The thermal curves and the enthalpy changes of the interaction between some oral sustained release preparations (Contac, Fenbid
and Benza sustained release capsules) and physiological saline have been measured at 298.15 K with a MS-80 standard Calvet
microcalorimeter. The curves that recorded the changes of heat effect with time have clearly shown the sustained release action
and process of the above preparations. A method for examining the sustained release action of sustained release preparations
can be developed from the above experiments. The principle of application and the experimental procedure of this method have
been expounded, and some results of the above experiments have also been discussed.