Neuromodulation using antidepressant drugs in irritable bowel syndrome
Many drugs classed as antidepressants, including tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) can be used for their brain–gut neuromodulatory effects (rather than their antidepressant effects) in irritable bowel syndrome (IBS).
There is some evidence that TCAs and SSRIs reduce visceral hypersensitivity in IBS, which improves abdominal pain, and also appears to provide global symptom relief. Reassure the patient that the benefit is not restricted to people with anxiety or depression.
The choice of neuromodulator therapy should be individualised and primarily depends on the symptoms (eg abdominal pain, constipation). Also consider comorbidities, concurrent medications, adverse effect profile of the neuromodulator, patient preference, contraindications and concurrent psychiatric disorders. In patients with coexisting anxiety or depression, higher dosages or a different antidepressant drug may be indicated. See the Psychotropic guidelines for information about the management of anxiety and depression.
A TCA should be tried first; suitable regimens include:
1amitriptyline 5 to 10 mg orally, at night initially. Increase every 7 days, as tolerated and according to response, up to 50 mg at night amitriptyline amitriptyline amitriptyline
OR
1nortriptyline 5 to 10 mg orally, at night initially. Increase every 7 days, as tolerated and according to response, up to 50 mg at night. nortriptyline nortriptyline nortriptyline
Doses of TCAs for IBS are generally lower than the doses used to treat anxiety or depression; despite this, adverse effects (eg drowsiness, dry mouth, constipation) may limit patient adherence.
If symptoms persist despite using an optimal dose for at least 4 weeks (full benefit may take 3 months or longer), stop the TCA—for advice, see Gradual dose reduction to stop an antidepressant. If symptoms have improved, the dose should be adjusted to determine the optimal dose based on symptoms and adverse effects.
If a TCA is contraindicated, ineffective or causes adverse effects, or if anxiety or depression is prominent, consider using an SSRI instead. In these patients use an SSRI at the usual dosage for anxiety or depression.
If symptoms persist despite the use of a TCA or an SSRI, consider referral to a gastroenterologist. While awaiting referral, trial of another antidepressant drug such as an SNRI (eg duloxetine) or mirtazapine may be considered; however, evidence to support their use is limitedDrossman, 2018.