Kinetics of digoxin stability in aqueous solution.
Digoxin hydrolysis was studied as a function of pH. Conversion of digoxin to digoxigenin was followed by high-pressure liquid chromatography and shown to proceed by the initial loss of one, two, or three sugars. The hydrolysis rate was directly proportional to parent drug concentration and hydrogen-ion activity. The individual hydrolysis rate constants of digoxin, digoxigenin bisdigitoxoside, and digoxigenin monodigitoxoside were determined by a simplex fitting procedure. Data are presented suggesting that at least some variation in the bioavailability of orally administered digoxin arises from observed variations in gastric pH; these variations influence the extent to which hydrolysis occurs and, thus, modify the composition of digoxin species available for absorption.
D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid; D004076:Digoxigenin / Q000032:analysis; D004077:Digoxin / Q000032:analysis*; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D012996:Solutions
D012996:Solutions; D004077:Digoxin; D004076:Digoxigenin