The interaction of theophylline with benzylamine in aqueous solution was studied by the solubility method and by proton nuclear magnetic resonance (1H-NMR) spectroscopy. The results show that two types of intearctions, ion pair and stacking, occur between theophylline and benzylamine. Apparent stability constants for the formation of complexes of the ion pair type and stacking type were estimated approximately at 25°C.
