BENTYL PRESERVATIVE FREE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BENTYL PRESERVATIVE FREE (BENTYL PRESERVATIVE FREE).
Dicyclomine is a muscarinic acetylcholine receptor antagonist (anticholinergic) that inhibits the action of acetylcholine on structures innervated by postganglionic parasympathetic nerves. It reduces smooth muscle spasm in the gastrointestinal tract by blocking M1, M2, and M3 receptors, with a predominant effect on M3 receptors in the gut.
| Metabolism | Dicyclomine is metabolized in the liver via N-demethylation and ester hydrolysis, primarily by CYP3A4 and possibly other CYP enzymes. |
| Excretion | Renal: ~50% (mostly as metabolites), Biliary/Fecal: ~40% (as unchanged drug and metabolites), minor via enterohepatic circulation. |
| Half-life | Terminal elimination half-life: 1.9–3.3 hours (in healthy adults). Clinically, short half-life necessitates frequent dosing for sustained effect. |
| Protein binding | ~90% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | 2.6–3.5 L/kg, indicating extensive tissue distribution (beyond total body water). |
| Bioavailability | Oral: ~5–10% (low due to extensive first-pass metabolism). Intramuscular: ~65–80%. Intravenous: 100%. |
| Onset of Action | Oral: 1–2 hours. Intramuscular: 10–30 minutes. Intravenous: 5–10 minutes. |
| Duration of Action | Oral: 4–6 hours. Intramuscular: 3–4 hours. Intravenous: 2–3 hours. Duration may be shorter in certain patient populations (e.g., elderly, hepatic dysfunction). |
| Molecular Weight | 309.45 |
20 mg orally three times daily; may increase to 40 mg three times daily if tolerated.
| Dosage form | INJECTABLE |
| Renal impairment | No dosage adjustment required for any degree of renal impairment. |
| Liver impairment | Use with caution; no specific guidelines. Consider dose reduction in severe hepatic impairment (Child-Pugh Class C). |
| Pediatric use | Children 2–12 years: 5 mg orally three times daily; children >12 years: same as adult. |
| Geriatric use | Initiate at lower dose (10 mg orally three times daily) due to increased sensitivity to anticholinergic effects; titrate cautiously. |
| 1st trimester | Teratogenic effects: Dicyclomine is not recommended in the first trimester due to potential teratogenic risk. Animal studies have shown adverse effects, but human data are limited. Use only if clearly needed. |
| 2nd trimester | Dicyclomine may be used with caution in the second trimester if the benefit outweighs risk. Monitor for anticholinergic effects. |
| 3rd trimester | Avoid in third trimester due to potential premature labor or neonatal anticholinergic effects (e.g., ileus, respiratory depression). |
Clinical note
Comprehensive clinical and safety monograph for BENTYL PRESERVATIVE FREE (BENTYL PRESERVATIVE FREE).
| Placental transfer | Dicyclomine crosses the placenta based on animal data and lipophilic properties. Human data are limited but suggest placental transfer. |
| Breastfeeding | Dicyclomine is excreted into breast milk in small amounts. Use caution due to potential anticholinergic effects in the infant, including constipation, drowsiness, or reduced feeding. The manufacturer does not recommend breastfeeding while taking this drug. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to dicyclomine or any component of the formulationGlaucoma (angle-closure or undiagnosed narrow-angle)Obstructive uropathy (e.g., prostatic hypertrophy with urinary retention)Obstructive gastrointestinal disease (e.g., ileus, pyloroduodenal stenosis)Severe ulcerative colitisMyasthenia gravisReflux esophagitisUnstable cardiovascular status in acute hemorrhageChildren under 6 months of age (injectable form: under 2 years)
| Precautions | Anticholinergic effects: may cause confusion, hallucinations, drowsiness, blurred vision, and heat stroke in hot environments, Risk of severe anticholinergic effects in elderly patients (Beers Criteria), Use with caution in patients with prostate hypertrophy, urinary retention, glaucoma, or myasthenia gravis, May decrease GI motility leading to paralytic ileus, Not recommended for infant colic due to risk of seizures and apneic episodes, Use with caution in patients with hepatic or renal impairment |
| Food/Dietary | No specific food interactions. Avoid alcohol (increase CNS depression). High-fat meals may delay absorption; take on empty stomach for consistent effect. Grapefruit juice has no reported interaction. Maintain adequate hydration to mitigate constipation. |
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| Lactation Rating | L4 - Possibly Hazardous |
| Teratogenic Risk | In first trimester, no adequate studies; risk cannot be excluded. Second and third trimesters: no documented teratogenicity; may cause decreased gastric motility and potential tachycardia in fetus if high doses used. |
| Fetal Monitoring | Monitor maternal heart rate, blood pressure, and signs of anticholinergic toxicity (dry mouth, blurred vision, urinary retention). Fetal monitoring recommended if signs of maternal toxicity. |
| Fertility Effects | No specific data on human fertility impairment. Animal studies showed no adverse effects on fertility. |
| Clinical Pearls | BENTYL (dicyclomine) is an anticholinergic/antispasmodic used for irritable bowel syndrome. Preservative-free formulation reduces risk of allergic reactions in sensitive patients. Onset 1-2 hours; avoid in patients with glaucoma, myasthenia gravis, obstructive uropathy, or gastrointestinal obstruction. Use with caution in elderly due to increased risk of confusion, falls, and anticholinergic side effects. May exacerbate gastroesophageal reflux disease (GERD) by decreasing lower esophageal sphincter tone. Monitor for constipation, urinary retention, and heat stroke in hot environments. Do not withdraw abruptly after prolonged use. |
| Patient Advice | Take exactly as prescribed, usually 30 to 60 minutes before meals and at bedtime. · Do not crush or chew extended-release capsules. · Avoid alcohol and other CNS depressants as they may increase drowsiness. · May cause dry mouth, blurred vision, or dizziness; avoid driving until effects are known. · Report severe constipation, difficulty urinating, or eye pain immediately. · Use caution in hot weather or during exercise; may decrease sweating and increase risk of heat stroke. · Inform all healthcare providers about use, especially dentists or surgeons, due to potential interactions with anesthesia. · Do not stop suddenly without consulting physician, as withdrawal may cause rebound symptoms. |