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

<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>

Effect of light and heat on the stability of furacilin aqueous solution / 药学学报

<p><b>AIM</b>To study the effect of both light and heat on the stability of furacilin aqueous solution and the probability of substituting for isothermal accelerated tests by nonisothermal accelerated tests upon exposure to light at high temperatures.</p><p><b>METHODS</b>The isothermal and nonisothermal accelerated tests were employed. The accelerated tests were proceeded in the dark and exposed to light at high temperature. Tungsten, ultraviolet and fluorescent lamps were employed in exposure tests.</p><p><b>RESULTS</b>The degradation of furacilin aqueous solution in isothermal heating experiments or the exposure experiments to light at high temperatures obeys zero-order kinetics. The total degradation rate constant k caused by both light and heat can be divided into two parts: k = kdark + klight, where kdark and klight are the degradation rate constant caused by heat and light, respectively. The klight can be expressed as klight = Alight.exp(-Ea,light/RT).E, where E is the illuminance of light; Alight and Ea,light are both experimental constants. The parameters obtained in nonisothermal accelerated tests were comparable to those obtained in classic isothermal accelerated tests.</p><p><b>CONCLUSION</b>Nonisothermal accelerated tests may substitute for isothermal accelerated tests during the study of the effects of both light and heat on the stability of drugs, in order to save time, labor and drugs.</p>