Programmed humidifying in drug stability experiments.

The stability of penicillin potassium, as a solid state model, was investigated by a programmed humidity and temperature controlled method. An optimization calculational approach to data handling is suggested. The stability of drugs which are unstable to both heat and moisture could be studied by a single pair of experiments, one with programmed humidity control and one non-isothermal, rather than many standard isothermal studies, each at constant relative humidity. The controlling system, based on a pocket computer, was found to be accurate and reliable. The results indicated that the kinetic parameters obtained were comparable to those from isothermal studies.