DICYCLOMINE HYDROCHLORIDE
Clinical safety rating: safe
Animal studies have demonstrated safety
Competitive antagonist of muscarinic acetylcholine receptors, inhibiting parasympathetic nerve impulses in the gastrointestinal tract, leading to smooth muscle relaxation.
| Metabolism | Hepatic metabolism via demethylation and hydroxylation; CYP450 enzymes not well characterized. |
| Excretion | Renal (∼79.5% as unchanged drug and metabolites) with minor biliary/fecal elimination (∼8-10%) |
| Half-life | 1.8 to 2.5 hours (terminal half-life, shorter in younger patients) |
| Protein binding | ~90% bound to serum albumin |
| Volume of Distribution | 4.27 L/kg (large Vd indicating extensive tissue distribution) |
| Bioavailability | Oral: ~60-70% (first-pass metabolism); IM: 100% |
| Onset of Action | Oral: <30 minutes; Intramuscular: <15 minutes |
| Duration of Action | Oral: 4-6 hours; Intramuscular: 3-4 hours |
| Molecular Weight | 345.95 |
10-20 mg orally 3-4 times daily
| Dosage form | CAPSULE |
| Renal impairment | No specific adjustment recommended; use caution in severe impairment |
| Liver impairment | No specific adjustment recommended; use caution in severe impairment |
| Pediatric use | Age <6 months: not recommended; 6 months-2 years: 5-10 mg orally 3-4 times daily; >2 years: 10 mg orally 3-4 times daily |
| Geriatric use | Initiate at 10 mg orally 3-4 times daily; titrate cautiously due to increased anticholinergic sensitivity |
| 1st trimester | Limited human data; animal studies show no risk. Avoid if possible. |
| 2nd trimester | Use only if clearly needed; no known teratogenicity. |
| 3rd trimester | Avoid near term due to potential for anticholinergic effects in neonate (e.g., ileus). |
Clinical note
Other anticholinergic drugs can have additive effects Contraindicated in patients with glaucoma or severe ulcerative colitis.
| Placental transfer | Crosses placenta; evidence from animal studies. |
| Breastfeeding | Excreted into breast milk in small amounts; unlikely to cause adverse effects in infant. Monitor for anticholinergic effects. |
| Lactation Rating |
■ FDA Black Box Warning
Not applicable.
| Common Effects | Dry mouth |
| Serious Effects |
GlaucomaObstructive uropathyObstructive gastrointestinal diseaseSevere ulcerative colitisMyasthenia gravisHypersensitivity to dicyclomine
| Precautions | May cause anticholinergic effects (dry mouth, blurred vision, urinary retention); caution in patients with glaucoma, myasthenia gravis, or prostatic hypertrophy. |
| Food/Dietary | Avoid high-fat meals which may delay absorption. No specific food interactions; however, concurrent use with alcohol or CNS depressants may enhance drowsiness. |
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| Teratogenic Risk | FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, but no adequate human studies in pregnant women. Data is insufficient to confirm safety; use only if clearly needed. No specific teratogenic pattern identified across trimesters. |
| Fetal Monitoring | Monitor maternal heart rate and blood pressure due to anticholinergic effects; observe for signs of toxicity (tachycardia, urinary retention, ileus). Fetal monitoring not routinely required, but may be considered if maternal adverse events occur. |
| Fertility Effects | No documented adverse effects on human fertility. Anticholinergic effects may theoretically impact reproductive function, but clinical data do not indicate significant risk. |
| Clinical Pearls | Dicyclomine is an anticholinergic used for irritable bowel syndrome. Onset of action is 1-2 hours; peak effect at 60-90 min. Monitor for anticholinergic side effects: dry mouth, blurred vision, urinary retention, constipation. Contraindicated in obstructive uropathy, obstructive GI disease, severe ulcerative colitis, myasthenia gravis, glaucoma. Use with caution in hepatic/renal impairment, hyperthyroidism, hypertension, heart failure. May cause drowsiness; advise against driving. |
| Patient Advice | Take exactly as prescribed; do not increase dose or frequency. · May cause dizziness or blurred vision; avoid driving until you know how it affects you. · Avoid alcohol and other CNS depressants. · Drink plenty of fluids to prevent constipation. · Report severe abdominal pain, constipation, difficulty urinating, or vision changes. · Avoid overheating; this drug reduces sweating. |