FDA approves Linzess (linaclotide) for paediatric irritable bowel syndrome with constipation in ages 6–17

FDA has approved a paediatric indication for Linzess (linaclotide), expanding its use to patients aged 6 to 17 years with irritable bowel syndrome with constipation (IBS-C). Linaclotide is a guanylate cyclase-C (GC-C) agonist that acts luminally in the gut to increase intestinal fluid secretion and transit. It was already approved for adults with IBS-C and chronic idiopathic constipation (CIC). The paediatric approval required dose selection studies (CONFIDENCE trial) and was mandated under the Pediatric Research Equity Act (PREA). The approved paediatric dose for IBS-C ages 6–17 is 72 mcg once daily before breakfast. Linzess remains contraindicated in patients under 6 years due to neonatal mouse mortality observed at high doses. See FDA Pediatric Drug Approvals ↗.

Linaclotide is a 14-amino acid peptide that acts as a potent agonist at guanylate cyclase-C (GC-C) receptors on intestinal epithelial cells. It is minimally absorbed systemically — acting locally in the gut lumen. Activation of GC-C increases intracellular cGMP, which activates CFTR chloride channels and reduces NHE3 sodium/hydrogen exchange, resulting in net luminal fluid secretion that softens stool and accelerates transit. Additionally, elevated cGMP reduces visceral afferent pain signalling via inhibition of submucosal sensory neurons — the mechanism underlying the abdominal pain reduction seen in IBS-C trials. For a broader discussion of paediatric pharmacology differences see paediatric pharmacology guide.

The CONFIDENCE trial was a Phase 3, double-blind, randomised, placebo-controlled study in patients aged 6–17 with IBS-C. The primary endpoint was the proportion of paediatric IBS-C patients with ≥30% improvement in abdominal pain AND ≥1 complete spontaneous bowel movement increase per week — a composite responder criterion aligning with adult FDA IBS-C endpoint definitions. The most common adverse effect was diarrhoea (~13% linaclotide vs 3% placebo), consistent with its mechanism. The trial required separate dose-finding studies for the 6–11 and 12–17 age groups to account for body weight-based exposure differences, as paediatric PK data (weight-normalised GI surface area and transit time) differ from adults. See paediatric pharmacology and how to read a clinical trial.

Linzess should be taken on an empty stomach at least 30 minutes before the first meal of the day. Dispensing in child-resistant containers is critical — the FDA Boxed Warning cautions that paediatric deaths (in juvenile mice) were dose-related and due to severe dehydration; this contraindication in patients under 6 is absolute. For children aged 6–17, the risk-benefit favours use when IBS-C symptoms are inadequately controlled by dietary modification and osmotic laxatives. Pharmacists should counsel carers about safe storage, the absolute contraindication in children under 6, and signs of excessive diarrhoea or dehydration. Related: drug safety monitoring guide.