METHSCOPOLAMINE BROMIDE
Clinical safety rating: safe
Other anticholinergic drugs can have additive effects Can cause drowsiness and confusion.
Antimuscarinic agent that competitively antagonizes acetylcholine at muscarinic receptors, inhibiting gastrointestinal motility and secretions.
| Metabolism | Primarily hepatic via hydrolysis and conjugation. |
| Excretion | Primarily renal excretion of unchanged drug and metabolites; approximately 60-70% excreted in urine within 24 hours, with the remainder eliminated in feces via biliary excretion. |
| Half-life | Terminal elimination half-life is approximately 1.5-2 hours in adults; clinical context: requires frequent dosing (every 4-6 hours) to maintain therapeutic effect. |
| Protein binding | Approximately 30-50% bound primarily to albumin; low binding suggests minimal displacement interactions. |
| Volume of Distribution | Vd approximately 2-4 L/kg; indicates extensive distribution into tissues, including the central nervous system (quaternary ammonium structure limits CNS penetration). |
| Bioavailability | Oral: 10-25% due to poor absorption and first-pass metabolism; Intramuscular: approximately 100%. |
| Onset of Action | Oral: 30-60 minutes; Intramuscular: 10-20 minutes; Intravenous: within 2-5 minutes. |
| Duration of Action | Oral: 4-6 hours; Parenteral: 3-4 hours; clinical notes: shorter duration with IV administration due to rapid redistribution. |
| Molecular Weight | 398.3 |
2.5 to 5 mg orally three times daily and at bedtime; or 0.25 to 1 mg subcutaneously or intramuscularly every 6 to 8 hours.
| Dosage form | TABLET |
| Renal impairment | No specific guidelines; use with caution in severe renal impairment (CrCl <30 mL/min) due to potential for anticholinergic toxicity. |
| Liver impairment | No specific guidelines; use with caution in severe hepatic impairment (Child-Pugh class C) due to reduced metabolism. |
| Pediatric use | Safety and efficacy not established in pediatric patients; no standard weight-based dosing available. |
| Geriatric use | Initiate at lower end of dosing range due to increased sensitivity to anticholinergic effects (e.g., confusion, constipation, urinary retention). |
| 1st trimester | Avoid due to anticholinergic effects; animal studies show risk, no adequate human studies. |
| 2nd trimester | Avoid unless clearly needed; may cause fetal tachycardia or impair GI motility. |
| 3rd trimester | Avoid near term; may interfere with neonatal adaptation (e.g., respiratory depression, feeding difficulties). |
Clinical note
Other anticholinergic drugs can have additive effects Can cause drowsiness and confusion.
| FDA category | Animal |
| Placental transfer | Crosses placenta; degree not well quantified. Quaternary ammonium structure limits transfer, but detectable in fetal circulation. |
| Breastfeeding |
■ FDA Black Box Warning
None.
| Common Effects | nausea |
| Serious Effects |
Glaucoma (narrow-angle)Obstructive uropathy (e.g., bladder neck obstruction due to prostatic hypertrophy)Gastrointestinal obstruction (e.g., pyloric stenosis, ileus)Tachycardia or thyrotoxicosisMyasthenia gravis (unless used to reduce side effects of anticholinesterases)Hypersensitivity to methscopolamine or belladonna alkaloids
| Precautions | May cause blurred vision (avoid driving or operating machinery until effects resolve), Use caution in patients with glaucoma, prostatic hyperplasia, or urinary retention, May precipitate acute angle-closure glaucoma, Use in high environmental temperatures may cause heat stroke, Elderly patients may be more sensitive to anticholinergic effects |
| Food/Dietary |
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| Excreted in small amounts into breast milk; unlikely to affect infant due to poor oral bioavailability, but caution with high doses. Monitor infant for anticholinergic effects. |
| Lactation Rating | L3 (Moderately Safe) - limited data suggest minimal risk if used at usual doses. |
| Teratogenic Risk | Methscopolamine bromide is an anticholinergic agent. Data in pregnant women are limited. Animal studies have not been reported. Anticholinergics as a class are not strongly associated with major malformations. Potential risks include transient neonatal anticholinergic effects (e.g., ileus, tachycardia) if used near term. Use only if clearly needed. |
| Fetal Monitoring | Monitor maternal heart rate and blood pressure due to anticholinergic effects. In the fetus, assess heart rate variability; tachycardia may occur. In neonates, observe for transient anticholinergic effects (e.g., decreased gastrointestinal motility, urinary retention). |
| Fertility Effects | No specific human data on fertility. Anticholinergic agents may theoretically interfere with ovulation via hypothalamic-pituitary effects, but clinical significance is unclear. No known impact on spermatogenesis. |
| No significant food interactions. Avoid excessive alcohol intake as it may increase CNS depression. Absorption may be decreased with high-fat meals; take on an empty stomach if possible. |
| Clinical Pearls | Methscopolamine bromide is a quaternary ammonium anticholinergic that does not cross the blood-brain barrier significantly, minimizing CNS side effects. It is used adjunctively for peptic ulcer disease to reduce gastric acid secretion. Onset of action is 30-60 minutes; avoid concurrent use with other anticholinergics. Contraindicated in glaucoma, obstructive uropathy, GI obstruction, myasthenia gravis, and severe ulcerative colitis. Monitor for anticholinergic toxicity (hyperthermia, ileus, urinary retention). |
| Patient Advice | Take this medication exactly as prescribed, typically 30-60 minutes before meals and at bedtime. · Do not crush or chew extended-release tablets. · Avoid alcohol and activities requiring mental alertness until effects are known (drowsiness or blurred vision may occur). · Report symptoms of eye pain, difficulty urinating, or severe constipation promptly. · Do not take over-the-counter anticholinergic medications (e.g., diphenhydramine) without consulting your doctor. |