Hyoscyamine is an anticholinergic medication used to treat gastrointestinal disorders which include irritable bowel syndrome (IBS), peptic ulcers, and spasms in the stomach, intestines or bladder. Since hyoscyamine is available in a sublingual dosage form, it works quickly to alleviate symptoms. This medication reduces stomach acid production, slows the natural movements of the digestive tract by relaxing the muscles.