[Evidence-based medicine and phytotherapy for functional dyspepsia and irritable bowel syndrome: a systematic analysis of evidence for the herbal preparation Iberogast].

Functional gastrointestinal disorders like functional dyspepsia and irritable bowel syndrome are characterized by more or less specific symptoms and the absence of structural lesions to explain symptoms. Other studies suggest that abnormalities of specific gut function are linked to manifestation of symptoms. These abnormalities include disturbances of motility such as postprandial fundic relaxation, gastric emptying and disturbed visceral sensory function. The underlying pathophysiology is not fully understood. However, various studies point towards hereditary (or molecular) factors modified by environmental factors. Considering this broad spectrum of factors it is conceivable that treatments targeting a single mechanism are most likely to improve symptoms only in patients with a disturbance linked to this mechanism. Thus overall efficacy in the whole patient population is limited. Indeed, superiority of chemically defined treatments targeting a single receptor yield a benefit over placebo of between 10 and 15%. In recent years well-controlled studies have demonstrated superiority of specific herbal preparations. This in particular held true for combinations of various plant extracts or herbal extracts with a number of different active ingredients. However, efficacy of herbal treatment for functional GI disorders cannot be taken for granted and these drugs need to be rigorously tested for efficacy and safety. In this context, same standards apply as for conventional chemically defined medications.