Irritable bowel syndrome (IBS) is one of the most frequently diagnosed gastroenterological disorders and can lead to significant deterioration of quality of life and an increase in health care and societal costs. Patients with lactose intolerance are unable to fully digest lactose caused by lactose malabsorption. The undigested lactose moves into the large intestine, fermented by bacteria, and causes bloating, gas, and diarrhea symptoms. The two, most frequently used diagnostic methods are the lactose H2 breath test (LHBT) and the lactose tolerance test (LTT). The restriction of lactose input or the replacement of the lactase enzyme can lead to the relief of the symptoms. Lactose intolerance is a common disorder among patients with IBS, it is more frequent than in the general population.~There are no studies that assess the link between lactose intolerance and IBS. Our primary objective is the examination of the relationship between lactose intolerance and IBS with or without the replacement of lactase enzyme. Our secondary objectives are to compare the lactase/beta-galactosidase enzyme replacement with placebo with the evaluation of a TSS (Total symptom score), VAS (Visual Analog Scale), QoL (Quality of life) questionnaires. The other secondary outcomes are to compare the severity of baseline symptoms during and after lactose administration.~Patients diagnosed with IBS according to the Rome IV criteria will test with LTT and LHBT.~Who has positive LTT and LHBT will randomize into two groups: (1) alverine-citrate + simethicone and lactase; (2) alverin-citrate + simethicone with placebo.
Irritable bowel syndrome (IBS) is a functional gastrointestinal disease. There is no well-defined pharmacological treatment. This clinical trial is a prospective, double-blind, two-armed randomized controlled, single-center trial. It is created to examine the role of IBS in patients with lactose intolerance. IBS patients undergo lactose H2 breath test (LHBT) and lactose tolerance test (LTT). Those with positive LTT and LHBT will be randomized into two groups: alverine-citrate + simethicone and lactase group (1) or alverin-citrate + simethicone with the placebo group (2). The goal of this study is to compare the lactase enzyme with placebo in IBS patients with lactose intolerance.