1. Clinical Overview
Dicyclomine hydrochloride is an antispasmodic and anticholinergic 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 acts as a competitive muscarinic acetylcholine receptor antagonist, reducing gastrointestinal motility and secretory activity. In the Indian context, it is widely prescribed for abdominal colic and spasms, often in combination with other agents like simethicone.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: 1 to 2 hours. Intramuscular: 20 to 30 minutes. | Approximately 4 to 6 hours after oral administration. | Oral bioavailability is approximately 67-73%. |
2. Mechanism of Action
Dicyclomine is a competitive antagonist at muscarinic (M1, M2, M3) acetylcholine receptors. By blocking the action of acetylcholine on these receptors in smooth muscle, it produces a direct antispasmodic effect on the gastrointestinal tract, reducing tone, amplitude, and frequency of peristaltic contractions. It may also have a direct relaxant effect on smooth muscle via a non-anticholinergic mechanism, though this is less prominent.
3. Indications & Uses
- Symptomatic treatment of Irritable Bowel Syndrome (IBS)
- Treatment of functional gastrointestinal disorders associated with smooth muscle spasm (intestinal colic)
4. Dosage & Administration
Adult Dosage: Initial: 20 mg four times daily (before meals and at bedtime). May increase to 40 mg four times daily if tolerated and required. Usual maintenance: 20 mg three to four times daily. Maximum daily dose: 160 mg.
Administration: Take orally with a full glass of water, 30 minutes to 1 hour before meals and at bedtime. Do not crush or chew sustained-release formulations. The tablet can be taken with or without food, but taking before meals may provide better symptom relief for IBS.
5. Side Effects
Common side effects may include:
- Dry mouth (xerostomia)
- Blurred vision
- Dizziness
- Drowsiness/sedation
- Nausea
- Constipation
- Lightheadedness
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other Anticholinergics (e.g., Atropine, Oxybutynin, TCAs, Antihistamines) | Additive anticholinergic effects (dry mouth, constipation, urinary retention, confusion, tachycardia). | Major |
| Potassium Chloride (wax-matrix formulations) | Increased risk of GI mucosal lesions/ulceration due to reduced motility. | Moderate |
| Metoclopramide | Pharmacological antagonism; dicyclomine reduces GI motility, counteracting metoclopramide's prokinetic effect. | Moderate |
| Digoxin | Increased bioavailability of digoxin due to reduced GI motility, potentially leading to toxicity. | Moderate |
| Amantadine | Enhanced anticholinergic side effects and risk of psychosis. | Moderate |
| Benzodiazepines (e.g., Lorazepam), Opioids, Alcohol | Additive CNS depression (drowsiness, dizziness, impaired coordination). | Moderate |
| Antacids (containing Aluminium/Magnesium) | May reduce absorption of dicyclomine. Administer at least 1-2 hours apart. | Minor |
7. Patient Counselling
- Do take the medication exactly as prescribed, usually before meals.
- Do inform your doctor about all other medications, including OTC drugs and herbal supplements.
- Do maintain adequate fluid intake to prevent constipation.
- Do use sugar-free gum or candies to relieve dry mouth.
- Don't drive or operate heavy machinery until you know how the medicine affects you.
- Don't take antacids within 1-2 hours of taking dicyclomine.
- Don't stop the medication abruptly if taken for a long period; consult your doctor.
- Don't take a double dose to make up for a missed one.
8. Toxicology & Storage
Overdose: Symptoms are extensions of its pharmacologic effects: CNS (restlessness, confusion, hallucinations, psychosis, seizures, respiratory failure), cardiovascular (tachycardia, palpitations, hypotension, circulatory collapse), peripheral anticholinergic (blurred vision, dry mouth, hyperthermia, flushed skin, urinary retention, ileus).
Storage: Store at room temperature (15-30°C), protected from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.