Influence of light and temperature on the stability of procaine hydrochloride injection / 药学学报

ABSTRACT

<p><b>AIM</b>To study the influence of light and heat on the stability of procaine hydrochloride injection.</p><p><b>METHODS</b>Accelerated tests upon exposure to light at high temperatures were employed.</p><p><b>RESULTS</b>In experiments with either isothermal heating or exposure to light at high temperatures, the drug degradation rate obeys first-order kinetics. The total rate constant, ktotal, caused by both light and heat can be divided into two parts ktotal = kdark + klight, where kdark and klight are the rate constants caused by heat and light, respectively. The klight can be expressed as klight = Alight x E x exp(-Ea,light/RT). Where E is the illuminance of light, Alight is an experimental constant related to light sources, and Ea,light is an experimental constant.</p><p><b>CONCLUSION</b>Because the form of klight is similar to the Arrhenius equation, it is suggested that Ea,light might be the observed activation energy of the rate-determining step of the subsequent processes of the photochemical reaction. This viewpoint is supported by the fact that the Ea,light is independent of light sources.</p>