The compatibilities and stabilities of some binary mixtures and generic hydrochlorothiazide formulations were studied by using
TG, DSC and a DSC-photovisual system. The kinetic parameters were determined via the Arrhenius equations. Tablet B presented
higher compatibility and thermal stability than those of tablets A and C. The photovisual system demonstrated that the decomposition
of tablet A occurs before the melting point, due to the Maillard reaction between the hydrochlorothiazide and lactose present
in the formulation. The behaviour and rate constants of binary mixtures suggest that lactose can be substituted for microcrystalline
cellulose, MC(101), in tablet A. The DSC and TG data revealed different characteristics of compatibility and stability in
generic formulations from different manufacturers.