There is no medication that can cure IBS. Treatments are always symptom-specific, helping patients to manage the condition. The medication prescribed by your GP can look completely different depending on whether you’re dealing with constipation, diarrhoea, or abdominal pain.

The most common IBS tablets like Buscopan and Mebeverine can be bought without a prescription. However, GPs have several alternative IBS medications in the UK for when these do not control symptoms.

Medication is only one part of how to treat IBS, and the right medication depends on whether your main symptoms are pain, diarrhoea, constipation, or a mixture of all three.

What Is the Best Medication for IBS?

There is no single best medication for IBS. Medications are matched to the main symptom:

• cramping/pain → antispasmodics such as mebeverine or Buscopan

• diarrhoea → loperamide

• constipation → laxatives, sometimes linaclotide

• persistent abdominal pain/global symptoms → low-dose amitriptyline

NICE specifically recommends a symptom-led approach. IBS is also a long-term condition, so no treatment will solve the problem forever.

Mebeverine and Buscopan for IBS Cramps

Mebeverine and Buscopan are antispasmodics. They help relax the muscles in the bowel to reduce IBS symptoms of cramping and abdominal pain.

Mebeverine is a smooth-muscle relaxant. It acts on the muscles of the bowel to relieve spasms, cramping, and abdominal pain. It can also have some effect on the frequency of bowel movements. Depending on the preparation, it’s available both over the counter (OTC) and via prescription.

Buscopan contains the active ingredient hyoscine butylbromide. It minimises the contractions of smooth muscle in the digestive tract and works relatively quickly for cramping. NHS guidance states that these IBS tablets can begin working within 15 minutes.

Peppermint tea is not a medication. However, some people with IBS find peppermint helpful for easing cramping.

Loperamide for IBS with Diarrhoea

Loperamide slows the passage of food through the bowel. This makes the food move more slowly, so the bowel has more time to absorb water, making stools firmer. It’s a common treatment for diarrhoea.

NICE considers loperamide as the first-choice antimotility treatment for diarrhoea in IBS. However, while it’s beneficial, there are some concerns about the effects of long-term use. The dosage should be adjusted according to stool consistency rather than simply taking a fixed amount indefinitely.

What Can Your GP Prescribe for IBS Constipation?

Laxatives are usually prescribed if you’re struggling with constipation. They come in several varieties:

• Macrogol – draws water into the bowel to soften stools and make them easier to pass.

• Ispaghula husk – a type of soluble fibre that bulks out stools and can make bowel movements more regular.

• Senna – stimulates the bowel muscles to help move stool along.

• Sodium picosulfate – encourages the bowel to contract and can help relieve constipation.

• Linaclotide – a prescription treatment for IBS with constipation that helps increase fluid in the bowel and makes stools easier to pass.

Lactulose is another option. However, NICE warns against using it for IBS because it can worsen bloating and other symptoms. Just as for diarrhoea, taking laxatives long-term is not recommended.

Amitriptyline for IBS Pain

Amitriptyline isn’t a traditional IBS medication. In fact, it is technically a tricyclic antidepressant. However, at lower doses, it’s commonly prescribed for other conditions.

Its benefit appears to involve modifying pain signalling, gut sensitivity, and possibly motility. It’s generally considered a second-line treatment when antispasmodics, laxatives, or loperamide have not worked.

The ATLANTIS trial looked at amitriptyline in 463 UK primary-care patients: 61.3% taking low-dose amitriptyline reported at least some relief after six months, compared with 45.1% receiving placebo.

It’s the best evidence we have for the effectiveness of amitriptyline for IBS.

What If IBS Medication Does Not Work?

IBS medication is not always effective because the underlying mechanisms behind IBS are not fully understood. Instead, treatment relies on managing symptoms. These medications can reduce symptoms, but they do not always control them entirely.

If that’s the case, it’s worth considering whether there is something else causing your symptoms.

There isn’t a single definitive test for IBS. An IBS diagnosis in the UK is generally based on the pattern of symptoms together with your medical history. However, investigations can help rule out other conditions, helping you come to an IBS diagnosis. These tests include blood tests, stool testing, and breath testing.

If IBS medication is not controlling your symptoms, further investigation may help identify what is driving them. Book an appointment with The Functional Gut Clinic for specialist diagnostic testing to investigate the cause of your IBS symptoms.

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