The daily dose of commercial extract of the drug is smaller than traditional medicine powder. However, the commercial extract tends to hygroscopic .To reduce moisture absorption of the commercial extract of Liu-Wei-Di-Huang, this study attempted to mix with low- excipient or coated with polymer. Polysaccharides were used as excipient to moisture-proof and the proportion of polysaccharides to dried extract was one to five, one to ten, one to fifteen and one to twenty. Tablets produced by using different pressure to compress freezing-dry extract were directly coated with five kinds of polymers (PVP K-10, PVP K-30, and EC). The bioequivalence was tested based on the pharmacokinetics. The concentration of paeonol and loganin were determinate by HPLC of all preparations. Results show that tablets (non-coating) and Tablet EC had higher concentration of paeonol and loganin. It was compared with the traditional medicinal powder, the pill, the tablet (non-coating) and Tablet EC. Rats were fed daily dose of the traditional medicinal powder, the pill, the tablet (non-coating) and Tablet EC.The concentration of paeonol and loganin in plasma were assayed by HPLC. Results show that the best moisture-proof product was Tablet EC using the pressure of 500 kgf/cm2 to compress and coated with ethyl cellulose. The contents of paeonol and loganin of the extract with low excipient and tablets were higher than the traditional medicine powder. Maximum absorption concentration of paeonol of Tablet EC was lower than the traditional medicinal powder, the pill and the tablet (non-coating). The time of half-life of paeonol of Tablet EC was longer than the traditional medicinal powder, the pill and the tablet (non-coating). In contrast, the absorption rate of loganin of Tablet EC was faster than the traditional medicinal powder, the pill and the tablet (non-coating). This study suggested that coating promoted the commercial extract of Chinese medicine to be more stable and fineness and achieved the goal of taking medicine conveniently .
