In the present work the method of calculation of thermodynamic potentials (Gibbs free energy, enthalpy and entropy) and analysis of contribution of change of translational, rotational and vibrational degrees of freedom to the energy of heteroassociation of aromatic drug molecules with caffeine and flavin mononucleotide is developed. The obtained values of change of Gibbs energy and entropy of translational, rotational and vibrational degrees of freedom are required for complete energetic analysis of the heteroassociation reactions.