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Solubility and Thermodynamic Analysis of Tenoxicam in Different Pure Solvents at Different Temperatures

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journal contribution
posted on 13.08.2015 by Faiyaz Shakeel, Nazrul Haq, Gamal A. Shazly, Fars K. Alanazi, Ibrahim A. Alsarra
The solubility data of drugs/pharmaceuticals in aqueous and organic solvents is important in pharmaceutical industries. Therefore, in this current study, the solubility of the practically insoluble drug tenoxicam (TNX) in various pure solvents, namely, water, ethyl alcohol, 1-butyl alcohol, 2-butyl alcohol, ethylene glycol (EG), ethyl acetate (EA), isopropyl alcohol (IPA), propylene glycol (PG), polyethylene glycol-400 (PEG-400) and 2-(2-ethoxyethoxy)­ethanol (Transcutol) was measured at different temperatures and atmospheric pressure. The measured solubilities of TNX were correlated well with calculated ones. The mole fraction solubility of crystalline TNX was found to be the highest in PEG-400 (9.76·10–3) followed by 2-(2-ethoxyethoxy)­ethanol (1.83·10–3), EA (6.79·10–4), EG (2.13·10–4), PG (1.94·10–4), 1-butyl alcohol (8.13·10–5), IPA (6.27·10–5), 2-butyl alcohol (6.15·10–5), ethyl alcohol (3.71·10–5), and water (4.11·10–6) at T = 298.15 K. Thermodynamic analysis indicated an endothermic and spontaneous dissolution of TNX due to positive values of standard enthalpy and Gibbs energy in all pure solvents investigated. The values of standard entropy for TNX dissolution were also observed as positive values in most of the solvents (except ethyl alcohol, 2-(2-ethoxyethoxy)­ethanol and EA), indicating an entropy-driven dissolution of TNX in most of the pure solvents investigated.