Programmed Humidifying Drug Stability Experiments

Studying the effect of relative humidity and temperature on the drug stability is of great theoretical and practical importance in enhancing the drug stability, providing reasonable shelf condition and estimating the drug's shelf life. However, due to the complexity of testing method and skills, studies at home and abroad, both in theories and practice, on the effect of humidity on the drug stability, are not as much as that on thermo degrading reaction.At present, traditional constant temperature and humidity drug stability experiment is widely adopted in this kind of studies. In the studies on the effect of heating on the drug stability, programmed heating drug stability experiment saves more times than the constant temperature experiment, which reminds us that in the studies on the effect of humidity, this might be feasible in the test by continuously changing the relative humidity according to certain rules. In the theoretical analysis, two experiments can be adopted to take the place of numbers of tests, namelyprogrammed heating experiment to obtain the kinetics parameter related to temperature and programmed humidifying experiment to obtain the kinetics parameter related to humidity.Program controlled humidity and temperature oven has been used to programmed humidity and temperature. In the case of penicillin potassium, all the kinetic parameters were obtained by programmed humidifying and programmed heating experiments.Constant humidity and temperature experiments indicate that thedc degradation kinetic can be expressed as-----= k(cQ -c + 0.00048), where,dt the k can be expressed by humidity and temperature ask = y4exp(jwi?//)exp(----—) ? The relationship between content and time atRTconstant temperature by linear humidifying RH = RH0 -0.08/ is expressed as[ln(c0 - c + 0.00048)- In0.00048] = Aexp(----^){-----—exp(mRH0 )[exp(-0.08mO -1]} ■RT 0.08/wAnalyzing the data from experiments, m and -Aexp(----—) were obtainedRTby linear regress [ln(c0 - c + 0.00048) - In0.00048] to{--------exp(mJy/0)[exp(-0.08jM/)-l]}. The relationship between content and0.08mtime at constant humidity by reciprocal heating--------= -6xlO~7f isTo Texpressed as[ln(c0 -c + 0.00048) - In0.00048] = A exp(mRH){--------^—exp(—^-)[exp(-6xl° ￡°f -1]}.6 x 10 Ea RT0 RAnalyzing the data from experiments, Ea and Aexp(mRH) were obtained by linear regress [m(c0 - c + 0.00048) - In0.00048] to& , Ea u , 6x\0'n E J , . , , , . . .-exo(-----^)FexD(---------------—11! ? A can be calculated bypv _ v\ R iipsimultaneous equations from m andy4exp(-----—) obtained by programmedRThumidifying experiment at constant temperature and Ea and Aexp(mRH) obtained by programmed heating experiment at constant humidity.Simulate experiments obtained by Basic language programs show that programmed humidifying and heating experiments are feasible.