In the present paper, we report the thermodynamics of the four amphiphilic drugs (two antidepressants, amitriptyline hydrochloride and imipramine hydrochloride, and two phenothiazines, chlorpromazine hydrochloride and promethazine hydrochloride) in the presence of additives [NaCl, cetyltrimethylammonium bromide (CTAB), polyethylene glycol t-octylphenyl ether (TX-100)] and evaluated Gibbs energies [at the air/water interface (G(min)((s))), the standard Gibbs energy change of micellization (Delta(mic)G(0)), the standard Gibbs energy change of adsorption (Delta(ads)G(0)), and the excess free energy change of micellization (Delta G(ex))].