Gastrointestinal Absorption Of Drugs (Carbamazepine –Cbz): In Vivo - In Vitro Correlations Using A Commercial Absorption Simulator

Abstract

The rate of intestinal absorption of carbamazepine (CBZ) was studied using the Sartorius Absorption Simulator. Diffusion rate constants (kd) of 7.43 (±0.32) x 10-3 cm.min-1 and 7.44 (±0.2) x 10-3cm.min-1 were obtained using Sörensen phosphate buffer pH 7.5 and the same buffer containing 0.4% BSA respectively as simulated plasma. These kd values were converted into absorption rate constants (Ki) of 7.43 x 10-2min-1 and 7.44 x 10-2 min-1 (for humans, G-factor 10) and 3.34 x 10-2min-1 and 3.35 x 10-2min-1 (for rats, G-factor 4.5). These results show that the presence of 0.4% BSA in the artificial plasma produces no apparent difference in the diffusion process. A correlation was also made between the simulated absorption rate constant (Ki) from this in vitro method and that obtained from an in situ rat gut technique, 5.29±0.8min-1 or 3.23±0.79min-1g-1 (as per dry weight of the gut). These results thus suggest that the measurement of diffusion rates through artificial membranes could be a useful predictive tool for the assessment of the availability in man of new lipophilic compounds.

Keywords: Intestinal absorption, sartorius absorption simulator, carbamazepine

Global Journal or Pure and Applied Sciences Vol. 14 (4) 2008: pp.401-406