List of products in the National Drug Code with proprietary name levsin. Hyoscyamine is used to treat a variety of stomach/intestinal problems such as cramps and irritable bowel syndrome. It is also used to treat other conditions such as bladder and bowel control problems, cramping pain caused by kidney stones and gallstones, and Parkinson's disease. In addition, it is used to decrease side effects of certain medications (drugs used to treat myasthenia gravis) and insecticides. This medication works by decreasing acid production in the stomach, slowing down the natural movements of the gut, and relaxing muscles in many organs (such as the stomach, intestines, bladder, kidney, gallbladder). Hyoscyamine also lessens the amount of certain body fluids (e.g., saliva, sweat). This medication belongs to a class of drugs known as anticholinergics/antispasmodics.