Mechanisms involved in the gastro-protective effect of STW 5 (Iberogast) and its components against ulcers and rebound acidity.

The protective effect of a commercial preparation (STW 5, Iberogast), containing the extracts of bitter candy tuft, lemon balm leaf, chamomile flower, caraway fruit, peppermint leaf, liquorice root, Angelica root, milk thistle fruit and greater celandine herb, against the development of gastric ulcers was previously reported in an earlier publication (Khayyal et al., 2001). All extracts produced a dose dependent anti-ulcerogenic effect associated with a reduced acid output, an increased mucin secretion, an increase in prostaglandin E(2) release and a decrease in leukotrienes. The effect on pepsin content was not uniform and did not seem to bear a relationship with the anti-ulcerogenic activity. The best effects were observed with the combined formulation, STW 5. Furthermore, the effect of the latter in protecting against the development of rebound gastric acidity was examined experimentally in rats and compared with the effect of some commercial antacid preparations (Rennie, Talcid and Maaloxan). A model of testing rebound acidity was developed by inducing a marginal increase in gastric acidity through the administration of indomethacin, in such a way that it could be easily neutralized, allowing any eventual secondary increase in acidity to be measured within a few hours of administration. In addition, the serum gastrin level was measured after drug treatment to establish any correlation between it and any rebound acidity. The results obtained demonstrated that STW 5 did not only lower the gastric acidity as effectively as the commercial antacid, but it was more effective in inhibiting the secondary hyperacidity. Moreover, STW 5 was capable of inhibiting the serum gastrin level in rats, an effect which ran parallel to its lowering effect on gastric acid production.