The excretion study of 4-(5-methyl-1,3,4-oxadiazole-2-yl)-benzenesulfonamide in rats

Introduction: The 4-(5-methyl-1,3,4-oxadiazole-2-yl)-benzenesulfonamide (ODASA) is a newcarbonic anhydrase II inhibitor for open-angle glaucoma treatment, but the excretion study of this compound has not been performed yet. Aim: Calculation of excretion parameters of ODASAand its metabolites in urine and feces in rats. Materials and Methods: The ODASA excretion was investigated on 6 Wistar rats. The 1% suspension of ODASA was instilled into each eye in a volume of 20μL (1.6 mg/kg). Excreta were collected using metabolic cages. Sampling of feces was performed every 24 h for 384 h after the administration. Urine was taken frequently in first day of experiment: 4 h, 8 h and 12 h after administration. Samples was stabilized and frozen (temperature <-70°C). Quantification of ODASA, 4-[5-(hydroxymethyl)-1,3,4-oxadiazole-2-yl]-benzenesulfonamide (M1), N-hydroxy-4-(5-methyl-1,3,4-oxadiazole-2-yl)-benzenesulfonamide (M2), 4-(5-methyl-1,3,4-oxadiazole-2-yl)-benzenesulfonic acid (M3) was carried out by HPLC-ESI-MS/MS. M2 was unstable in samples, and its content was calculated by summing the concentrations of M2 and its degradation product M3. Kinetex Phenyl Hexyl column (50*4.6 mm, 2.6 µm) was used for chromatographic separation. Results: The developed bioanalytical methods for rat excreta analysis were validated in the range of 10-10000 ppb for ODASA and M1, 1-1000 ppb – for M2, and 5-5000 ppb – for M3. Part of 16.29±1.60% of the active compound was eliminated in unchanged form, 80.27±1.68% – in the form of M1, and 3.43±0.33% – in form of M2 (М±SEM). The drug is mainly excreted by renal route: 14.22±1.43% in the form of ODASA, 69.90±1.80% – in the form of M1, and 1.88±0.24% – in the form of M2 (М±SEM). The highest rate of renal excretion of the studiedcompounds was observed in period of 8-12 hours after administration. The complete elimination of ODASA was achieved through 360 h after administration. Conclusion: Most part of ODASA is eliminated in the form of M1. The main route of excretion is renal. The use of validated bioanalytical methods guaranteed reliability of the obtained data.