Can long-term use of Bentyl (dicyclomine) cause diarrhea?

Long-Term Bentyl (Dicyclomine) Use and Diarrhea

No, long-term use of Bentyl (dicyclomine) does not typically cause diarrhea. In fact, constipation is more commonly reported as a side effect of this medication. 1

Mechanism of Action and Expected Side Effects

• Bentyl (dicyclomine) is an anticholinergic medication that works by inhibiting muscarinic receptors within the autonomic nervous system, which typically reduces intestinal motility 1
• The most common side effects of dicyclomine are anticholinergic in nature, including dry mouth (33%), dizziness (40%), blurred vision (27%), and nausea (14%) 1
• Constipation, not diarrhea, is listed as a common gastrointestinal adverse reaction in the FDA drug label for dicyclomine 1

Evidence on Dicyclomine and Bowel Function

• In clinical trials involving patients with irritable bowel syndrome, dicyclomine has been shown to improve bowel habits and decrease abdominal pain rather than cause diarrhea 2
• The FDA drug label specifically lists constipation among the gastrointestinal disorders associated with dicyclomine use 1
• Anticholinergic medications as a class generally slow intestinal transit time, which typically leads to constipation rather than diarrhea 1, 3

Medications Known to Cause Diarrhea

• More than 700 drugs have been implicated in causing diarrhea, with the most common being antimicrobials (accounting for 25% of drug-induced diarrhea), laxatives, magnesium-containing antacids, and nonsteroidal anti-inflammatory drugs 3
• Medications with cholinergic (not anticholinergic) properties are more likely to cause diarrhea by increasing intestinal motility 3
• Certain medication classes like anthraquinone-related agents, alpha-glucosidase inhibitors, and lipase inhibitors are known to commonly cause diarrhea 3

Management Considerations

• If a patient on long-term dicyclomine therapy develops diarrhea, other causes should be investigated as this would be unusual for this medication 3, 4
• Potential causes to consider include:
  • Other medications the patient may be taking 3
  • Infectious causes of diarrhea 5
  • Dietary factors or underlying gastrointestinal conditions 5
  • Bile acid diarrhea, which may require specific treatment 5

Clinical Implications

• If diarrhea occurs in a patient taking dicyclomine, it is important to rule out other causes rather than assuming it is medication-related 5
• For persistent diarrhea, management options include loperamide for symptomatic relief and ensuring adequate hydration 5, 6
• Severe diarrhea persisting more than 48 hours despite management requires medical attention 5

In conclusion, if a patient on long-term dicyclomine develops diarrhea, the medication is unlikely to be the cause, and other etiologies should be investigated.