Linaclotide
Approved for IBS with constipation and chronic constipation.
A peptide capsule that works inside the gut and is barely absorbed. It draws fluid into the bowel and dulls pain nerves there. It shows that an oral peptide can be an ordinary, approved medicine. A made by AbbVie and Ironwood, also called Linzess and Constella.
What the evidence shows
Side effects and risks
Who should avoid it: Children under 2, and anyone with a bowel blockage.
How it works
- Where it acts
- Guanylate cyclase-C receptors on the lining of the gut.
- What it changes
- More fluid released into the bowel, and calmer pain nerves in the gut wall.
- What people notice
- Softer, more frequent stools within days. Diarrhoea is the main side effect.
How it is taken
One capsule a day on an empty stomach, at least 30 minutes before a meal, at about the same time each day. The adult dose is 290 micrograms for IBS and 145 micrograms for constipation.
Getting it in the United States
The legal route for Linaclotide
Get a prescription from a licensed clinician. Fill it at a licensed pharmacy or through the maker's own direct service.
Prescription, brand only
Sold only as a brand with no generic as of late 2025. A discount-card listing put 30 capsules near 600 dollars. The maker coupon may not work with Medicare. Some plans need prior authorization.
Source: Healthline, 2025-09
Medicare Part D from 2027
Medicare negotiated a price of 136 dollars for a 30-day supply, starting 2027-01. Until then, what a patient pays depends on plan tier. The cut applies to Medicare only.
Source: 340B Report, 2025-11
Prescription for children 2 and up
Since May 2026 the US label covers functional constipation in children aged 2 and older. Children under 2 must never take it because young mice died of dehydration in testing.
Source: FDA label via Drugs.com, 2026-05
Routes people use for any peptide in the United States
Telehealth prescribing
Online clinics prescribe after a questionnaire, sometimes with no live doctor visit, and mail the drug. FDA moved in February 2026 to restrict mass-marketed compounded copies and claims that they are generic equivalents.
Risk: Thin medical screening. Compounded versions are not reviewed by FDA for quality.
Covers: Approved GLP-1 drugs, compounded semaglutide and tirzepatide
Source: GZERO Media, Apr 2026
Clinical trial enrolment
The only lawful way to get an unapproved peptide drug with medical monitoring. ClinicalTrials.gov lists eligibility, sites and phone numbers. Researchers note recruitment is hard when people can buy the drug on the gray market instead of risking placebo.
Risk: Possible placebo assignment, strict eligibility and travel to a study site.
Covers: Investigational peptide drugs still in development
Source: NIH, finding a clinical trial
Routes people use for any peptide in the United States
Compounding pharmacy with prescription
A clinician prescribes and a pharmacy compounds. Twelve peptides left the FDA do-not-compound category in April 2026 and a panel backed six in July, but they are not yet formally eligible. Pharmaceutical-grade ingredient is scarce.
Risk: Legal status is unsettled until FDA rulemaking ends. Pharmacies may use research-grade ingredient.
Covers: BPC-157, TB-500, KPV, MOTS-c, Semax, Epitalon and similar
Source: Frier Levitt, Apr 2026
Med spas and weight-loss clinics
Very common. Secret shoppers called 75 clinics and med spas in two states after shortages ended. 92 percent offered compounded semaglutide and 87 percent tirzepatide, often mixed with B vitamins to look custom.
Risk: Four of 23 suppliers lacked sterile compounding licenses and four had disciplinary records.
Covers: Compounded semaglutide and tirzepatide
Source: American Med Spa Association on JAMA Health Forum study, Jul 2026
Concierge and longevity doctors
Cash-pay physicians build peptide plans for wealthy clients. Reporting from San Francisco says some source from overseas channels, domestic research-use-only sellers or the few compounding pharmacies that will supply clinicians.
Risk: A doctor's involvement does not guarantee a pharmaceutical-grade product.
Covers: BPC-157, thymosin alpha-1, Selank, Semax, CJC-1295, ipamorelin, retatrutide
Source: San Francisco Standard, Sep 2025
Cross-border purchase or import
FDA says importing drugs for personal use is illegal in most cases but it may not object to small personal quantities in limited situations. Reporting also describes people travelling to Mexico for injections.
Risk: Packages can be seized. Product origin and cold-chain handling are hard to check.
Covers: Approved prescription peptides sold abroad
Source: FDA, personal importation
Routes people use for any peptide in the United States
Research-chemical websites
Sites sell vials marked for research or not for human consumption, with no prescription. FDA says some ship direct to consumers with dosing directions, and it has sent warning letters. Retatrutide exists only through this route or trials.
Risk: Unknown identity, strength and sterility. No pharmacist or prescriber involved.
Covers: Retatrutide, semaglutide, tirzepatide, BPC-157 and most unapproved peptides
Source: FDA, unapproved GLP-1 drugs page
Direct orders from Chinese factories
Buyers message factory sales agents and pay by crypto or payment app. A minimum order of about ten vials pushes people to buy in bulk and share. A blockchain analysis found US buyers were the largest source of funds.
Risk: Many of the same vendors list fentanyl precursors. Lab reports sent by sellers cannot be verified.
Covers: GLP-1 copies, melanotan II, BPC-157, TB-500, GHK-Cu, epitalon
Source: TRM Labs, Oct 2026
Chat groups and social sellers
Dealers are found through Telegram, WhatsApp, Discord and influencer discount codes. In a May 2026 survey of 1,000 US users, 14.5 percent bought this way and three quarters asked an AI chatbot for dosing.
Risk: 45 percent of social media buyers in that survey reported an emergency or urgent care visit for a reaction.
Covers: Retatrutide and other research-use-only peptides
Source: The Ethos, May 2026
This describes what people do. It is not advice. The decision is yours.
More contextCase reports, what public figures say, videos and articles and the chemistry
Case reports
From journals, regulators and studies of users. One case proves little.
Harm reportedcase series - 3 people - 2025
Public Citizen reports at least three ischemic colitis cases in pre-approval trials and one peritonitis case in a trial participant. It says an FDA reviewer wanted a warning that the label does not carry.
Source: Boletin Farmacos, 2026-02
What experts and influencers say
Paraphrased from the linked sources.
Lists linaclotide as Do Not Use. Says about one in five users got relief and about one in five got diarrhea. Says the label omits ischemic colitis and diverticulitis. Sent comments to Medicare on its price.
Source: Worst Pills, Best Pills, 2025-10
Public Citizen Health Research GroupSourceWarns against
Told Reuters the second round of Medicare negotiated prices, which includes Linzess, would land below existing net prices. He did not comment on the drug's clinical value.
Source: Reuters via AOL, 2025-11
Sean SullivanWebsiteMixed view
Photo source: sop.washington.edu
Republished the Do Not Use advice in Spanish for Latin American readers. Recommends fibre, fluids, exercise and short-term bulk laxatives first. Notes no trial compared linaclotide with older laxatives.
Source: Boletin Farmacos, 2026-02
Salud y FarmacosSourceWarns against
Watch and read
Explainers, reporting and podcasts worth your time. Summaries are ours. No sellers.
Linaclotide: MedlinePlus Drug Information
National Library of Medicine, NIH
Patient guide to linaclotide for IBS with constipation and chronic constipation, including the warning that children under 2 should never take it.
Trusted NIH patient guide with the key safety warning
FDA approves first treatment for pediatric functional constipation
FDA
FDA announcement of Linzess approval for children 6 to 17 with functional constipation, with a boxed warning against use under age 2.
Regulator news with a clear pediatric safety warning
How DTC got things moving for Linzess
Lisa LaMotta
Business story on how Ironwood and its partner marketed Linzess directly to consumers, helping grow US sales to $626 million in 2016.
Shows how a peptide drug reached the mass market
Amino-acid sequence
Held in shape by three disulfide bridges.
Questions people ask
How does Linzess work?
Linaclotide works inside the gut and is barely absorbed. It draws fluid into the bowel and dulls pain nerves there, giving softer, more frequent stools within days.
What are the side effects of Linzess?
Diarrhea affects 16% to 20% of users and is severe in about 2%.
Can children take linaclotide?
In the US it is approved for children from age 2 with functional constipation, and a boxed warning bars it under 2 because of the risk of serious dehydration. Canada bars it under age 6, and the EU license is for adults only.
Is Linzess the same as Constella?
Yes. Both are linaclotide: Linzess in the US, Constella in the EU, UK and Canada.
How do you take Linzess?
One capsule a day on an empty stomach, at least 30 minutes before a meal, at about the same time each day.
Your notebook
Taking it? A ten-second daily check-in keeps a record of how you feel, to talk through with your clinician.
Sources
Structure: PubChem