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# Dicyclomine hydrochloride
## Overview
Dicyclomine is an antispasmodic and anticholinergic agent that acts by direct relaxation of smooth muscle in the gastrointestinal (GI) tract and through acetylcholine blockade at muscarinic receptors.
## Primary Indications
Functional bowel/irritable bowel syndrome (IBS).
## Adult Dosing
* **Initial:** 20 mg PO four times daily.
* **Titration:** After one week, may increase to 40 mg PO four times daily if tolerated.
* **Discontinuation:** If efficacy is not achieved at 80 mg/day after two weeks, discontinue therapy.
* **Intramuscular (IM):** 20 mg every 4 to 6 hours. (Not for IV use).
## Pediatric Dosing
* **Safety/Efficacy:** Not established for pediatric populations. Use is generally discouraged due to clinical reports of serious respiratory and neurologic adverse events in infants < 6 months.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No formal guidelines exist for dose adjustment; use with extreme caution in patients with hepatic or renal impairment due to the risk of anticholinergic toxicity and impaired drug clearance.
* **Geriatric:** Avoid in patients ≥ 65 years (Beers Criteria) due to high risk of adverse CNS effects (confusion, delirium) and urinary retention.
## Contraindications
* Hypersensitivity to the drug.
* Infants < 6 months.
* Unstable cardiovascular status in acute hemorrhage.
* Myasthenia gravis.
* Obstructive GI disease (e.g., pyloroduodenal stenosis, achalasia, paralytic ileus).
* Severe ulcerative colitis or toxic megacolon.
* Glaucoma.
* Obstructive uropathy.
## Adverse Effects
* **Common:** Dry mouth, dizziness, blurred vision, nausea, nervousness, somnolence, and constipation.
* **Serious:** Tachycardia, urinary retention, heatstroke (due to suppressed sweating), confusion/hallucinations (secondary to central anticholinergic syndrome), and anaphylaxis.
## Key Drug Interactions
* **Other Anticholinergics:** Additive toxicity (e.g., antihistamines, tricyclic antidepressants, antipsychotics).
* **Potassium Chloride (Solid dosage forms):** Increased risk of GI mucosal lesions due to prolonged transit time.
* **Digoxin:** Increased serum concentrations possible due to decreased GI motility.
## Monitoring
* Monitor for signs of anticholinergic toxicity (tachycardia, urinary retention, severe constipation, mental status changes).
* Monitor for GI symptom relief.
## Clinical Pearls
* **Administration:** Take before meals.
* **Heat Sensitivity:** Caution patients that drug-induced hypohidrosis increases the risk of heatstroke during exercise or hot weather.
* **IV Usage:** Dicyclomine must **never** be administered intravenously; it is intended for oral or intramuscular use only.
* **CNS Effects:** Dicyclomine crosses the blood-brain barrier; advise patients to avoid tasks requiring mental alertness until individual response is known.
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**Educational Disclaimer:** This information is for educational purposes only. Always verify dosing, contraindications, and drug interactions against current institutional protocols and the manufacturer's official FDA-approved prescribing information (package insert) before prescribing or administering medication.
