1. Clinical Overview
Dicyclomine hydrochloride is an anticholinergic/antispasmodic agent used primarily for the treatment of functional bowel/irritable bowel syndrome (IBS) and other conditions involving smooth muscle spasm of the gastrointestinal tract. It is a tertiary amine with direct smooth muscle relaxant properties in addition to its antimuscarinic effects.
| Onset | Duration | Bioavailability |
|---|---|---|
| 1-2 hours (oral) | Approximately 4-6 hours | ~67% (oral) |
2. Mechanism of Action
Dicyclomine exerts a dual mechanism: 1) Competitive antagonism of muscarinic acetylcholine receptors (M1, M2, M3) at postganglionic parasympathetic neuroeffector sites, blocking the action of acetylcholine. 2) A direct papaverine-like spasmolytic action on smooth muscle, independent of its anticholinergic activity. This relaxes smooth muscle in the gastrointestinal tract, biliary tract, uterus, and ureter.
3. Indications & Uses
- Symptomatic relief of Irritable Bowel Syndrome (IBS)
- Treatment of functional bowel/intestinal disorders (e.g., spastic colon, mucous colitis)
4. Dosage & Administration
Adult Dosage: Usual dose: 10-20 mg, 3-4 times daily. For IBS: Start with 10 mg QID and titrate up to 20 mg QID if needed and tolerated. Maximum: 160 mg/day in divided doses.
Administration: Take orally, usually 30 minutes to 1 hour before meals and at bedtime. Tablet should be swallowed whole with a glass of water. Can be taken with or without food, but taking before meals may improve efficacy for GI spasms. Do not crush or chew.
5. Side Effects
Common side effects may include:
- Dry mouth (xerostomia)
- Blurred vision
- Dizziness
- Drowsiness/sedation
- Nausea
- Constipation
- Weakness
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other Anticholinergics (e.g., Atropine, Hyoscine, Tricyclic Antidepressants, Antihistamines) | Additive anticholinergic side effects (dry mouth, constipation, urinary retention, confusion). | Major |
| Potassium Chloride (wax-matrix formulations) | Increased risk of GI mucosal lesions/ulceration due to reduced GI motility. | Moderate |
| Metoclopramide | Pharmacological antagonism; dicyclomine reduces GI motility, counteracting metoclopramide's prokinetic effect. | Moderate |
| Amantadine | Increased anticholinergic side effects and risk of psychosis. | Moderate |
| Digoxin | Increased bioavailability of digoxin due to reduced GI motility, potentially leading to toxicity. | Moderate |
| CYP2C19 Inhibitors (e.g., Omeprazole, Fluconazole) | May increase dicyclomine plasma levels, increasing risk of toxicity. | Moderate |
| Alcohol, CNS Depressants (Benzodiazepines, Opioids) | Additive CNS depression (drowsiness, dizziness). | Moderate |
7. Patient Counselling
- DO take the medication exactly as prescribed, usually before meals and at bedtime.
- DO inform your doctor about all other medications you are taking.
- DO maintain adequate fluid intake to prevent constipation.
- DO use sugar-free gum or candies to relieve dry mouth.
- DO get regular eye check-ups if on long-term therapy.
- DONT drive or operate heavy machinery until you know how the medicine affects you.
- DONT take alcohol while on this medication.
- DONT stop the medication abruptly if taken for a long time; consult your doctor.
- DONT use in infants or children without pediatrician's strict advice.
8. Toxicology & Storage
Overdose: Symptoms are primarily due to exaggerated anticholinergic effects: CNS (restlessness, excitement, confusion, hallucinations, delirium, seizures, respiratory depression, coma), Cardiovascular (tachycardia, palpitations, hypertension followed by hypotension, circulatory failure), Peripheral (dry mouth, blurred vision, hyperthermia, flushed dry skin, urinary retention, decreased GI motility).
Storage: Store below 30°C, in a cool, dry place, protected from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.