Abstract

The thermodynamic parameters of the inclusion complexation interaction of piroxicam and beta-cyclodextrin have been evaluated. Inclusion complexes of piroxicam and beta-cyclodextrin were produced by different methods such as physical mixture, kneading, coprecipitation, evaporation and heating under reflux. X-ray powder diffraction (XRPD) studies confirmed formation of inclusion complexes between piroxicam and beta-cyclodextrin. Positive Gibb’s free energy (ΔG) values were obtained for all the inclusion complexes of piroxicam and beta-cyclodextrin suggesting that the interaction is favoured in non-spontaneous process (-that is, the process led to a decrease in the free energy of the system). The higher value of ΔG obtained at higher temperatures may be related to the surface vibration, as the temperature increases. The enthalpy (ΔH) values calculated for the beta-cyclodextrin - piroxicam inclusion complexation interaction were all negative as well as the ΔS values. All these indicate that the interaction were exothermic and spontaneous and is highly favoured and beta-cyclodextrin could be utilized in the complexation of piroxicam for increased solubility and stability.

Key words:  Beta cyclodextrin, piroxicam, XRPD, inclusion complex, energetics, interaction, stability.