Flavoxate and 3-methylflavone-8-carboxylic acid. Assay methods in blood and urine, plasma-red cells repartition and stability.
The following assay methods for pharmacokinetic studies on flavoxate (F) and on its main metabolite, i.e. 3-methylflavone-8-carboxylic acid (A), are described. 1. Spectrophotometry for the assay of F and of A in plasma, 2. TLC-Spectrodensitometry and GLC for the assay of A in urine after acid hydrolysis, 3. TLC-Spectrodensitometry for determining the F : A ratio in plasma or in urine. It was found that F hydrolyzes into A. This process depends on the pH and on the medium. In water, at pH 5.0, F is stable, while in phosphate buffer at pH 7.4 the semi-hydrolysis time is 60 min. In a solution with bovine serum albumin, in rat, rabbit, dog or human plasma the semi-hydrolysis times are between 5 and 60 min. Finally the plasma-red cells repartitions of F and of A were studied in vitro in rat, rabbit, dog and human blood and found between 0.8 and 2.0 for F and between 2.1 and 4.6 for A.
D000818:Animals; D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D003720:Densitometry; D004285:Dogs; D004355:Drug Stability; D005419:Flavonoids / Q000032:analysis* / Q000097:blood / Q000652:urine; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D008722:Methods; D010880:Piperidines / Q000097:blood / Q000652:urine; D011817:Rabbits; D051381:Rats; D013045:Species Specificity; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
D005419:Flavonoids; D010880:Piperidines