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RCT: Low-Dose Amitriptyline Effective as Second-Line Treatment for Irritable Bowel Syndrome

20 Oct, 2024 | 15:56h | UTC

Background: Most patients with irritable bowel syndrome (IBS) are managed in primary care. When first-line therapies—such as dietary changes and antispasmodic drugs—are ineffective, the UK National Institute for Health and Care Excellence (NICE) recommends considering low-dose tricyclic antidepressants as second-line treatment. However, their effectiveness in primary care is uncertain, and they are infrequently prescribed in this setting.

Objective: To determine whether titrated low-dose amitriptyline is effective as a second-line treatment for IBS in primary care.

Methods: In a randomized, double-blind, placebo-controlled, phase 3 trial (ATLANTIS) conducted at 55 general practices in England, 463 adults aged 18 years or older with Rome IV IBS and ongoing symptoms despite first-line therapies were randomized 1:1 to receive low-dose oral amitriptyline (10 mg once daily) or placebo for 6 months. Dose titration over 3 weeks up to 30 mg once daily was allowed according to symptoms and tolerability. The primary outcome was the IBS Severity Scoring System (IBS-SSS) score at 6 months. Secondary outcomes included subjective global assessment (SGA) of relief of IBS symptoms, adequate relief for at least 50% of weeks, and adverse events.

Results: Among 463 participants (mean age 48.5 years; 68% female), low-dose amitriptyline was superior to placebo at 6 months, with a significant mean difference in IBS-SSS score between groups (–27.0; 95% CI, –46.9 to –7.1; P = .0079). More participants reported relief of IBS symptoms with amitriptyline compared to placebo (61% vs 45%; odds ratio [OR] 1.78; 95% CI, 1.19–2.66; P = .0050). Adequate relief of IBS symptoms for at least 50% of weeks was higher with amitriptyline (41% vs 30%; OR 1.56; 95% CI, 1.20–2.03; P = .0008). Adverse events were more frequent with amitriptyline, mainly related to anticholinergic effects such as dry mouth (54%) and drowsiness (53%), but most were mild. Withdrawals due to adverse events were slightly higher with amitriptyline (13% vs 9%).

Conclusions: Low-dose amitriptyline was superior to placebo as a second-line treatment for IBS in primary care and was safe and well tolerated.

Implications for Practice: General practitioners should consider prescribing low-dose amitriptyline to patients with IBS whose symptoms do not improve with first-line therapies, providing appropriate support for patient-led dose titration.

Study Strengths and Limitations: Strengths include the large sample size, primary care setting, and extended treatment duration. Limitations involve underrepresentation of patients with IBS with constipation, potential unblinding due to side effects, and a predominantly White participant population.

Future Research: Further trials assessing amitriptyline as a first-line therapy for IBS in primary care and studies on long-term outcomes are recommended.

Reference: Ford AC, Wright-Hughes A, Alderson SL, et al. Amitriptyline at Low-Dose and Titrated for Irritable Bowel Syndrome as Second-Line Treatment in Primary Care (ATLANTIS): a Randomised, Double-Blind, Placebo-Controlled, Phase 3 Trial. Lancet. 2023; DOI: http://doi.org/10.1016/S0140-6736(23)01523-4

 


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