammatory drugs (benzoic acid, diflunisal and flurbiprofen). The major driving force of the solvation process is the enthalpy. The respective contributions of the specific and the non-specific solvation interactions in terms of absolute and relative values have been investigated.