SN instructed patient about Linzess (linaclotide) which is indicated in adults for the treatment of irritable bowel syndrome with constipation. It can cause serious side effects, including diarrhea, the most common side effect, which can be severe. Diarrhea often begins within the first 2 weeks of treatment. Stop taking Linzess and call your doctor asap if you get severe diarrhea during treatment with Linzess. Other common side effect may include gas, stomach-area (abdominal) pain, swelling, or a feeling of fullness or pressure in your abdomen (distension). Tell your doctor if you have any side effect that bothers you or that does not go away. Call your doctor or go to the nearest hospital emergency room right away if you develop unusual or severe stomach-area (abdominal) pain, especially if you also have bright red, bloody stools or black stools that look like tar.