TENOKSİKAM, PİROKSİKAM VE MELOKSİKAM’IN pKa DEĞERLERİNİN RP-HPLC YÖNTEMİYLE 25℃ VE 37℃’DE THF-SU İKİLİ ORTAMINDA TAYİNİ

Abstract

Objective: In this study, the ionization constant (pKa) values of oxicam group drug active ingredients, tenoxicam, piroxicam and meloxicam, were investigated both because of their effectiveness in reducing pain and inflammation and because of their pharmaceutical importance. Material and Method: pKa values were determined by RP-HPLC method in tetrahydrofuran-water binary mixture (30%-40%(v/v)) at 25 °C and 37 °C. The pKa values of these compounds in water were evaluated by mole fraction and Yasuda-Shedlovsky extrapolation methods.Result and Discussion: This study is the first pKa determination study for tenoxicam, piroxicam and meloxicam in tetrahydrofuran-water media and also at 37 ℃, which is body physiological temperature. For tenoxicam, piroxicam and meloxicam, the pKa values calculated by the mole fraction method at 25 °C were 5.067 ± 0.037; 5.237 ± 0.065; 4.027 ± 0.144; pKa values at 37 °C are 5.166 ± 0.017; 5.197 ± 0.084; 4.161 ± 0.116. By Yasuda-Shedlovsky extrapolation, pKa values calculated at 25 ℃ were 5.061 ± 0.035; 5.232 ± 0.063; 4.021 ± 0.141; pKa values at 37 ℃ are 5.161 ± 0.013; 5.192 ± 0.053; 4.155 ± 0.094. The results are in agreement with previous studies with different methods and different solvents at 25 °C.