Overview
Hyoscine butylbromide is an antispasmodic medication that acts as a competitive antagonist at muscarinic acetylcholine receptors, primarily used to relieve smooth muscle spasms in the gastrointestinal, biliary, and genitourinary tracts. It has limited ability to cross the blood-brain barrier, resulting in fewer central nervous system effects compared to other anticholinergics.
Mechanism of Action
Competitive antagonist at muscarinic acetylcholine receptors (M1, M2, M3 subtypes) in smooth muscle of gastrointestinal, biliary, and genitourinary tracts. Blocks acetylcholine-mediated smooth muscle contraction, reducing spasms and motility without significantly affecting gastric acid secretion.
Indications
- Symptomatic relief of abdominal cramps and pain associated with irritable bowel syndrome
- Renal and biliary colic
- Dysmenorrhea
- Smooth muscle spasm in diagnostic procedures (e.g., endoscopy)
Dosage
Adults: 10-20 mg orally 3-4 times daily as needed. Maximum daily dose: 80 mg. For acute spasms: 20 mg intramuscularly or intravenously, may repeat after 30 minutes if needed. Children (6+ years): 10 mg orally 3 times daily.
Contraindications
- Hypersensitivity to hyoscine butylbromide or anticholinergics
- Myasthenia gravis
- Glaucoma (angle-closure)
- Prostatic hypertrophy with urinary retention
- Mechanical gastrointestinal obstruction
- Paralytic ileus
- Severe ulcerative colitis
- Tachyarrhythmias
Side Effects
- Dry mouth
- Blurred vision
- Tachycardia
- Dizziness
- Drowsiness
- Constipation
- Difficulty urinating
- Allergic reactions (rash, urticaria)
- Nausea
- Flushing
Interactions
- Enhanced anticholinergic effects with other anticholinergics (tricyclic antidepressants, antihistamines, phenothiazines)
- Reduced absorption with antacids (separate administration by 2 hours)
- May antagonize effects of prokinetic agents (metoclopramide, domperidone)
- Possible additive sedative effects with CNS depressants
- May increase heart rate when combined with sympathomimetics