Medications for Abdominal Pain
Antispasmodics and tricyclic antidepressants are the most effective first-line and second-line treatments respectively for abdominal pain, particularly in irritable bowel syndrome (IBS). 1
First-Line Treatments
Antispasmodics
- Antispasmodics are the most commonly prescribed first-line medications for abdominal pain, particularly those with anticholinergic properties 1
- Specific antispasmodics include:
- Dicyclomine (anticholinergic): Shows significant improvement in pain but may cause dry mouth, visual disturbance, and dizziness 1, 2
- Hyoscine (anticholinergic): Effective for pain reduction 1
- Mebeverine and alverine citrate: Direct inhibitory effect on intestinal smooth muscle but less evidence for pain reduction specifically 1
- Common side effects include dry mouth, visual disturbances, and dizziness; anticholinergic side effects may limit use in some patients 1, 2
Other First-Line Options
- Peppermint oil: Considered a first-line treatment for abdominal pain in IBS with antispasmodic properties 1, 3
- Soluble fiber (ispaghula): Effective for global symptoms and abdominal pain in IBS; should be started at low dose (3-4g/day) and gradually increased 1
- Loperamide: Effective for diarrhea in IBS but may actually cause abdominal pain, bloating, and constipation as side effects 1
- NSAIDs (e.g., ibuprofen): May be used for short-term relief of abdominal pain but carry risks of gastrointestinal side effects including abdominal pain itself 4, 5
- Acetaminophen (paracetamol): May be suitable for mild to moderate acute abdominal pain with better gastrointestinal tolerability than NSAIDs 6, 7
Second-Line Treatments
Neuromodulators
- Tricyclic antidepressants (TCAs): Strong evidence as effective second-line treatment for abdominal pain in IBS 1
- Selective serotonin reuptake inhibitors (SSRIs): May be effective for global symptoms but less evidence specifically for pain 1
- Better option if constipation is present or if treating comorbid depression/anxiety 1
Specialized Treatments for IBS Subtypes
For IBS with diarrhea:
- 5-HT3 receptor antagonists (e.g., ondansetron): Highly efficacious for IBS with diarrhea; can be titrated from 4mg once daily to 8mg three times daily 1
- Eluxadoline (mixed opioid receptor drug): Effective for IBS with diarrhea but contraindicated in patients with sphincter of Oddi problems, cholecystectomy, alcohol dependence, pancreatitis, or severe liver impairment 1
- Rifaximin (non-absorbable antibiotic): Effective for IBS with diarrhea but limited effect on abdominal pain 1
- Cholestyramine: May help a small subset of patients with diarrhea-predominant IBS who have bile salt malabsorption 1
For IBS with constipation:
Severe or Refractory Abdominal Pain
- For severe cases, combination therapy (augmentation) may be considered, such as using multiple gut-brain neuromodulators together 1
- Vigilance for serotonin syndrome is required when combining certain medications, especially SSRIs and SNRIs 1
- Intramuscular hyoscine has been reported effective for severe or refractory abdominal pain 1
- Avoid opioids for chronic abdominal pain as they may lead to narcotic bowel syndrome and central sensitization 1
Important Considerations
- The cause of abdominal pain should be properly diagnosed before treatment, as medications differ based on underlying etiology 1, 8
- Abdominal wall pain is often overlooked but may respond to trigger point injections rather than oral medications 8
- Psychological factors significantly impact abdominal pain perception and medication efficacy 1
- Medications may be counterproductive in patients with major psychological problems as they may reinforce abnormal illness behavior 1
- For patients with IBS, a multidisciplinary approach including dietary modifications and psychological interventions should be considered alongside pharmacotherapy 1