Hyoscyamine (Levsin, Hyosyne, Symax, Oscimin, NuLev) and Linzess (linaclotide) are both medications used to treat conditions related to the digestive system, such as irritable bowel syndrome (IBS). However, they belong to different medication classes and have distinct mechanisms of action. Hyoscyamine is an anticholinergic medication that works by blocking acetylcholine, a chemical in the body, to relieve symptoms like stomach cramps and overactive bladder. It is available in various forms, including tablets and liquid solutions, and is taken multiple times a day. Linzess, on the other hand, is a guanylate cyclase-C (GC-C) agonist that increases fluid in the intestines to help with constipation. It is taken as a capsule once a day on an empty stomach. While hyoscyamine is available as a generic, Linzess is only available as a brand-name medication. Common side effects of hyoscyamine include dry mouth and dizziness, whereas Linzess may cause diarrhea and stomach pain.