IngentaConnect Bioavailability of glycyrrhizin from Shaoyao-Gancao-Tang in laxat...

Authors: Goto, Emi¹; He, Ju-Xiu¹; Akao, Teruaki²; Tani, Tadato³

Source: Journal of Pharmacy and Pharmacology, Volume 57, Number 10, October 2005 , pp. 1359-1364(6)

Abstract:

Shaoyao-Gancao-Tang (SGT), a traditional Chinese formulation composed of Shaoyao (Paeoniae Radix) and Gancao (Glycyrrhizae Radix), is frequently used in conjunction with laxatives such as sodium picosulfate in colonoscopy to relieve abdominal pains. We have investigated the alterations of the bioavailability of glycyrrhizin when SGT was co-administered with sodium picosulfate and we tried to identify a regimen that might minimize the alterations. Glycyrrhizin is one of the active glycosides in Gancao and SGT and is hydrolysed into the bioactive metabolite, 18-glycyrrhetic acid (GA) by intestinal bacteria following oral administration. We found that the maximum plasma concentration (C_max) and the area under the mean concentration vs time curve from zero to 24 h (AUC_{0–24 h}) of GA from a single dose of SGT administered 5 h after a single pretreatment with sodium picosulfate were significantly reduced to 15% and 20% of the control level in rats, respectively. These reductions were still significant four days after sodium picosulfate pretreatment, but were restored by repetitive administration of SGT following sodium picosulfate pretreatment. Similar reductions and recovery were observed for the glycyrrhizin-metabolizing activity of intestinal bacteria in rat faeces. The results warrant clinical studies for co-administration of laxatives such as sodium picosulfate and SGT.

Document Type: Short communication

DOI: 10.1211/jpp.57.10.0016

Affiliations: 1: Institute of Natural Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan 2: Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan 3: Institute of Natural Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan; 21st Century COE Program, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan

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Bioavailability of glycyrrhizin from Shaoyao-Gancao-Tang in laxative-treated rats