How should functional abdominal pain be managed in an adult without red‑flag symptoms?

Management of Functional Abdominal Pain in Adults Without Red-Flag Symptoms

For adults with functional abdominal pain without alarm features, initiate low-dose tricyclic antidepressants (starting amitriptyline 10 mg at bedtime, titrating to 30-50 mg) as the primary pharmacologic intervention, combined with patient education about gut-brain interaction and cognitive behavioral therapy for those with moderate-to-severe symptoms or impaired quality of life. 1, 2

Initial Diagnostic Approach

• Establish the diagnosis clinically based on chronic or recurrent abdominal pain (≥3 months) without structural explanation, avoiding exhaustive testing that delays treatment initiation 1, 2
• Perform limited investigations including complete blood count, coeliac serology (especially if overlapping bowel symptoms), and plain abdominal radiography during acute episodes to exclude obstruction 1, 2
• Reserve additional imaging (small bowel series, CT scan) only for patients with changing symptom patterns, severe symptoms, or specific demographic risk factors 1, 2

Establishing the Therapeutic Relationship

• Explain that functional abdominal pain represents a disorder of gut-brain interaction involving altered pain processing, visceral hypersensitivity, and central sensitization—not a psychological condition or "all in their head" 1, 3
• Assure patients of your continued involvement and commitment to working collaboratively, as this therapeutic alliance is foundational to successful outcomes 1
• Avoid repetitive testing once the functional diagnosis is established, as this reinforces illness behavior and increases healthcare costs without benefit 1, 4

First-Line Pharmacologic Treatment

• Start low-dose tricyclic antidepressants as the primary medication for abdominal pain, beginning with amitriptyline 10 mg at bedtime and titrating every 2-3 weeks to 30-50 mg based on response and tolerability 1, 2
• Emphasize to patients that TCAs work through neuromodulation of pain pathways in the brain and spinal cord at doses lower than those needed for depression, with analgesic effects typically appearing within 1-3 weeks 1, 2
• Alternative neuromodulators include serotonin-norepinephrine reuptake inhibitors (SNRIs) such as duloxetine or venlafaxine, or mirtazapine, though evidence is strongest for TCAs 1, 3

Antispasmodic Therapy

• Consider antispasmodic medications (anticholinergics such as hyoscyamine or dicyclomine) as adjunctive therapy, particularly when pain is clearly meal-related or cramping in nature 1, 5, 6
• Peppermint oil can be used as a natural antispasmodic option with demonstrated efficacy for cramping abdominal pain 6, 7
• Antispasmodics provide symptomatic relief but do not address underlying pain sensitization, making them best suited for mild symptoms or as adjuncts to neuromodulators 1, 7

Psychological and Behavioral Interventions

• Initiate cognitive behavioral therapy (CBT), gut-directed hypnotherapy, or mindfulness-based stress reduction for patients with moderate-to-severe symptoms, impaired quality of life, or poor response to initial pharmacotherapy 1
• These brain-gut behavioral therapies target pain catastrophizing, maladaptive coping, and central pain amplification, with evidence showing sustained benefit for abdominal pain and overall function 1, 6
• Psychological interventions work best when symptoms relate to identifiable stressors, when anxiety or depression coexist, or when symptoms are of shorter duration with waxing-waning patterns 1, 3

Lifestyle and Self-Management Strategies

• Encourage regular aerobic physical activity, which improves pain symptoms and overall quality of life through multiple mechanisms including reduced visceral hypersensitivity 1, 8
• Provide education on sleep hygiene, mindful eating practices, and stress management techniques to enhance patient self-efficacy and symptom control 1, 3
• Avoid overly restrictive diets that may lead to nutritional deficiency or disordered eating; instead, help patients identify and moderately limit specific trigger foods through systematic trial 1

Dietary Considerations

• For patients with overlapping bowel symptoms (bloating, altered stool pattern), consider referral to a gastroenterology dietitian for structured dietary counseling 1, 2
• A low FODMAP diet may be appropriate for those with moderate-to-severe gastrointestinal symptoms alongside pain, but must be delivered by a trained dietitian to prevent nutritional inadequacy 1, 6
• Standard dietary advice includes adequate fiber intake (25 g/day), though evidence for pain reduction specifically is mixed 1, 8

Management of Refractory Cases

• For patients unresponsive to first-line TCA therapy, consider combination neuromodulation (e.g., TCA plus SNRI or gabapentinoid) while monitoring for serotonin syndrome 1, 3
• Refer to a multidisciplinary pain management program for severe, refractory symptoms with significant functional impairment, involving gastroenterology, psychology, dietetics, and pain specialists 1
• Mood stabilizers (gabapentin, pregabalin) or atypical antipsychotics (quetiapine) should only be considered with psychiatric consultation for intractable cases 1, 3

Critical Medications to Avoid

• Never prescribe opioids for functional abdominal pain, as they worsen dysmotility, create hyperalgesia, risk narcotic bowel syndrome, and provide no long-term benefit 1, 8
• Avoid benzodiazepines due to high dependence risk and lack of efficacy for visceral pain 1, 2
• Discontinue cyclizine if used chronically, particularly in patients with intravenous access, due to addiction potential and vein damage 1

When to Escalate or Refer

• Refer to gastroenterology when diagnostic uncertainty persists, symptoms prove refractory to 6-8 weeks of appropriate first-line therapy, or the patient requests specialist input 1, 2
• Refer to gastropsychology or psychiatry for moderate-to-severe depression/anxiety, suicidal ideation, suspected eating disorders, or concern about medication misuse 1, 9
• Re-evaluate patients 3-6 weeks after initiating treatment to assess response and adjust the management plan accordingly 1, 2

Common Pitfalls to Avoid

• Do not pursue exhaustive imaging or endoscopic evaluation in young patients without alarm features, as this delays effective treatment and reinforces illness behavior 1, 4
• Do not use low-dose TCAs (10-30 mg) to treat comorbid major depression or anxiety disorders, as these doses are insufficient for psychiatric benefit; use therapeutic-dose SSRIs (e.g., sertraline 50-200 mg) instead 1, 9
• Do not implement restrictive diets without dietitian supervision, especially in patients with weight loss, nutritional deficiency, or psychological comorbidities suggesting eating pathology 1, 2
• Avoid surgical interventions for functional abdominal pain, as they carry high risk of iatrogenic harm without addressing the underlying pain mechanism 1, 2