Influence of humidity and hydroxypropyl cellulose, hydroxypropylmethyl cellulose, glyceryl behenate or magnesium stearate on the degradation kinetics of quinapril hydrochloride in solid phase.

Catalytic effect of hydroxypropyl cellulose, hydroxypropylmethyl cellulose, glyceryl behenate and magnesium stearate in the presence of 50.9% - 76.4% humidity at 318 K on stability of quinapril hydrochloride (QHCl) was examined by HPLC method. The differences in kinetic mechanism of degradation of QHCl were observed. The effect of humidity on QHCl stability in the presence of hydroxypropyl cellulose, hydroxypropylmethyl cellulose, glyceryl behenate or magnesium stearate was linear and according to the equation ln k(i) = aRH% + b.