Drug used in irritable bowel syndrome with constipation is?
**Core Concept**
Irritable bowel syndrome with constipation (IBS-C) is a subtype of irritable bowel syndrome characterized by abdominal pain and constipation. The management of IBS-C involves medications that alter bowel habits, relieve pain, and improve quality of life.
**Why the Correct Answer is Right**
Linaclotide is a guanylate cyclase-C agonist that increases intestinal fluid secretion and bowel motility, thereby alleviating constipation. It acts by stimulating the guanylate cyclase-C receptor, which leads to the activation of adenylate cyclase and the subsequent increase in cyclic guanosine monophosphate (cGMP) levels. The elevated cGMP levels result in the activation of chloride channels, leading to increased intestinal fluid secretion and relief of constipation.
**Why Each Wrong Option is Incorrect**
**Option A:** Lubiprostone is a chloride channel activator that increases intestinal fluid secretion, but it is more effective for treating IBS-D (diarrhea-predominant irritable bowel syndrome) than IBS-C.
**Option B:** Alosetron is a 5-HT3 receptor antagonist that slows intestinal motility and is used for treating severe diarrhea-predominant IBS, not constipation.
**Option C:** Loperamide is an opioid receptor agonist that slows intestinal motility and is used for treating diarrhea, not constipation.
**Clinical Pearl / High-Yield Fact**
When choosing a medication for IBS-C, consider the mechanism of action, as some medications may exacerbate constipation or worsen symptoms.
**Correct Answer: C. Linaclotide**