Dicyclomine, often recognized by its brand name Bentyl, is an antispasmodic medication primarily used to treat symptoms of Irritable Bowel Syndrome (IBS), such as cramping and muscle spasms in the gastrointestinal tract. While effective for managing these symptoms, its mechanism of action as an anticholinergic agent means it can have significant interactions with other drugs and substances. Understanding these interactions is crucial for patient safety and to ensure the medication works as intended. This guide details the major classes of substances you should avoid or use with extreme caution while taking dicyclomine.
Key Classes of Dicyclomine Interactions
Other Anticholinergic Medications
One of the most dangerous interactions involves taking dicyclomine with other medications that have anticholinergic properties. This combination can lead to a dangerously high level of anticholinergic activity in the body, overwhelming the system and causing severe side effects. The classic signs of anticholinergic toxicity include flushed skin, dry mouth, blurred vision, fever, and confusion.
Common examples include:
- Other antispasmodics: Hyoscyamine
- Antihistamines: Diphenhydramine (Benadryl)
- COPD medications: Ipratropium (Atrovent), tiotropium (Spiriva)
- Overactive bladder medications: Oxybutynin (Ditropan XL), solifenacin (Vesicare)
- Antipsychotics: Clozapine, chlorpromazine
- Tricyclic antidepressants (TCAs): Amitriptyline, doxepin
- Parkinson's disease medications: Amantadine
Central Nervous System (CNS) Depressants and Alcohol
Dicyclomine can cause side effects like drowsiness and dizziness. Mixing it with other CNS depressants or alcohol significantly amplifies these effects, increasing the risk of accidents and impairing judgment.
Substances to avoid include:
- Alcohol: Increases drowsiness and dizziness.
- Opioid pain relievers: Meperidine, morphine, oxycodone.
- Benzodiazepines: Clonazepam, diazepam, lorazepam.
- Muscle relaxants.
- Sleeping pills and sedatives.
- Cannabis (Marijuana).
Medications Affecting Gastrointestinal (GI) Motility
As an antispasmodic, dicyclomine works by slowing down gut motility. This directly counteracts the effects of medications designed to increase GI movement, rendering them less effective.
Interactions include:
- Metoclopramide (Reglan): Used for GERD and slowed stomach emptying.
- Erythromycin: Can be used off-label for gastroparesis.
- Tegaserod (Zelnorm): Used for IBS with constipation.
Antacids
Antacids can interfere with the absorption of dicyclomine, potentially making it less effective. To prevent this, healthcare providers recommend separating the administration of antacids and dicyclomine by at least two hours.
Glaucoma Medications
Dicyclomine is contraindicated in patients with glaucoma because it can increase intraocular pressure, potentially worsening the condition and counteracting the effects of glaucoma medication. Taking dicyclomine with drugs like timolol or latanoprost is not recommended.
Digoxin
Digoxin, a medication for heart failure, has a narrow therapeutic index, meaning small changes in its blood concentration can cause toxicity. Dicyclomine can increase digoxin levels in the blood, leading to a higher risk of side effects. Concurrent use is generally avoided or closely monitored.
Dicyclomine Interaction Comparison Table
| Interaction Type | Examples | Mechanism | Risk Profile |
|---|---|---|---|
| Additive Anticholinergic Effects | Antihistamines, TCAs, Antipsychotics, COPD meds, Overactive bladder meds | Intensifies anticholinergic side effects (dry mouth, constipation, blurry vision, confusion). | High - Can lead to anticholinergic toxicity, especially in older adults. |
| Additive CNS Depressant Effects | Alcohol, Opioids, Benzodiazepines, Muscle Relaxants | Significantly increases drowsiness, dizziness, and sedation. | High - Impairs mental alertness, increasing risk of falls and accidents. |
| Impaired Drug Absorption | Antacids (e.g., Tums, Maalox) | Reduces the absorption of dicyclomine, lowering its effectiveness. | Moderate - Can be managed by separating dosage times by at least two hours. |
| Antagonistic GI Motility Effects | Metoclopramide, Erythromycin | Dicyclomine's effect of slowing the gut counteracts the pro-motility effects of these drugs. | Moderate - Renders one or both medications less effective. |
| Increased Digoxin Toxicity | Digoxin (Lanoxin) | Increases serum concentrations of digoxin. | High - Poses risk of digoxin toxicity due to narrow therapeutic index. |
| Increased Risk of Heat Stroke | Topiramate, Extreme Heat | Dicyclomine decreases sweating, impairing the body's ability to cool itself. | High - Can cause life-threatening heatstroke, especially when combined with other risk factors. |
Dicyclomine Contraindications and Precautions
Beyond drug interactions, dicyclomine is not safe for everyone. It is contraindicated in infants under 6 months, nursing mothers, and individuals with a number of health conditions.
Conditions to consider include:
- Glaucoma: Specifically angle-closure glaucoma.
- Myasthenia gravis: A condition causing muscle weakness that dicyclomine can worsen.
- Obstructive GI or urinary tract diseases: Dicyclomine's slowing effect can exacerbate blockages.
- Severe ulcerative colitis: May lead to a severe complication called toxic megacolon.
- Reflux esophagitis: Inflammation of the esophagus.
- Unstable cardiovascular status.
- Severe liver or kidney disease: These conditions can slow the drug's clearance, increasing side effects.
How to Mitigate Interaction Risks
Managing the risk of drug interactions involves proactive communication and careful adherence to medical advice. Here are some strategies:
- Provide a complete medication list: Always inform your doctor and pharmacist of all medications, including over-the-counter (OTC) products, vitamins, nutritional supplements, and herbal products. This is the most crucial step.
- Separate dosing: For interactions that only affect absorption, such as with antacids, simply separate the dose times. For dicyclomine and antacids, taking the antacid at least two hours before or after dicyclomine can mitigate the issue.
- Avoid certain substances completely: Some interactions, like those with alcohol or other anticholinergics, require complete avoidance to prevent serious harm.
- Be aware of additive side effects: Be mindful of heightened drowsiness, dizziness, or confusion when combining dicyclomine with any other sedating medications. Avoid activities requiring mental alertness, like driving.
- Stay hydrated and cool: Given dicyclomine reduces sweating, it is essential to take precautions against overheating, especially in hot weather or during exercise.
Conclusion
Dicyclomine is an effective treatment for the gastrointestinal spasms associated with IBS, but it carries a significant risk of interaction with other medications and substances. From enhancing sedating effects when mixed with alcohol or CNS depressants to dangerously amplifying anticholinergic side effects, the potential for complications is high if not managed properly. Patients must maintain open communication with their healthcare providers, informing them of their full medication list to prevent harmful interactions. By understanding what not to mix with dicyclomine and adhering to prescribing guidelines, patients can minimize risks and ensure their safety and the treatment's efficacy.
