toxylact: a06ax04 linaclotide

The first professional lActological database in the word


Linaclotide (A06AX04) is a minimally absorbed guanylate cyclase‑C agonist used for IBS‑C and chronic idiopathic constipation, and current data indicate that it is not detectable in human breast milk at therapeutic doses, making it acceptable for use in nursing mothers without special precautions.atcddd.fhi+7

Pharmacotherapeutic group and mechanism

Linaclotide is classified in ATC subgroup A06AX “Other drugs for constipation” with specific code A06AX04.atcddd.fhi+4
It is a 14‑amino‑acid peptide that acts as a guanylate cyclase‑C (GC‑C) receptor agonist on the luminal surface of intestinal epithelial cells, increasing cyclic GMP, stimulating chloride and bicarbonate secretion via CFTR, enhancing intestinal fluid and accelerating transit; it also exerts visceral analgesic effects that improve abdominal pain in IBS‑C.pubmed.ncbi.nlm.nih+4

Indications, dosage and administration

Linaclotide is indicated for the treatment of irritable bowel syndrome with constipation (IBS‑C) in adults, and in many regions also for chronic idiopathic constipation (CIC); in the US it is additionally approved for functional constipation in pediatric patients 6–17 years of age.pubmed.ncbi.nlm.nih+2
The WHO ATC/DDD Index lists linaclotide with a defined daily dose of 0.29 mg (290 micrograms) oral, based on IBS‑C treatment.atcddd.fhi+1

Typical adult dosing is:

  • IBS‑C: 290 micrograms orally once daily, taken at least 30 minutes before a meal.pubmed.ncbi.nlm.nih+2

  • CIC: 145 micrograms orally once daily; a 72 microgram dose is also available in some markets for CIC.pubmed.ncbi.nlm.nih+2

Linaclotide capsules are swallowed whole and not crushed or chewed; treatment should be reassessed if no response is observed within several weeks.pubmed.ncbi.nlm.nih+2

General toxicological profile

Because linaclotide acts locally in the intestinal lumen and is minimally absorbed, systemic adverse effects are rare; the main treatment‑emergent adverse event is diarrhea, which can lead to discontinuation in up to about 5% of patients.pubmed.ncbi.nlm.nih
Other common gastrointestinal adverse reactions include abdominal pain, distension, flatulence and, less frequently, fecal incontinence; dehydration and electrolyte disturbances can occur secondary to severe diarrhea, and therapy should be interrupted or reduced if significant diarrhea develops.pubmed.ncbi.nlm.nih+2

Systemic exposure to linaclotide and its active metabolite MM‑419447 is negligible at recommended doses, with plasma concentrations generally below quantitation limits; this underlies the favourable systemic safety profile observed in clinical trials. Linaclotide is contraindicated in patients with known or suspected mechanical gastrointestinal obstruction, and caution is advised in pediatric populations outside approved age ranges because of the risk of severe dehydration.pubmed.ncbi.nlm.nih+4

Lactation‑toxicology considerations

Linaclotide is minimally absorbed from the maternal gastrointestinal tract, and pharmacokinetic studies show that the drug and its active metabolite are not measurable in human breast milk following administration of doses up to 290 micrograms daily.academic.oup+2
In a dedicated milk pharmacokinetic study, breast milk concentrations of linaclotide and MM‑419447 were below the quantitation limits (<0.25 ng/mL and <1.0 ng/mL, respectively) at all sampling time points for all participants receiving 72, 145 or 290 micrograms once daily, providing no evidence that breastfeeding infants receive linaclotide or its metabolite through breast milk.academic.oup+1

On this basis, lactation references conclude that linaclotide appears acceptable in nursing mothers and that no special precautions (such as routine infant monitoring beyond standard clinical care) are required. The prescribing information notes that it is not known whether linaclotide is excreted in human milk but, given the minimal systemic absorption and non‑measurable milk levels, the risk of clinically relevant exposure to breastfed infants is considered very low.drugs+3

General guidance on laxatives during breastfeeding supports this position, stating that any laxative can usually be used in breastfeeding, as most are not absorbed or only minimally absorbed, leading to low or negligible levels in breast milk; safer, more established alternatives are often recommended first, but linaclotide is a reasonable option when indicated.sps+2

Clinical use in breastfeeding women

For breastfeeding women with IBS‑C or chronic idiopathic constipation, first‑line management should still emphasize dietary and lifestyle measures and laxatives with extensive lactation safety data (bulk‑forming and osmotic agents).sps+1
When these measures fail and linaclotide is clinically indicated—especially in moderate to severe IBS‑C with pain and bloating—available evidence supports its use at standard doses without interruption of breastfeeding, given the lack of detectable drug or metabolite in milk and negligible systemic absorption in the mother.academic.oup+4

Clinicians should counsel nursing mothers on potential maternal side effects, primarily diarrhea and abdominal symptoms, and advise them to report any changes in infant health, although specific adverse effects in breastfed infants are not anticipated based on current data. Treatment decisions should weigh the maternal benefits of IBS‑C or CIC control against the very low theoretical infant risk, typically favouring continued breastfeeding alongside linaclotide therapy when symptoms significantly impair quality of life.pubmed.ncbi.nlm.nih+2


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