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approvedGI & Metabolic

Linaclotide

Also known as: Linzess, Constella, MD-1100

Linaclotide is a 14-amino-acid synthetic peptide that acts as an agonist of guanylate cyclase-C (GC-C) receptors on the luminal surface of intestinal epithelial cells. FDA-approved in 2012 as Linzess, it is a first-in-class treatment for irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC). Linaclotide works locally in the gut with minimal systemic absorption, stimulating chloride and bicarbonate secretion into the intestinal lumen to increase fluid and accelerate transit. Its active metabolite also reduces visceral pain signaling, addressing both constipation and abdominal pain in IBS-C.

3 cited references·5 researched benefits

Quick Answer

Linaclotide (Linzess) is a 14-amino-acid guanylate cyclase-C (GC-C) agonist FDA-approved for irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC). It acts locally on intestinal epithelial cells to increase fluid secretion and accelerate transit while reducing visceral pain through extracellular cGMP signaling. With minimal systemic absorption, it has an excellent safety profile. Clinical trials show significant improvement in bowel movements, bloating, and abdominal pain.

Key Facts

Mechanism
Linaclotide is a synthetic 14-amino-acid peptide with three disulfide bonds that structurally mimics the endogenous peptides guanylin and uroguanylin. It binds GC-C receptors on the apical (luminal) surface of intestinal epithelial cells, activating intracellular cGMP production. Elevated intracellular cGMP activates CFTR chloride channels, driving chloride and bicarbonate secretion into the intestinal lumen, followed by passive water movement (osmotic effect). This increases luminal fluid volume, softens stool, and accelerates intestinal transit. Separately, cGMP is exported to the extracellular/submucosal space where it inhibits nociceptive afferent nerve firing, reducing visceral hypersensitivity and abdominal pain — a critical benefit for IBS-C. Linaclotide is minimally absorbed (<0.1% bioavailability) and is degraded to its active metabolite (des-Tyr linaclotide) in the GI tract, which retains GC-C agonist activity.
Research Status
approved
Half-Life
Minimal systemic exposure (acts locally in the GI tract; luminal degradation half-life ~3 hours)
Molecular Formula
C₅₉H₇₉N₁₅O₂₁S₆
Primary Use
GI & Metabolic
Table of Contents

Benefits

  • IBS-C symptom relief — significantly improves complete spontaneous bowel movements (CSBMs), abdominal pain, bloating, and straining (phase 3 trials)strong
  • CIC treatment — increases CSBMs from ~0.2/week to ~3/week in CIC patients, with sustained efficacy over 26 weeksstrong
  • Visceral pain reduction — extracellular cGMP inhibits pain-sensing afferent neurons, reducing abdominal pain independent of the laxative effectstrong
  • Minimal systemic absorption — <0.1% bioavailability means very low risk of systemic side effects; acts almost entirely within the GI lumenstrong
  • Bloating improvement — significant reduction in abdominal bloating, one of the most bothersome IBS-C symptomsstrong

Dosage Protocols

RouteDosage RangeFrequencyNotes
Oral capsule (IBS-C)290 mcgOnce daily, on an empty stomach ≥30 minutes before first mealFDA-approved dose for IBS-C. Must be taken on an empty stomach to minimize diarrhea risk. Capsule should be swallowed whole, not crushed or chewed. Response is typically seen within the first week.
Oral capsule (CIC)145 mcgOnce daily, on an empty stomach ≥30 minutes before first mealLower dose approved for chronic idiopathic constipation (CIC). A 72 mcg dose is also available for patients who cannot tolerate 145 mcg. Capsule should be swallowed whole.

Medical disclaimer

Dosage information is provided for educational reference only. Always follow your prescriber's instructions and consult a qualified healthcare provider before starting any peptide protocol.

Side Effects

  • Diarrhea — the most common side effect (14–20% in IBS-C trials), usually mild-to-moderate and dose-dependent; reason for discontinuation in 4–5%common
  • Abdominal pain — mild abdominal pain or discomfort in 5–7%, typically in the first weeks and decreasing over timecommon
  • Flatulence — reported in 4–6% of patients in clinical trialscommon
  • Abdominal distension — mild bloating during initial dose titration periodcommon
  • Severe diarrhea with dehydration — rare but potentially serious, especially in pediatric patients (contraindicated in children <2 years due to deaths in neonatal mice)serious

Frequently Asked Questions

How does linaclotide differ from other IBS-C and constipation treatments?
Linaclotide is unique among IBS-C treatments because it addresses both constipation AND abdominal pain through distinct mechanisms — luminal fluid secretion (via CFTR activation) for constipation, and extracellular cGMP-mediated inhibition of visceral nociceptors for pain. Traditional laxatives (osmotic, stimulant) only address stool consistency/frequency but do not reduce pain. Lubiprostone (Amitiza) activates chloride channels but via a different mechanism (ClC-2). Plecanatide (Trulance) works through the same GC-C pathway but with pH-dependent binding. Linaclotide was the first GC-C agonist approved and has the most extensive long-term safety data.
Why is linaclotide contraindicated in children under 6?
In nonclinical studies, oral linaclotide caused deaths in neonatal mice (1–2 weeks old) due to severe diarrhea and dehydration. Juvenile mice (3+ weeks old) did not die at the same doses. Based on the immaturity of GI fluid regulation in very young animals, the FDA contraindicated linaclotide in children <2 years old and issued a warning to avoid use in children 2–17 years old. The pediatric GI tract has higher GC-C receptor density and immature compensatory mechanisms, increasing the risk of severe secretory diarrhea and life-threatening dehydration.
Why must linaclotide be taken on an empty stomach?
Taking linaclotide on an empty stomach (at least 30 minutes before the first meal of the day) is recommended because food increases the likelihood of loose stools and diarrhea. When taken with food, the peptide interacts with a food-stimulated GI environment that may enhance its secretory effect beyond the desired level. The empty-stomach dosing also provides more consistent drug exposure and efficacy. In clinical trials, patients who took linaclotide on an empty stomach had significantly lower rates of diarrhea compared to those who took it with meals.
Can linaclotide help with opioid-induced constipation?
Linaclotide is not FDA-approved for opioid-induced constipation (OIC), which has a different mechanism than IBS-C or CIC. OIC is caused by mu-opioid receptor activation on enteric neurons, reducing motility and secretion. While linaclotide can stimulate intestinal fluid secretion regardless of the constipation cause, the preferred treatments for OIC are peripherally-acting mu-opioid receptor antagonists (PAMORAs) like naloxegol, methylnaltrexone, and naldemedine, which directly reverse the opioid effect on the gut without affecting central analgesia.

References

  1. 1
    Linaclotide for irritable bowel syndrome with constipation: two randomized, double-blind, placebo-controlled phase 3 trials(2012)PubMed ↗
  2. 2
    Linaclotide for chronic idiopathic constipation: a placebo-controlled study with long-term safety data(2013)PubMed ↗
  3. 3
    Guanylate cyclase-C agonists: emerging gastrointestinal therapies and actions beyond the gut(2016)PubMed ↗

Latest Research

Last updated: 2026-02-19