Novel two-step release system for the traditional Chinese medicine compound Danshen

A novel two-step release system for the traditional Chinese medicine compound Danshen was developed by combining an effervescent osmotic pump tablet (EOPT) and a pulsed-released tablet (PT) of compound Danshen into one hard capsule. The EOPT of Danshen was prepared with sodium chloride, mannitol, hydroxypropylmethylcellulose (HPMC), and sodium bicarbonate as osmotic agents. The osmotic pressure from EOPT was greatly enhanced by carbon dioxide generated from the reaction between sodium bicarbonate and acidic components from Danshen. It was shown that the tested Danshen components could be completely released from the prepared EOPT following a zero-order release for up to 12 h. The PT of compound Danshen was a three-layer coated tablet composed of organic acid and osmotic agents. Eudragit RL, HPMC and the mixture of EC and Eudragit RS, RL were the major constituents of the separation layer, swelling layer and controlling release membrane, respectively. The swelling test of the PT indicated that swelling is a prerequisite for drug release from this PT device. In addition, the swelling behavior further suggested the drug release mechanism of PT involves diffusion, the osmotic pumping effect, and organic acid-induced effect, among which the osmotic pumping effect was the most important. Moreover, there was no significant difference among the five active constituents in their release profiles from the final combined two-step release system of compound Danshen.