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# Drugs for irritable bowel syndrome

Gut-targeted drugs for IBS with diarrhoea: a 5-HT3 blocker (alosetron) and a mixed opioid-receptor drug (eluxadoline).

Updated Nov 1, 2026

## What they are

Medicines for irritable bowel syndrome when diet, fibre, antispasmodics and loperamide are not enough. This page groups the diarrhoea-predominant (IBS-D) agents that act on gut receptors; drugs for constipation-predominant IBS (linaclotide, plecanatide, lubiprostone) are on the laxatives page.

## Mechanism of action

IBS involves visceral hypersensitivity and abnormal motility. Alosetron blocks 5-HT3 cation channels on enteric neurons, which slows colonic transit and dampens visceral pain. Eluxadoline acts on gut opioid receptors (mu and kappa agonist, delta antagonist) to slow transit and reduce pain locally.

Target: Enteric 5-HT3 receptors and gut opioid receptors

## Key points

- Alosetron is limited to women with severe IBS-D because of ischaemic colitis and serious constipation.
- Alosetron is stopped at once if constipation or signs of ischaemic colitis appear.
- Fluvoxamine (strong CYP1A2 inhibitor) is contraindicated with alosetron.
- Eluxadoline can cause sphincter of Oddi spasm and pancreatitis; avoided without a gallbladder, with biliary or pancreatic disease or heavy alcohol use.

## Drugs in this class

- [**Alosetron** A 5-HT3 blocker for women with severe IBS with diarrhoea that has not responded to other care. It can cause ischaemic… 5-HT3 receptor (ligand-gated cation channel) on enteric neurons](https://durgical.com/en/pharmacology/alosetron/)
- [**Eluxadoline** A gut-acting opioid-receptor drug for IBS with diarrhoea in adults. It can cause pancreatitis, mainly in people… Mu and kappa opioid receptors (agonist), delta opioid receptor (antagonist) in the gut](https://durgical.com/en/pharmacology/eluxadoline/)

## Others in the class

- Rifaximin (non-absorbed antibiotic, other antibacterials page)
- Antispasmodics: dicycloverine, hyoscine butylbromide
- Tenapanor (constipation-predominant IBS)

## Test yourself

Think of the answer, then tap the question to see it.

## Which serious complication limits alosetron use?

Ischaemic colitis (and serious complications of constipation).

## Which patients should not receive eluxadoline?

Those without a gallbladder, with biliary obstruction, sphincter of Oddi disease, past pancreatitis or heavy alcohol use.

## Which receptor does alosetron block?

The 5-HT3 receptor, a ligand-gated cation channel.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - ALOSETRON HYDROCHLORIDE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d62b2c5a-1693-4e67-96d5-197e1fdc8694) (DailyMed (U.S. National Library of Medicine), 2025); [Eluxadoline: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a615054.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=A03AE) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Source: https://durgical.com/en/pharmacology/classes/drugs-for-irritable-bowel-syndrome/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/drugs-for-irritable-bowel-syndrome/