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 |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other anticholinergic drugs can have additive effects Contraindicated in patients with glaucoma or severe ulcerative colitis.
| Breastfeeding | Not recommended during breastfeeding. M/P ratio not established. Dicyclomine may suppress lactation and has been associated with infant apnea (notably in combination with doxylamine/pyridoxine). Excretion into breast milk likely but clinical significance unknown. |
| 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. |
■ FDA Black Box Warning
Not applicable.
| Common Effects | Dry mouth |
| Serious Effects |
["Obstructive uropathy","Obstructive gastrointestinal tract disease","Severe ulcerative colitis","Glaucoma","Myasthenia gravis","Hypersensitivity to dicyclomine"]
| Precautions | May cause anticholinergic effects (dry mouth, blurred vision, urinary retention); caution in patients with glaucoma, myasthenia gravis, or prostatic hypertrophy. |
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| 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. |