Gut, brain and sleep
Low-dose antidepressants for IBS and gut pain
Low doses of certain antidepressant medicines are prescribed for irritable bowel syndrome and functional dyspepsia because they reduce pain signalling between the gut and the brain. Doctors call them gut-brain neuromodulators. They are used for this effect on nerves, at doses below those used for depression, and a prescription does not mean that your doctor thinks you are depressed. In a trial of 463 people with IBS, a low-dose medicine of the tricyclic group gave better relief than a dummy tablet over six months.
In short
- These medicines act on the nerves that carry pain signals from the gut.
- They take four to eight weeks to show their full effect.
- Drowsiness and a dry mouth are the commonest side effects of the tricyclic group, and they often ease after the first two weeks.
- When a medicine helps, it is usually continued for six to twelve months and then reduced gradually.
This page explains why these medicines are used. Whether one is right for you is decided in a consultation.
What is a gut-brain neuromodulator?
A neuromodulator is a medicine that changes how nerves pass on signals. The gut and the brain use the same chemical messengers, including serotonin and noradrenaline. Medicines first developed for depression act on these messengers, and at low doses they act on the nerves of the gut.
Why would an antidepressant help the gut?
- It lowers pain signalling. Signals from an over-sensitive gut are damped on their way to the brain.
- It changes gut movement. The tricyclic group slows the bowel, which helps when diarrhoea is the main problem.
- It improves sleep. Some of these medicines are taken at night and deepen sleep, which itself lowers gut sensitivity.
Three ways it helps. These medicines act on the nerves that carry pain signals from the gut. At low doses they act on the nerves of the gut.
Which types are used?
| Group | Mainly used for | Common side effects |
|---|---|---|
| Tricyclic group | Abdominal pain, IBS with diarrhoea, functional dyspepsia | Drowsiness, dry mouth, constipation |
| SNRI group | Abdominal pain, especially with other long-term pain | Nausea at the start, sweating |
| SSRI group | IBS when anxiety or low mood is prominent. It has less effect on pain. | Nausea, loose stools or restlessness at the start |
| Medicines that help the stomach to relax | Early fullness, nausea and weight loss in functional dyspepsia | Drowsiness, increased appetite |
What does the evidence show?
- In a trial of 463 adults whose IBS had not improved with first-line treatment, a low-dose tricyclic medicine, adjusted by the patients themselves within a set range, gave lower symptom scores than a dummy tablet at six months. Side effects were mostly mild.
- American guidelines recommend the tricyclic group for the overall symptoms of IBS, and suggest it for functional dyspepsia that has not responded to acid-reducing treatment.
- A Rome Foundation report sets out which medicine suits which pattern of symptoms, and advises continuing an effective medicine for six to twelve months.
What should I expect?
A low starting dose, usually at night
The dose is raised in small steps if needed.
Side effects first, benefit later
Drowsiness or a dry mouth can appear in the first days. Relief of pain builds over four to eight weeks.
A review
If there is no benefit after an adequate trial, the medicine is changed or stopped.
A planned course
When it helps, it is continued for six to twelve months and then reduced slowly. Do not stop it suddenly.
Side effects first, benefit later. Drowsiness or a dry mouth can appear in the first days, and they often ease after the first two weeks. Relief of pain builds over four to eight weeks. This is a sketch of the usual pattern, not a set of measurements.
Who should take extra care?
Tell me if you have any of the following, because the choice of medicine may change:
- A heart rhythm problem or a recent heart attack
- Glaucoma
- An enlarged prostate or difficulty passing urine
- Epilepsy
- Bipolar disorder
- Pregnancy, or plans for one, or breastfeeding
- Other medicines that act on serotonin, including some pain and migraine medicines
Tell your doctor at once about any worsening of mood or thoughts of self-harm.
Questions patients ask me
Does this mean my doctor thinks I am depressed?
No. The medicine is being used for its action on gut nerves. The dose is lower than the dose used to treat depression.
Are these medicines addictive?
No. They do not cause craving. They should be reduced gradually and not stopped abruptly, to avoid unpleasant symptoms on stopping.
How long before it works?
Some people notice better sleep and less pain within two weeks. The full effect takes four to eight weeks.
Will it make me sleepy or cause weight gain?
Drowsiness is common with the tricyclic group, which is why it is taken at night. Weight gain is less common at low doses. Tell me if either becomes a problem.
Can I take it with my other medicines?
Usually, but some combinations need care. Bring a list of everything you take, including supplements.
Can I stop once I feel better?
After six to twelve months of good control, we reduce the dose in steps. Many people stay well after stopping.
Is this the same as low-dose naltrexone?
No. Low-dose naltrexone is a different medicine that blocks opioid receptors. It has been studied mainly in Crohn’s disease, and the evidence for it is much thinner.
Sources
This page is written for patients and is based on the guidelines and studies below. It is for education and does not replace a consultation.
- Rome Foundation report on neuromodulators for gut-brain interaction disorders. Drossman DA et al. Gastroenterology. 2018. PubMed 29274869
- Trial of a low-dose tricyclic medicine for irritable bowel syndrome in primary care. Ford AC et al. Lancet. 2023. PubMed 37858323
- American College of Gastroenterology guideline on irritable bowel syndrome. Lacy BE et al. Am J Gastroenterol. 2021. doi:10.14309/ajg.0000000000001036
- American and Canadian guideline on the management of dyspepsia. Moayyedi P et al. Am J Gastroenterol. 2017. PubMed 28631728
- Rome IV overview of disorders of gut-brain interaction. Drossman DA. Gastroenterology. 2016. PubMed 27144617
- British Society of Gastroenterology guideline on irritable bowel syndrome. Vasant DH et al. Gut. 2021. PubMed 33903147