Acta Pharm. 51 (2001) 139-145
A demostration of the possible intermolecular interaction between caffeine and paracetamol is presented. The influence of intermolecular association on the solubility, transmembrane permeation and phase partitioning of paracetamol was examined under different aqueous conditions. The results showed a general increase in the solubility of paracetamol in the presence of caffeine. The effect of the interaction on the transmembrane transport of paracetamol was clearly discernible under the alkaline conditions and in distilled water. Under acidic conditions, the transmembrane permeation rate of paracetamol was not as much influenced by caffeine as in distilled water or alkaline conditions. Furthermore, the effect of the association on the phase partitioning of paracetamol was measurable in the all three media used. By means of the permeation rate data, it was possible to establish that the interaction was based on a 1:1 stoichiometry.
Keywords: caffeine, paracetamol, intermolecular interaction, physicochemical properties