Linaclotide
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FDA-approved guanylate cyclase-C (GC-C) agonist peptide for IBS-C and chronic idiopathic constipation; dual action on secretion and visceral pain.
Quick Facts
| Property | Value |
|---|---|
| Also Known As | Linzess (US), Constella (EU), MD-1100 |
| Category | GI / Gastrointestinal peptide |
| Sequence | 14 amino acids with 3 disulfide bonds (Cys1-Cys6, Cys2-Cys10, Cys5-Cys13) |
| Molecular Weight | ~1527 Da |
| Molecular Formula | C₅₉H₁₀₄N₁₈O₂₈S₆ |
| PubChem CID | 16137698 |
| Administration | Oral (capsule) |
| Typical Dose Range | 72 mcg (CIC), 290 mcg (IBS-C) once daily |
| Half-Life | Negligible systemic exposure; acts locally in GI lumen. Active metabolite (MM-419447) also acts locally |
| Storage | Room temperature (20-25 C); keep in original container with desiccant |
| FDA Status | FDA Approved (2012) — IBS-C and chronic idiopathic constipation (Linzess, Allergan/AbbVie) |
| WADA Status | Not listed |
Mechanism of Action
Linaclotide is a 14-amino acid synthetic peptide structurally related to the endogenous GI peptides guanylin and uroguanylin. It functions as a potent and selective agonist of guanylate cyclase-C (GC-C), a transmembrane receptor expressed on the luminal surface of intestinal epithelial cells. Upon binding to GC-C, linaclotide stimulates intracellular production of cyclic guanosine monophosphate (cGMP) (PMID-23958540).
Intracellular cGMP activates the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel via cGMP-dependent protein kinase II (PKGII). This triggers chloride and bicarbonate secretion into the intestinal lumen, followed by passive water secretion, resulting in accelerated intestinal transit and softer stool consistency. This is the pro-secretory/pro-motility arm of linaclotide's dual mechanism.
The second arm involves visceral analgesia. cGMP produced inside epithelial cells is actively exported to the extracellular space via multidrug resistance protein 4 (MRP4). Extracellular cGMP then acts on submucosal nociceptive afferent neurons, inhibiting their firing and reducing visceral pain signaling to the spinal cord. Critically, this analgesic effect is enhanced in states of visceral hypersensitivity, making linaclotide particularly effective in the pathological pain of IBS-C (PMID-23958540).
Linaclotide has negligible oral bioavailability (<0.1%) and acts entirely within the GI lumen. It is proteolytically degraded in the intestine to its active metabolite MM-419447, which retains GC-C agonist activity. This local mechanism minimizes systemic side effects.
Key Research Areas
- IBS-C treatment — Multiple Phase III RCTs demonstrated significant improvement in both abdominal pain and bowel function vs placebo (PMID-29380823)
- Chronic idiopathic constipation — FDA-approved for CIC at 72 mcg/day with consistent efficacy across meta-analyses (PMID-34215016)
- Visceral pain modulation — Unique dual mechanism: secretory + analgesic via extracellular cGMP acting on nociceptors (PMID-23958540)
- GC-C signaling — Platform molecule for understanding guanylate cyclase-C biology and its role in GI physiology
- Colorectal cancer chemoprevention — Emerging research on GC-C/cGMP pathway in intestinal epithelial homeostasis and tumor suppression
Evidence Level Summary
| Evidence Type | Count | Notes |
|---|---|---|
| Human RCTs | Multiple | Phase II and III trials for IBS-C and CIC |
| Systematic reviews | 2+ | Meta-analyses confirming class efficacy |
| Human observational | Several | Post-marketing surveillance data |
| Animal in vivo | Several | Mechanistic studies in rodent pain models |
| In vitro | Several | GC-C signaling pathway characterization |
Clinical Applications
- Gut Health — Primary indication: IBS-C and CIC management
- Gastric Ulcers — Related GI condition (not primary indication)
Protocols Using This Peptide
- Gut Healing Protocol — Reference peptide for GI motility comparison
Ageless Peps Products
Linaclotide is an FDA-approved prescription medication (Linzess) and is NOT sold by Ageless Peps. It is included in this vault for educational reference and to provide context for the GC-C signaling pathway relevant to GI peptide therapy.
Dosing Reference
FDA-Approved Dosing
| Route | Dose | Frequency | Duration | Source |
|---|---|---|---|---|
| Oral | 290 mcg | Once daily, 30 min before first meal | Chronic (ongoing) | FDA label (IBS-C) |
| Oral | 72 mcg | Once daily, 30 min before first meal | Chronic (ongoing) | FDA label (CIC) |
Cycling
Not applicable — linaclotide is used as chronic daily therapy without cycling. Onset of constipation relief within 1 week; abdominal pain improvement may take 2-4 weeks.
Contraindications & Safety
- Contraindications: Known mechanical GI obstruction; pediatric patients <2 years (boxed warning — fatal dehydration in neonatal mice)
- Common side effects: Diarrhea (most common, ~20% in IBS-C trials; dose-related), abdominal pain, flatulence, abdominal distension
- Drug interactions: No significant systemic drug interactions due to negligible absorption
- Pregnancy/nursing: Category C; unknown if excreted in breast milk (minimal systemic absorption suggests low risk)
- Special populations: Avoid in children <6 years; use with caution in ages 6-17
Synergistic Combinations
As a prescription medication, linaclotide is typically used as monotherapy. In functional medicine contexts, it may be used alongside:
- BPC-157 — BPC-157 for mucosal healing + linaclotide for motility/pain
- KPV — Anti-inflammatory complement for IBS patients
Related Research
| PMID | Title | Year | Study Type |
|---|---|---|---|
| 29380823 | GC-C Agonists IBS-C/CIC Systematic Review & Meta-Analysis | 2018 | Systematic Review / Meta-Analysis |
| 23958540 | Linaclotide Inhibits Colonic Nociceptors via GC-C and cGMP | 2013 | Animal in vivo / In vitro |
| 34215016 | Linaclotide for CC and IBS-C: Meta-Analysis | 2021 | Meta-Analysis |
References
- PMID-29380823 — Shah et al., GC-C agonists meta-analysis, Am J Gastroenterol 2018
- PMID-23958540 — Castro et al., Nociceptor inhibition, Gastroenterology 2013
- PMID-34215016 — Yang et al., Linaclotide meta-analysis, Expert Rev Gastroenterol Hepatol 2021
Related
FDA Disclaimer: Linaclotide (Linzess) is an FDA-approved prescription medication. This vault entry is for educational and research reference only. It does not constitute medical advice. Consult a qualified healthcare provider for prescribing information.
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