Dicyclomine is classified as a high-risk medication primarily because of its strong anticholinergic properties, which can cause a wide range of serious side effects affecting the brain, gut, heart, and urinary system. The American Geriatrics Society places it on the Beers Criteria list of potentially inappropriate medications for older adults, with a strong recommendation to avoid it. Beyond age-related concerns, the drug carries risks for infants, people with certain medical conditions, and anyone taking other medications that amplify its effects.
How Dicyclomine Works in the Body
Dicyclomine is an antispasmodic drug commonly prescribed for irritable bowel syndrome (IBS). It works by blocking a chemical messenger called acetylcholine, which normally triggers muscle contractions in the gut and stimulates glands throughout the body. By blocking acetylcholine, dicyclomine relaxes intestinal muscles and reduces cramping.
The problem is that acetylcholine doesn’t just operate in your gut. It plays a role in nearly every organ system: your brain, eyes, bladder, sweat glands, and heart all rely on it. When dicyclomine suppresses acetylcholine broadly, it produces effects far beyond the intestines. This is the root of why the medication carries so many risks.
The Anticholinergic Side Effect Profile
The most common side effects are dry mouth, dry eyes, blurred vision, constipation, and difficulty urinating. These are uncomfortable but generally manageable at low doses. What makes dicyclomine high-risk is that these effects can escalate into dangerous territory, especially at higher doses or in vulnerable populations.
At higher doses, dicyclomine can cross into the central nervous system and cause confusion, disorientation, hallucinations, agitation, slurred speech, and delirium. One documented case involved a young woman who developed hallucinations, euphoria, short-term memory loss, and episodes of altered behavior after prolonged use. She was eventually admitted to a hospital in a confused state with disorientation, difficulty speaking, and loss of coordination. These aren’t typical side effects people expect from a stomach medication.
A cluster of symptoms known as anticholinergic toxicity can develop when the drug’s effects overwhelm the body. The hallmarks include a flushed face, dry and hot skin, blurred vision, confusion, rapid or irregular heartbeat, inability to urinate, and severe constipation. Because the drug suppresses sweating, it also raises the risk of heat exhaustion and heat stroke, particularly in warm environments or during physical activity.
Why It’s Flagged for Older Adults
The Beers Criteria, maintained by the American Geriatrics Society, is a widely used guide that identifies medications considered potentially inappropriate for people 65 and older. Dicyclomine appears on this list with a strong recommendation to avoid it, based on moderate-quality evidence. The rationale is straightforward: the drug is highly anticholinergic, and its effectiveness is uncertain.
Older adults are especially vulnerable to anticholinergic drugs for several reasons. Their bodies process and eliminate medications more slowly, so the drug lingers longer and reaches higher concentrations. Their brains are more sensitive to acetylcholine disruption, making confusion, falls, and cognitive decline more likely. Many older adults already take other medications with anticholinergic effects, and stacking these drugs together multiplies the risk. The Beers Criteria recommends avoiding dicyclomine entirely except in short-term palliative care settings where it may be used to reduce oral secretions.
Serious Gastrointestinal Complications
Ironically, a drug prescribed for gut problems can create far worse ones. Dicyclomine can suppress intestinal motility so much that the bowel essentially stops moving, a condition called paralytic ileus. In people with ulcerative colitis, this can trigger toxic megacolon, a life-threatening emergency where the colon rapidly dilates and can perforate.
There have also been reports of Ogilvie’s syndrome, a condition that mimics a complete bowel obstruction with all the pain, distension, and imaging findings of a blockage, but without any physical blockage present. The drug is contraindicated in people with existing gastrointestinal obstruction. For patients with an ileostomy or colostomy, diarrhea may actually be an early warning sign of an incomplete obstruction, and using dicyclomine in that situation could mask the symptom and prove fatal.
Dangers for Infants
Dicyclomine is contraindicated in infants under 6 months of age. The FDA label carries this warning because administration of the drug to infants has been followed by serious respiratory symptoms including shortness of breath, respiratory collapse, and apnea (where breathing stops entirely). Seizures, loss of consciousness, extreme muscle weakness, and coma have also been reported. Deaths have occurred. This is one of the clearest safety boundaries for the drug, and it exists because infants’ immature nervous systems are acutely sensitive to anticholinergic effects.
A Long List of Contraindications
Dicyclomine interacts with at least 18 medical conditions, which is unusually high for a single medication. People with any of the following conditions face elevated risk:
- Glaucoma: The drug can trigger acute narrow-angle glaucoma by increasing pressure inside the eye.
- Urinary obstruction: By relaxing the bladder muscle, dicyclomine can make it impossible to urinate, leading to acute urinary retention.
- Myasthenia gravis: This autoimmune condition already involves impaired nerve-muscle communication, and blocking acetylcholine further worsens muscle weakness.
- Coronary artery disease or hypertension: The drug’s effect on heart rate can be dangerous in people with cardiovascular conditions.
- Psychoses: Anticholinergic drugs can worsen psychiatric symptoms.
- Severe ulcerative colitis or GI obstruction: Risk of paralytic ileus and toxic megacolon, as described above.
- Liver or kidney impairment: Reduced ability to clear the drug from the body increases the chance of toxicity.
Autonomic neuropathy, hyperthyroidism, acid reflux, and fever also appear on the list of conditions that make the drug riskier to use.
The Compounding Effect of Other Medications
Many commonly prescribed drugs also have anticholinergic properties, including certain antihistamines, antidepressants, sleep aids, and bladder medications. When dicyclomine is combined with any of these, the anticholinergic burden on the body adds up. This is sometimes called “anticholinergic stacking,” and it dramatically increases the likelihood of toxicity. A person who tolerates each drug individually may experience confusion, dangerous heart rate changes, or inability to urinate when the drugs are combined.
This stacking effect is a major reason dicyclomine is flagged as high-risk rather than simply “use with caution.” For older adults in particular, who may already be taking several medications with mild anticholinergic effects, adding dicyclomine can push the total anticholinergic load past a tipping point.
Signs of Toxicity to Watch For
If you or someone you’re caring for takes dicyclomine, the warning signs of anticholinergic toxicity follow a recognizable pattern: the skin becomes flushed and dry, the mouth dries out, vision blurs, the heart races, urination becomes difficult or stops, and mental status changes. Confusion, agitation, or hallucinations are red flags that the drug’s effects have reached the brain. Inability to sweat in a warm environment is another danger signal, as the body loses its primary cooling mechanism. These symptoms can develop gradually with regular use or suddenly with an accidental overdose.