STW 5 (
Iberogast) is a fixed combination of nine medicinal plant extracts effective in the treatment of functional
dyspepsia and
irritable bowel syndrome. The effects of STW 5, a combination of Iberis amara fresh
plant extract, and other eight
plant extracts as well as single extract components including extracts from Menthae piperitae folium, Matricariae flos and Liquiritiae radix, were assayed in guinea pig ileum with or without stimulation with
acetylcholine or
histamine, in order to find a possible effect on the contractility of intestinal smooth muscle. STW 5 decreased
acetylcholine- and
histamine-induced contraction of guinea pig ileum. This was also true for extracts of Menthae piperitae folium, Matricariae flos and L. radix. Extract from I. amara, however, showed no
spasmolytic action; in contrary, it increased the basal resting tone and contraction of atonic ileal segments. This was also true when STW 5 was employed. A
spasmolytic action of STW 5 could also be observed in duodenum, jejunum and colon. These data are the first to show not only the
spasmolytic effects of STW 5 and its component extracts in intestinal muscle but also the tonicising effects of STW 5 through its component Iberis amara extract in relaxed intestinal muscle. Thus, pharmacological evidence suggests a dual-action principle and may explain, at least in part, the clinically observed therapeutic efficacy of STW 5 (
Iberogast) in both hypotonic and
spastic dysmotility symptoms of functional
dyspepsia and
irritable bowel syndrome.