Characteristics of intestinal absorption and disposition of glycyrrhizin in mice

As basic studies to apply an intestinal pressure-controlled colon delivery capsule (PCDC) for glycyrrhizin (GZ), the characteristics of intestinal abs orption and disposition of GZ were investigated in mice. In the in vivo stu dy, after intravenous (iv) administration of GZ, 10 mg/kg dose, plasma GZ d isappeared from the systemic circulation with t(1/2(alpha)) of 0.0063 h, th ereafter, it slowly declined with t(1/2(beta)) of 15.23 h. The area under t he plasma drug concentration Versus time curve (AUC) values of iv (10 mg/kg ), intracolonic (50 mg/kg) and intraduodenum (50 mg/kg) administrations wer e 115.1, 16.7 and 2.7 mu gh/mL, respectively. The AUC values of plasma glyc yrrhetic acid (GB)I a degradation product after intracolonic and intraduode num administrations were 2.8 and 8.4 mu gh/mL, respectively. Inthe in situ closed loop study, the concentrations of GZ in plasma and liver after intra colonic administration were significantly increased (p < 0.05) in compariso n with those after intrajejunum or intraileum administration, while the con centration of GA in plasma and Liver after intracolonic administration had trends to increase. These observations clearly suggest that the intracoloni c administration is a useful way to improve the oral bioavailability of GZ and to enhance its pharmacological efficacy. These pharmacokinetic results of GZ suggest that GZ is a subject drug to be applied for the PCDC system w e previously developed. The PCDCs formulation of GZ will enable us to carry GZ to the colon and enhance the oral bioavailability of GZ. Copyright (C) 2000 John Wiley & Sons, Ltd.