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Spasmolytic effects of STW 5 and its components on ileal contractions induced by acetylcholine, prostaglandin F2α and substance P
Irritable bowel syndrome (IBS) is one of the most frequent diseases in the gastroenterological practice, and phytotherapy is an option of increasing importance in actual therapy. A phytomedicine with clinically proven efficacy in this indication  is STW 5 (Iberogast®), which is used in an increasing number of countries including the USA, Australia and Canada.
As intestinal spasms are involved in the etiology of IBS , its influence and that of its components on spontaneous contractility and on contractility induced by the agonists acetylcholine (ACh), prostaglandin F2alpha (PGF2α) and substance P (SP) was tested. Concentrations ranged from 2µl/ml to 10µl/ml, those of the agonists from 0.1µM to 100µM. Effects on frequency, phasic contraction force and agonist-induced tone were evaluated.
The ileal sections exhibited a spontaneous contractile activity with an amplitude of 3.4±2.3 mN (PTyr) and a frequency of 21.6±3.7/min. Application of ACh, PGF2α and SP induced dose dependent tonic contractions. ACh decreased spontaneous contractility, while PGF2α and SP increased it. After pre-treatment with extracts from peppermint leaves, chamomile flowers, angelica root, milk thistle fruits and STW 5, contractility due to ACh and PGF2α was significantly reduced, while the frequency was influenced only to a smaller extent. When SP was applied, mainly phasic contractions, but not the tonic contractions, were inhibited by STW 5. In contrast, butylscopolamine decreased the tone, but not the spontaneous activity.
The results allow the conclusion, that STW 5 (Iberogast®) and its herbal components act antagonize contraction induced by agonists, which may play a role in intestinal spasms in IBS. In how far these effects are influenced on receptor level or on the level of mechanisms of muscular contraction, can be clarified by further studies.
References: 1. Madisch, et al. (2004) Aliment Pharmacol Ther 19:271–79 2. Ammon et al. (2006) Phytomedicine 13 SV:67–74