Basic Study on Development of Glycyrrhizin Formulations for Self Administration

Abstract

The aim of this study was to develop glycyrrhizin (GZ) dosage forms which can be self administered, such as intranasal solutions and pen-type subcutaneous injections. We found that the use of L-arginine and L-histidine as pharmaceutical adjuvants helped inhibit gel formation by GZ, and the optimal formulation was a GZ solution (400 mg/mL) prepared using a 20 mM phosphate buffered solution (pH 7.4) containing 4% L-arginine and 4% L-histidine. The apparent phase behavior and GZ content of this GZ formulation did not change for at least 2 weeks when kept at 4°C and 60°C. After intranasal and subcutaneous administration (50 mg/kg) to rats, the bioavailability of glycyrrhizin was 17% and 77%, respectively. These results suggested that the subcutaneous administration of our highly concentrated GZ solution is a useful substitute for commercial GZ products that are administered intravenously.