toxylact: a06ah02 alvimopan

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Alvimopan (A06AH02) is a peripherally acting µ‑opioid receptor antagonist used short‑term to accelerate gastrointestinal recovery after bowel resection, and its use during breastfeeding requires caution because of animal milk excretion data and lack of human lactation studies.atcddd.fhi+7

Pharmacotherapeutic group and mechanism

Alvimopan belongs to ATC subgroup A06AH “Peripheral opioid receptor antagonists” with code A06AH02 and is classified as a laxative‑type agent targeting opioid‑induced bowel dysfunction.atcddd.fhi+2
It is an orally administered, peripherally selective µ‑opioid receptor antagonist that competitively blocks opioid receptors in the gastrointestinal tract, reversing opioid‑induced inhibition of motility and secretion without significantly affecting centrally mediated analgesia.pubmed.ncbi.nlm.nih+3

Indications, dosage and administration

Alvimopan is indicated to accelerate the time to upper and lower gastrointestinal recovery following partial large or small bowel resection surgery with primary anastomosis, thereby reducing the duration of postoperative ileus.drugbank+4
Typical adult dosing in the perioperative setting is 12 mg orally 30 minutes to 5 hours before surgery, followed by 12 mg twice daily beginning the day after surgery, continued for up to 7 days or until hospital discharge; use is restricted to hospitalized patients due to long‑term cardiovascular safety concerns observed in earlier studies.mayoclinic+3
The WHO ATC/DDD Index lists A06AH02 alvimopan without assigning a defined daily dose, reflecting its short‑term, procedure‑linked use rather than chronic therapy.atcddd.fhi+1

General toxicological profile

Alvimopan’s adverse effects are primarily gastrointestinal, including abdominal pain, distension, constipation or diarrhea, flatulence, nausea and vomiting; most events are mild to moderate and occur early in the post‑operative course.pubmed.ncbi.nlm.nih+4
Non‑gastrointestinal adverse reactions can include anemia, dyspepsia, urinary disturbances, back pain and, less commonly, cardiovascular events; due to a signal of increased myocardial infarction risk in long‑term OIC studies, alvimopan is now limited to short‑term inpatient use for postoperative ileus under specific risk management programs.pubmed.ncbi.nlm.nih+4
Pre‑ and postnatal development studies in rats (intravenous dosing from gestation day 7 through lactation day 20) did not show adverse effects on offspring development at tested doses, although drug and metabolite were measurable in maternal milk.dailymed.nlm.nih+2

Lactation‑toxicology considerations

Regulatory labeling indicates that alvimopan and its metabolite are detected in the milk of lactating rats, demonstrating excretion into mammalian milk.accessdata.fda+1
At an intravenous dose of 10 mg/kg/day in animal models, milk concentrations of alvimopan and its metabolite were approximately 15‑fold and 0.11‑fold of maternal plasma levels, respectively, at one hour post‑dose, suggesting potentially significant exposure for nursing offspring in that species.drugs
For humans, product information states that it is unknown whether alvimopan is excreted into breast milk and there are no data on effects in breastfed infants or on milk production; manufacturers and secondary references therefore advise either discontinuing breastfeeding or discontinuing the drug, weighing the importance of the medicine to the mother.accessdata.fda+3

On a mechanistic basis, alvimopan is a small, orally active molecule with meaningful systemic exposure, and if present in human milk it would likely be orally absorbed by the infant, potentially antagonizing opioid receptors in the gastrointestinal tract and possibly systemically. This raises theoretical concerns about interference with analgesia if the infant receives opioids, alteration of gut motility or secretion, and unknown long‑term developmental implications. Given the absence of human lactation pharmacokinetic data and clinical case series, major drug information sources classify alvimopan as a medicine to be used with caution in breastfeeding women, favoring avoidance when alternative strategies are available.drugs+4

Clinical use in breastfeeding women

Alvimopan is used for a very short duration in the immediate postoperative period after bowel resection, often in women of mixed reproductive status, but specific experience in breastfeeding patients is not documented.drugbank+4
In a lactating woman needing bowel resection, preferred approaches include optimizing perioperative management with non‑pharmacological measures and considering the temporary interruption of breastfeeding if alvimopan is judged essential for postoperative recovery. When therapy is used in a nursing mother, expert sources recommend caution, individualized risk–benefit assessment, and close monitoring of the infant for gastrointestinal symptoms or signs of opioid receptor antagonism, even though concrete infant risk estimates are unavailable.mayoclinic+5

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