# Linaclotide

Approved gut-only GC-C agonist pill for IBS-C and constipation; works for many, often too well.

- Page: https://peprank.xyz/peptides/linaclotide
- Category: Gut (Research peptide)
- Also known as: Linzess; Constella; GC-C agonist
- Routes: Oral
- Safety tier: Strict: Avoid · Balanced: Caution · Evidence only: Caution
- Risk axes (0 none to 3 severe): Seen harm 2, Mechanism 2, Data gap 0, Silent harm 0, Product 0
- Positive: 45% of 25 graded reports glowing or positive, shrunk toward the 49% all-report average by 8 reports' weight
- Rank: #44 of 61 research peptides
- Graded reports: 25 (Glowing 3, Positive 8, Mixed 3, Nothing 3, Negative 6, Bad reaction 2)
- Evidence: Approved drug — FDA-approved 2012 (IBS-C, chronic idiopathic constipation; later paediatric functional constipation and IBS-C), EU-approved as Constella for IBS-C; phase 3 RCTs in over 4,000 adults
- Access: Approved drug
- Onset: Bowel effect often within 1-4 hours of a dose (some need a few days); pain and bloating improve over 1-12 weeks
- Lasts: About a day per dose; taken once daily, and symptoms return within days of stopping
- Cost per month: ≈ €450 (researchers' estimate)
- Updated: 2026-10-30

**Why Avoid under the strict bar:** The label warns of severe diarrhoea (2% in trials), and post-marketing reports describe dehydration with fainting, low blood pressure and low potassium or sodium that needed IV fluids or hospital, plus rare anaphylaxis and angioedema. The harm is obvious at once and stops when the drug does, so under a doctor it is a reasonable IBS-C treatment, but it is a real route to serious harm and does not belong on a clean wellness list.

## What users report

Sharply split, and Reddit skews towards problems. 11 of 25 reports are favourable, several from people on it for 8-10+ years who call it the only thing that ever worked, despite daily morning diarrhoea. The commonest complaint is that it works too well: hours of urgent watery stools, accidents at work or in sleep, a whole morning planned around the toilet, worst in the first weeks and at a 290 mcg starting dose. Two describe dehydration or hives. A fair number find it stops working after weeks to months, or never works in severe slow-transit, endometriosis or EDS bowels. Felt nothing: 3 of 25 reports (12%) felt nothing even at 290 mcg; more found it faded after weeks or months.

**Effects:** more frequent, softer bowel movements, often within hours; less IBS-C abdominal pain and bloating over weeks; relief where fibre and laxatives failed

**Downsides:** diarrhoea (20% at 290 mcg vs 3% placebo), often urgent, mostly in the first 2 weeks; morning tied to the toilet; must dose 30+ min before the first meal; abdominal pain, gas and bloating in some; effect can fade over months or be erratic day to day; cost without insurance

**Risks:** Severe diarrhoea and dehydration (2% severe in trials); post-marketing reports of fainting, low blood pressure and low potassium or sodium needing IV fluids or hospital; Boxed warning: contraindicated under 2 years of age (neonatal mice died of dehydration); Contraindicated with known or suspected mechanical bowel obstruction; Rare hypersensitivity: anaphylaxis, angioedema, hives (post-marketing)

**Caveat:** The trial gains over placebo are modest (about 1 in 5 extra responders), and a sizeable minority stop for diarrhoea or find the effect fades. Linaclotide stays in the gut and has no known slow or hidden harm; it does not work on mechanical blockage or most severe slow-transit colons.

**Typical use:** IBS-C 290 mcg once daily; chronic constipation 145 mcg (or 72 mcg); children 72-145 mcg. Take on an empty stomach at least 30 minutes before the first meal; users split capsules or dose every other day to tame diarrhoea.

**Getting it:** Prescription drug: Linzess in the US (AbbVie/Ironwood), Constella in the EU and Canada. Bought from a pharmacy and minimally absorbed, so product quality is not the issue; insurers often make patients try it before Trulance or Ibsrela.

**Stacked with:** Polyethylene glycol (Miralax) (Taken alongside by many long-term users for whom linaclotide alone is not enough, even at 290 mcg.); Prucalopride (Motegrity) (The usual add-on or next step for slow transit when linaclotide fails or fades.); Senna or bisacodyl (A stimulant laxative alongside, for example one ten-year user on 290 mcg plus five senna tablets each evening. Plecanatide (Trulance) is the same-class alternative people switch to, not something to combine.)

## Risk profile

- **Seen harm 2/3:** The label carries an adult warning for severe diarrhoea (2% at 145-290 mcg in trials vs under 1% on placebo). Post-marketing reports describe severe diarrhoea with dizziness, fainting, low blood pressure and low potassium or sodium that needed hospital or IV fluids, plus anaphylaxis and angioedema. Two of 25 Reddit reports describe dehydration or hives. The harm depends on dose and is avoided by stopping and rehydrating; the scale gives no discount for that.
- **Mechanism 2/3:** GC-C activation pumps chloride, bicarbonate and water into the gut. At use doses this is the intended effect, but it can tip into volume and electrolyte loss with low blood pressure, as seen post-marketing; in neonatal mice one adult-equivalent dose killed by dehydration. It acts only in the gut, so there is no systemic hormone, growth or immune pathway.
- **Data gap 0/3:** FDA-approved since 2012 and EU-approved as Constella, with phase 3 RCTs in over 4,000 adults, open-label safety studies of up to 18 months in more than 3,000, paediatric trials, and over a decade of post-marketing use.
- **Silent harm 0/3:** The harm is diarrhoea and dehydration, mostly in the first two weeks and within hours of a dose; it is obvious at once and resolves on stopping. The drug is minimally absorbed and has no known delayed or silent harm.
- **Product 0/3:** A regulated oral prescription capsule from a pharmacy (Linzess, Constella); there is no grey-market channel.
- **Never if:** Children under 2 years (boxed warning, risk of fatal dehydration); Known or suspected mechanical bowel obstruction; Previous anaphylaxis or angioedema on linaclotide

## Top reports

- Glowing, gut, 145 mcg: “Linzess is the only thing that keeps me going everyday. 145mcg” — [r/ibs](https://www.reddit.com/r/ibs/comments/zyto4t/linzess_hell_in_a_pill/j293h8h/)
- Glowing, gut: “So I took a colonoscopy prep drink, waited a few days to start Linzess consistently since I've only used it as needed in the past, and guys, I feel AMAZING 😭🙏🏼” — [r/ibs](https://www.reddit.com/r/ibs/comments/1m3qaps/linzess_has_saved_me/)
- Glowing, gut, lowest dose (72 mcg): “Yes! I don’t have crazy abdominal pain like I use to. If I feel cramping, I know it’s temporary.” — [r/ibs](https://www.reddit.com/r/ibs/comments/1pifapn/linzess_has_changed_my_life/nxjx85n/)
- Positive, gut: “Constipation- basically gone, BM every day or close to” — [r/ibs](https://www.reddit.com/r/ibs/comments/1scn25s/been_on_linzess_for_a_week_now_heres_my_thoughts/)
- Positive, gut: “I agree, it’s not my favorite med but there’s a reason I take it. Any time I’ve stopped, I’ve regretted it greatly!” — [r/ibs](https://www.reddit.com/r/ibs/comments/1pifapn/linzess_has_changed_my_life/nt5ll1m/)

## Studies

- [Chey et al., Linaclotide for IBS-C: a 26-week, randomized, double-blind, placebo-controlled trial (Am J Gastroenterol 2012)](https://pubmed.ncbi.nlm.nih.gov/22986437/) (rct, n=804, 2012): 290 mcg daily: 33.7% met the FDA responder end point (pain plus bowel movements) vs 13.9% on placebo (NNT 5); diarrhoea led 4.5% to stop vs 0.2% on placebo.
- [Lembo et al., Two randomized trials of linaclotide for chronic constipation (N Engl J Med 2011)](https://pubmed.ncbi.nlm.nih.gov/21830967/) (rct, n=1276, 2011): Over 12 weeks, 16-21% on 145 or 290 mcg reached three or more complete spontaneous bowel movements a week vs 3-6% on placebo; diarrhoea made 4.2% stop.
- [Black et al., Efficacy of secretagogues in IBS-C: systematic review and network meta-analysis (Gastroenterology 2018)](https://pubmed.ncbi.nlm.nih.gov/30144426/) (meta-analysis, n=8462, 2018): Across 15 RCTs, linaclotide 290 mcg ranked first for the FDA end point, abdominal pain and bowel movements, though efficacy was similar among the secretagogues; diarrhoea was more common than with placebo.
- [Shah et al., Efficacy and tolerability of guanylate cyclase-C agonists for IBS-C and CIC: systematic review and meta-analysis (Am J Gastroenterol 2018)](https://doi.org/10.1038/ajg.2017.495) (meta-analysis, n=10369, 2018): Pooling 8 linaclotide and 7 plecanatide trials, efficacy, diarrhoea and diarrhoea dropouts did not differ significantly between the two drugs; the trials defined diarrhoea differently, which inflates linaclotide's label rate.
- [Castro et al., Linaclotide inhibits colonic nociceptors and relieves abdominal pain via GC-C and extracellular cGMP (Gastroenterology 2013)](https://doi.org/10.1053/j.gastro.2013.08.017) (animal, 2013): In mice, linaclotide-driven cGMP released from gut lining quietened colonic pain nerves, most strongly in chronic visceral hypersensitivity, which would explain the pain relief beyond laxation.

## Sources

- [LINZESS (linaclotide) full prescribing information (revised 10/2026)](https://www.rxabbvie.com/pdf/linzess_pi.pdf)
- [EMA EPAR: Constella](https://www.ema.europa.eu/en/medicines/human/EPAR/constella)
- [Superpower peptide guide: Linaclotide](https://superpower.com/guides/peptides/linaclotide)