Is Bentyl (Dicyclomine) Contraindicated in Constipation?
Bentyl (dicyclomine) is not absolutely contraindicated in constipation, but it should be used with extreme caution and is best avoided when constipation is a major feature, as its anticholinergic effects can worsen constipation and potentially lead to serious complications.
FDA-Labeled Contraindications
Dicyclomine is formally contraindicated in patients with 1:
- Obstructive disease of the gastrointestinal tract
- Severe ulcerative colitis
- Reflux esophagitis
- Unstable cardiovascular status in acute hemorrhage
- Myasthenia gravis
- Glaucoma
- Obstructive uropathy
Constipation itself is not listed as an absolute contraindication, but the drug's mechanism of action directly causes constipation as a predictable adverse effect 1.
Mechanism and Clinical Concerns
Why Dicyclomine Worsens Constipation
Dicyclomine's anticholinergic action reduces gastrointestinal tone and motility, directly leading to constipation 1. The FDA label explicitly states that anticholinergic drugs cause "reduction in the tone and motility of the gastrointestinal tract leading to constipation" 1.
Serious Complications to Avoid
In patients with existing constipation, dicyclomine can precipitate dangerous complications 1:
- Paralytic ileus - Large doses may suppress intestinal motility completely
- Toxic megacolon - Particularly dangerous in patients with ulcerative colitis 1
- Ogilvie's syndrome (colonic pseudo-obstruction) - Rarely reported but serious 1
- Intestinal obstruction - Diarrhea may be an early symptom of incomplete obstruction, and treating with dicyclomine would be "inappropriate and possibly harmful" 1
Guideline Recommendations
British Society of Gastroenterology (2000 & 2021)
Tricyclic antidepressants (which share anticholinergic properties) "are best avoided if constipation is a major feature" 2. This same principle applies to dicyclomine, which has even more pronounced anticholinergic effects.
The 2000 BSG guidelines note that constipation was the most significant side effect of tricyclic antidepressants in IBS trials 2.
Clinical Context for Use
Dicyclomine is indicated for IBS with diarrhea or pain-predominant IBS, not constipation-predominant IBS 2:
- The 2000 BSG guidelines recommend antispasmodics with anticholinergic action (including dicyclomine) for reducing pain in IBS 2
- However, they explicitly state these should be avoided when constipation is prominent 2
- The 2022 AGA guidelines note that "regular use in constipation may be limited due to its anticholinergic effects" 2
Clinical Decision Algorithm
When to AVOID Dicyclomine:
- Constipation-predominant IBS - Choose alternative therapies 2
- Any patient with significant baseline constipation - Risk of worsening symptoms 1
- Elderly patients with constipation - Higher susceptibility to anticholinergic effects 1
- Patients taking other constipating medications (opioids, other anticholinergics) - Additive effects 3
When Dicyclomine May Be Used (with caution):
- Diarrhea-predominant IBS with abdominal pain - Primary indication 2, 4
- Pain-predominant IBS without constipation - For postprandial cramping 2, 5
- Mixed IBS during diarrheal phases - Intermittent use only 4, 5
Monitoring Requirements if Used:
- Assess bowel movement frequency before and during treatment 1
- Discontinue immediately if constipation develops or worsens 1
- Watch for abdominal distension, which may signal developing ileus 1
Alternative Therapies for Constipation-Predominant IBS
Instead of dicyclomine, use 2:
- Linaclotide (guanylate cyclase-C agonist) - Strong evidence, most efficacious for IBS-C 2
- Lubiprostone (chloride channel activator) - Strong evidence, less diarrhea than linaclotide 2
- Tenapanor (sodium-hydrogen exchange inhibitor) - Strong evidence 2
- Plecanatide or tegaserod - Alternative secretagogues 2
Common Pitfalls to Avoid
- Do not prescribe dicyclomine for "IBS" without specifying subtype - It will harm constipation-predominant patients 2
- Do not combine with other anticholinergic drugs - Increases risk of severe constipation 3
- Do not ignore early constipation symptoms - May progress to serious complications 1
- Do not use in elderly without careful assessment - Higher risk of anticholinergic burden 1, 3