Linaclotide

Areas of active research — not promised effects

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Linzess (linaclotide) is a fully FDA-approved prescription medication for IBS-C and CIC in adults and select pediatric populations. It is commercially available by prescription through licensed pharmacies. Generic formulations (linaclotide 145 mcg and 290 mcg capsules) have also received FDA approval.

Transparent blend · bci-1.0 · never paid-placement

Primary name

Linaclotide

Origin

Synthetic 14-amino-acid peptide structurally related to the endogenous heat-stable enterotoxin peptides (uroguanylin and guanylin); developed by Ironwood Pharmaceuticals and AstraZeneca

Registry IDs

PubChem CID

16158208

CAS

851199-59-2

InChIKey

KXGCNMMJRFDFNR-WDRJZQOASA-N

DrugBank

DB08890

ChEMBL

CHEMBL3301675

Molecular formula

C59H79N15O21S6

Molar mass

1526.8 g/mol

Monoisotopic

1525.3899216 Da

InChIKey

KXGCNMMJRFDFNR-WDRJZQOASA-N

Appearance

White to off-white lyophilized powder; commercially available as oral capsules (72 mcg, 145 mcg, 290 mcg)

Solubility

Soluble in water; the cyclic disulfide-bonded structure confers gastric acid sta…

Sequence not available in current seed.

Stability: Stable in simulated gastric fluid (pH 1) for at least 3 hours; completely degraded within 30 minutes in intestinal (jejunal) fluid due to endopeptidase activity

Vial sizes

null mg

Purity grades

pharmaceutical (NDA/ANDA grade) / research grade

Salt forms

Free base (primary)

• GHS hazard class on file
• PPE & spill response
• Disposal guidance
• Not-for-human-consumption posture

How much research exists, and of what maturity — never a verdict on whether it works.

Mechanism of action

• Linaclotide binds selectively to guanylate cyclase-C receptors expressed on the luminal surface of intestinal epithelial cells, stimulating intracellular and extracellular production of cyclic GMP (cGMP)
• Elevated intracellular cGMP activates the cystic fibrosis transmembrane conductance regulator (CFTR), promoting chloride and bicarbonate secretion into the intestinal lumen while inhibiting sodium absorption, thereby increasing luminal fluid content and accelerating intestinal transit
• Extracellular cGMP released into the lamina propria additionally attenuates activity of pain-sensing afferent neurons, contributing to visceral analgesic effects observed in IBS-C
• Because GC-C is expressed primarily on intestinal epithelium and oral bioavailability is negligibly low (<0.1%), pharmacological activity is confined to the gastrointestinal tract with no measurable systemic exposure at therapeutic doses

Pharmacokinetics (ADME)

Half-life

Plasma half-life not quantifiable; degraded in the intestinal lumen with an in vitro jejunal first-order half-life of approximately 30 minutes

Clearance

Locally metabolized in the small intestine; principal active metabolite MM-419447 (des-Tyr linaclotide) formed by loss of C-terminal tyrosine; minimal systemic absorption

PK–PD note: Even at supratherapeutic doses (single 3000 mcg or repeated 1000 mcg), plasma concentrations of linaclotide and its active metabolite remain below the limit of quantification; PK/PD relationship is dr…

Reading the evidence

• Evidence quality and gaps vary by application — see the cited grades above.
• Indexed-article counts span all evidence tiers, not only completed human trials.
• No first-party human-dosing, efficacy, or benefit claims are made here.

Key reviews & evidence-gap sources

• Pharmacokinetics, pharmacodynamics, clinical efficacy, safety and tolerability of linaclotide (review, lit to Jan 2011)
• Linaclotide: a new drug for chronic constipation and IBS-C (systematic review)
• Effects of linaclotide in IBS-C or CC: a meta-analysis
• Combined linaclotide and PEG for colonoscopy prep: network meta-analysis of 14 RCTs

5 registered trials — 0 currently recruiting.

Phase 3
NCT04166058
Long-term Safety of Linaclotide in Pediatric Participants With FC or IBS-C

COMPLETED

Phase 1
NCT02220348
A Lactation Study in Women Who Are Breastfeeding or Pumping and Are Receiving Linaclotide Therapeutically

COMPLETED

Phase 2
NCT00402337
Dose-range-finding, Phase 2 Trial of Oral Linaclotide Acetate Administered to Patients With Chronic Constipation

COMPLETED

Phase 3
NCT00948818
Trial of Linaclotide Administered to Patients With Irritable Bowel Syndrome With Constipation

COMPLETED

Phase 3
NCT04804267
Evaluation of Clinical Equivalence Between Two Linaclotide Products in the Treatment of Chronic Idiopathic Constipation

UNKNOWN

Summary (literature)

Per the FDA-approved prescribing information, linaclotide carries a boxed warning: it is contraindicated in pediatric patients under 2 years of age based on neonatal animal studies showing fatal dehydration, and should be avoided in patients aged 2 to 6 years. The most common adv…

WADA status

Not specifically listed on the 2026 WADA Prohibited List; linaclotide is an approved gastrointestinal therapeutic with no identified performance-enhancing mecha…

Animal & human figures are kept visibly separate so studied animal doses are never misread as human guidance.

Sorted A–Z by vendor — never by price

DrugPrice reports brand Linzess +6.4% YoY on Medicare Part D claims, but generic linaclotide is now available (typically 80-95% cheaper than brand), exerting downward pressure on net pricing. Research-chem reagent pricing appears stable.

Researched storefront prices, bucketed

p25 $41.38 · median $59.17 · p75 $104.87 · 7 researched vendors

Legit, COA-backed band: $9.99–$104.87/mg.

Value rule: don't just buy the cheapest — a price under $3/mg is a red flag. Pair price with COA and independent-test grade.

Estimated cost of research (10 mg)

Vial (best researched price)

$100

Bacteriostatic water (generic estimate)

$6

Syringes / supplies (generic estimate)

$12

What each test proves — general guidance, plus this compound's researched purity data

Purity on the current market (researched)

≥95% (research-grade linaclotide per supplier specification; RP-HPLC purification to >95% reported in medicinal chemistry literature)

Independent labs cited for this compound

One FDA recall found for Linzess (linaclotide): Class II recall D-0417-2021 (March 2021) for CGMP deviations due to intermittent temperature excursion during storage, affecting Lot W04411 (72 mcg capsules, 1,529 bottles). Recall status: Terminated (June 17, 2024). No counterfeit or criminal events specific to linaclotide were identified in available sources.

Buyer red-flag checklist

• Temperature sensitivity: Class II recall due to temperature excursion during storage indicates linaclotide potency may be affected by improper storage conditions.
• Boxed warning: Linzess is contraindicated in patients less than 2 years of age; neonatal mouse deaths due to dehydration observed preclinically.
• FDA Untitled Letter (Sept 2025) regarding promotional DTC advertising for Linzess.
• No counterfeit-specific events found for linaclotide, but unapproved imports of linaclotide could be subject to FDA Import Alert 66-41 (DWPE of unapproved new drugs).

GMP vs research-grade: the chemistry (SPPS + HPLC + MS) is identical — the difference is the quality system.

Underdosing / mislabeling: No independent lab test data (Janoshik, MZ Biolabs, Finnrick, or similar) specific to linaclotide underdosing or mislabeling were identified in available sources. Linaclotide is an FDA-approved prescription drug (Linzess) distributed through regulated pharmacy channels, which limits the availability of grey-market testing data compared to non-approved research peptides.

• Import Alert 66-41: Detention Without Physical Examination of Unapproved New Drugs Promoted in the U.S. Applies to unapproved new drug products imported without FDA-approved applications. Linaclotide is an FDA-approved drug (NDA 202811); non-approved linaclotide imports marketed with drug claims could fall under this alert. Linaclotide is not specifically named on the Red List in the alert text retrieved.66-41
• An RUO label is not an import exemption — CBP judges actual intended use.
• Lyophilized powder is ambient-stable in transit; temperature control needed for > 7-day transit.
• US-warehouse vendors dodge import scrutiny — they cost more but ship more reliably.

Every item dated & sourced

No granted patents identified in current seed. Composition-of-matter coverage is limited given the peptide's synthetic origin.

• IACUC / IRB research context
• RUO buyer responsibilities & documentation
• Veterinary / alternative-use where lawful
• Jurisdiction-aware "who may lawfully obtain"

What people discuss

Reported concerns — discussion, not established effects

Reading caveats

• Self-selected patient review platforms skew toward negative experiences
• Cost/insurance complaints overrepresented in US-centric threads
• Brand name (Linzess) dominates discourse over generic linaclotide

Manually researched from reddit, youtube— theme weights are research estimates, not live counts; aggregated & de-identified. No individual posts, quotes, or usernames are ever shown.

Relative research / market volume — populated once the activity stream is wired

Inline tooltips for lyophilized, RUO, EU/mg, SPPS, 503A and more.

Toggle plain-language ↔ scientific in the header.

• How to read a COA
• Free base vs acetate
• Understanding evidence grades

FDA-approved synthetic peptide agonist of guanylate cyclase-C that treats IBS-C and chronic idiopathic constipation in adults and eligible pediatric patients. Approximately 491 articles are indexed (literature last scanned 2026-05-29). US regulatory status: FDA-approved prescription drug. Research use only.

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