BENTYL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BENTYL (BENTYL).
Dicyclomine is a muscarinic acetylcholine receptor antagonist that blocks the action of acetylcholine at postganglionic parasympathetic effector sites, reducing gastrointestinal smooth muscle spasms and hypermotility.
| Metabolism | Hepatic, primarily via CYP3A4 and CYP2D6 |
| Excretion | Primarily renal (approximately 60% as unchanged drug and metabolites) and fecal (about 40% via biliary elimination). |
| Half-life | 1.9 to 3 hours (terminal elimination half-life); clinical context: short half-life supports multiple daily dosing for spasm relief. |
| Protein binding | Approximately 90% bound to plasma albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 3.5–7 L/kg (wide distribution, indicating extensive tissue penetration). |
| Bioavailability | Oral: 60–80% (due to first-pass metabolism); Intramuscular: 100%. |
| Onset of Action | Oral: 1–2 hours; Intramuscular: 10–30 minutes; Intravenous: immediate. |
| Duration of Action | Oral: 4–6 hours; Parenteral: 4–8 hours; clinical notes: duration may be extended in hepatic impairment. |
20 mg orally four times daily; may increase to 40 mg four times daily if tolerated. Immediate-release: 20 mg orally every 6 hours. Extended-release: 20 mg orally twice daily.
| Dosage form | CAPSULE |
| Renal impairment | No specific dosing adjustments recommended for renal impairment. Use with caution in severe impairment due to anticholinergic effects. |
| Liver impairment | No specific dosing adjustments recommended for hepatic impairment. Use with caution in severe impairment due to anticholinergic effects. |
| Pediatric use | Children ≥2 years: 10 mg orally three to four times daily; maximum 40 mg/day. Infants and children <2 years: Not recommended due to limited data. |
| Geriatric use | Initiate at low doses (e.g., 10 mg four times daily) and titrate slowly. Avoid use in elderly due to high risk of anticholinergic adverse effects (confusion, constipation, urinary retention). |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BENTYL (BENTYL).
| Breastfeeding | Excreted into breast milk in small amounts (M/P ratio unknown). Use with caution due to potential anticholinergic effects in the infant (e.g., tachycardia, constipation, drowsiness). Monitor infant for these effects. |
| Teratogenic Risk | FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, but no adequate human studies in pregnant women. Use only if clearly needed. First trimester: No evidence of teratogenicity. Second and third trimesters: Potential anticholinergic effects (e.g., ileus, respiratory depression) in the neonate if used near term. |
■ FDA Black Box Warning
None
| Serious Effects |
Obstructive uropathy, obstructive GI tract disease, severe ulcerative colitis, reflux esophagitis, unstable cardiovascular status (e.g., acute myocardial infarction), glaucoma, myasthenia gravis, breastfeeding, hypersensitivity to dicyclomine or any component.
| Precautions | May cause anticholinergic effects (dry mouth, blurred vision, constipation, urinary retention, heat stroke); caution in patients with autonomic neuropathy, hepatic or renal disease, ulcerative colitis, hyperthyroidism, coronary artery disease, congestive heart failure, cardiac arrhythmias, hypertension, hiatal hernia, prostatic hypertrophy, and myasthenia gravis; elderly patients may be more sensitive; do not discontinue abruptly after prolonged use. |
| Food/Dietary | Take with or without food. Grapefruit juice may increase absorption; avoid large quantities. High-fiber foods may reduce absorption; take Bentyl 1 hour before or 2 hours after high-fiber meals. |
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| Fetal Monitoring |
| Monitor maternal blood pressure, heart rate, and signs of anticholinergic toxicity (dry mouth, blurred vision, urinary retention). For fetus, monitor growth and amniotic fluid index. For neonate, observe for anticholinergic effects (e.g., decreased gut motility, respiratory depression) after delivery. |
| Fertility Effects | Animal studies: No evidence of impaired fertility. Human data: Not available; theoretical risk of anticholinergic effects on reproductive function (e.g., impaired ovulation due to altered hormone regulation) but clinical significance unknown. |
| Clinical Pearls | Dicyclomine (Bentyl) is an anticholinergic agent used for irritable bowel syndrome (IBS). It has no effect on gastric acid secretion. Onset of action is 1-2 hours orally. Monitor for anticholinergic side effects: dry mouth, blurred vision, urinary retention. Contraindicated in glaucoma, myasthenia gravis, obstructive uropathy, and gastrointestinal obstruction. Use with caution in elderly due to increased sensitivity. May cause drowsiness or dizziness. |
| Patient Advice | Take exactly as prescribed, usually 30-60 minutes before meals and at bedtime. · Do not drive or operate machinery until you know how this medication affects you, as it may cause dizziness or drowsiness. · Avoid alcohol and other CNS depressants, as they may increase drowsiness. · Report any vision changes, difficulty urinating, or severe constipation. · Swallow capsules whole; do not crush or chew. · Do not stop abruptly without consulting your doctor. |