Thermodynamics is crucial for optimizing drug synthesis, developing pharmaceutical formulations and ensuring their stability, effectiveness and safety. The thermochemical properties of active pharmaceutical ingredients with the common biphenyl motif (RS-Flurbiprofen, Diflunisal, Fenbufen and Biprofen) available in the literature were collected, combined with our own complementary experimental results and evaluated. The vapour pressures temperature dependence of RS-Flurbiprofen was measured using the Knudsen effusion method, and the enthalpy of sublimation was obtained from this measurement. The enthalpy of fusion of RS-Flurbiprofen was measured using DSC. A reliable diagnostic method has been outlined to evaluate the quality of the available experimental thermodynamic data of drugs. The data previously available in the literature for RS-flurbiprofen, diflunisal and fenbufen were analysed and diagnosed as "thick". For RS-flurbiprofen, diflunisal, fenbufen and biprofen, the consistent sets of thermodynamic data were evaluated and recommended for the calculations of the pharmaceutic processes. The "paper-and-pencil" concept presented in this paper can be extended to the diagnosis of "sick" or "healthy" experimental thermodynamic data for pharmaceuticals with a structure other than profens.