Background: Irritable bowel syndrome, characterised by abdominal pain and a change in stool form or frequency, is most often managed in primary care. When first-line therapies are ineffective, National Institute for Health and Care Excellence guidelines suggest considering low-dose tricyclic antidepressants as second-line treatment, but their effectiveness in primary care is unknown and they are infrequently prescribed by general practitioners.
Objective: To evaluate the clinical and cost-effectiveness of low-dose titrated amitriptyline as a second-line treatment for irritable bowel syndrome in primary care.
Design: A pragmatic, randomised, multicentre, two-arm, double-blind, placebo-controlled trial. A nested, qualitative study explored participant and general practitioner experiences of treatments and trial participation, and implications for wider use of amitriptyline for irritable bowel syndrome in primary care. Participants, clinicians, investigators and analysts were masked to allocation.
Setting: Fifty-five general practices in three regions in England (Wessex, West of England, West Yorkshire).
Participants: Patients aged ≥ 18 years meeting Rome IV criteria for irritable bowel syndrome with ongoing symptoms after trying first-line treatments and no contraindications to TCAs.
Intervention: Amitriptyline 10 mg once-daily, self-titrated by participants to a maximum of 30 mg once-daily or matched placebo for 6 months. Participants randomised 1 : 1 with most having the option to continue blinded treatment for a further 6 months.
Main outcome measures: The primary participant-reported outcome was the effect of amitriptyline on global irritable bowel syndrome symptoms at 6 months, measured using the irritable bowel syndrome Severity Scoring System, with a 35-point between-group difference defined as the minimum clinically important difference. The key secondary outcome was the proportion of participants reporting subjective global assessment of relief at 6 months, defined as somewhat, considerable, or complete relief of symptoms. Other secondary outcomes included: effect on global symptoms, via the irritable bowel syndrome Severity Scoring System, and subjective global assessment of relief of irritable bowel syndrome symptoms at 3 and 12 months; effect on somatic symptom-reporting at 6 months; anxiety an-d depression scores; ability to work and participate in other activities at 3, 6 and 12 months; acceptability, tolerability and adherence to trial medication.
Results: Four hundred and sixty-three participants were randomised to amitriptyline (232) or placebo (231). An intention-to-treat analysis of the primary outcome showed a significant difference in favour of amitriptyline for irritable bowel syndrome Severity Scoring System score between arms at 6 months [-27.0, 95% confidence interval (CI) -46.9 to -7.10; p = 0.008]. For the key secondary outcome of subjective global assessment of relief of irritable bowel syndrome symptoms, amitriptyline was superior to placebo at 6 months (odds ratio 1.78, 95% CI 1.19 to 2.66; p = 0.005). Amitriptyline was superior to placebo across a range of other irritable bowel syndrome symptom measures but had no impact on somatoform symptom-reporting, anxiety, depression, or work and social adjustment scores. Adverse event trial withdrawals were more common with amitriptyline (12.9% vs. 8.7% for placebo) but most adverse events were mild. The qualitative study thematically analysed 77 semistructured interviews with 42 participants and 16 GPs. Most participants found the self-titration process acceptable and empowering.
Conclusions: General practitioners should offer low-dose amitriptyline to patients with irritable bowel syndrome whose symptoms do not improve with first-line therapies. Guidance and resources should support GP-patient communication to distinguish amitriptyline for irritable bowel syndrome from use as an antidepressant and to support patients managing their own dose titration.
Study registration: This trial is registered as ISRCTN48075063.
Funding: This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 16/162/01) and is published in full in Health Technology Assessment Vol. 28, No. 66. See the NIHR Funding and Awards website for further award information.
Keywords: ABDOMINAL PAIN; AMITRIPTYLINE; GENERAL PRACTICE; IRRITABLE BOWEL SYNDROME; OUTCOME ASSESSMENT; RANDOMISED CONTROLLED TRIAL.
People with irritable bowel syndrome experience stomach (abdominal) pain and changes to their bowel movements. Irritable bowel syndrome can have a serious impact on people’s lives. Previous small trials suggest that a drug called amitriptyline used at a low dose may help irritable bowel syndrome. Amitriptyline is already used to treat other conditions. It is available for irritable bowel syndrome but is not used much by general practitioners. We recruited adults aged ≥ 18 years with irritable bowel syndrome from UK general practices who did not have any issues preventing the use of amitriptyline. Patients received either low-dose amitriptyline or placebo (a dummy tablet) for 6 months. Patients could adjust the dose according to symptoms and side effects. Neither the researchers nor the patients knew which treatment they were getting. Participants recorded symptoms using a questionnaire containing an irritable bowel syndrome severity score. We looked at the difference in average irritable bowel syndrome severity score between patients receiving amitriptyline and placebo. We also looked at effects of amitriptyline on mood, ability to work, and non-gut symptoms related to irritable bowel syndrome, as well as safety and acceptability. Some patients and general practitioners were interviewed about their experiences. Four hundred and sixty-three patients took part. Participants receiving amitriptyline reported a bigger improvement in their irritable bowel syndrome severity scores at 6 months, compared with patients on placebo. Amitriptyline was better across a range of irritable bowel syndrome symptom measures but did not impact anxiety, depression or ability to work. Forty-six people (19.8%) stopped taking amitriptyline and 59 (25.5%) stopped the placebo before 6 months. Patients liked being able to adjust their dose and valued contact with the research team. This study showed that amitriptyline is more effective than a placebo and is safe. General practitioners should offer low-dose amitriptyline to people with irritable bowel syndrome if symptoms do not improve with other standard treatments. Patients should be supported and helped to adjust their dose as needed. The dose adjustment sheet used in this trial will be made available.