Neuromodulation using antidepressant drugs in functional gastrointestinal disorders
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 functional gastrointestinal disorders. Reassure the patient that the benefit is not restricted to patients with anxiety or depression.
Evidence to support the use of antidepressant drugs to manage functional gastrointestinal disorders is limitedDrossman, 2018. Most of the evidence is in the management of irritable bowel syndrome, but data has been extrapolated to the management of other functional gastrointestinal disorders.
There is evidence that use of a neuromodulator can improve abdominal pain, and appears to provide global symptom relief for functional gastrointestinal disorders.
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 functional gastrointestinal disorders 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 have not improved 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.