Hyosyne - Drug Monograph

Introduction

Hyosyne is a brand name for hyoscine butylbromide, an antispasmodic medication belonging to the class of anticholinergic agents. It is primarily used for the management of gastrointestinal spasms and abdominal pain associated with various conditions. Unlike its close relative hyoscine hydrobromide (scopolamine), hyoscine butylbromide has limited penetration across the blood-brain barrier, resulting in fewer central nervous system effects while maintaining potent peripheral antispasmodic activity.

Mechanism of Action

Hyosyne exerts its therapeutic effects through competitive inhibition of muscarinic acetylcholine receptors in the smooth muscle of the gastrointestinal tract, biliary system, and genitourinary tract. By blocking the action of acetylcholine at these receptor sites, it reduces smooth muscle tone and motility without affecting gastric secretion. The quaternary ammonium structure of hyoscine butylbromide limits its ability to cross the blood-brain barrier, resulting in predominantly peripheral effects with minimal central anticholinergic activity.

Indications

• Symptomatic treatment of abdominal pain and spasms in gastrointestinal disorders including irritable bowel syndrome
• Adjunctive therapy in peptic ulcer disease
• Biliary colic and spasms of the biliary tract
• Spasms of the genitourinary tract (renal colic, dysmenorrhea)
• As an antispasmodic during diagnostic procedures (endoscopic examinations)
• Off-label: Management of sialorrhea in palliative care settings

Dosage and Administration

• Oral: 10-20 mg 3-4 times daily
• Maximum daily dose: 80-100 mg
• Intravenous/Intramuscular: 20-40 mg, repeated as necessary (typically every 6-8 hours)

• Start with lower doses due to increased sensitivity to anticholinergic effects

• Use with caution; consider dose reduction in moderate to severe impairment

• No specific dosage adjustment recommended, but use with caution

• Oral tablets should be taken with water
• Injectable form should be administered slowly intravenously or deep intramuscularly
• May be taken with or without food

Pharmacokinetics

Contraindications

• Known hypersensitivity to hyoscine butylbromide or related compounds
• Myasthenia gravis
• Obstructive gastrointestinal conditions (paralytic ileus, pyloric stenosis)
• Megacolon
• Severe ulcerative colitis
• Glaucoma (particularly narrow-angle)
• Prostatic hypertrophy with urinary retention
• Tachyarrhythmias

Warnings and Precautions

• Use with caution in patients with autonomic neuropathy
• May cause blurred vision - patients should avoid driving or operating machinery if affected
• Risk of urinary retention, particularly in elderly men with prostatic hyperplasia
• May precipitate acute angle-closure glaucoma in susceptible individuals
• Use cautiously in patients with cardiovascular disease due to potential tachycardia
• Avoid in patients with hiatal hernia associated with reflux esophagitis
• May reduce gastrointestinal motility - use cautiously in patients with gastrointestinal obstruction
• Pregnancy Category C: Use only if potential benefit justifies potential risk
• Lactation: Excreted in breast milk; use with caution

Drug Interactions

• Other anticholinergic agents (tricyclic antidepressants, antihistamines, phenothiazines)
• Amantadine
• Disopyramide
• Quinidine

• Metoclopramide and other prokinetic agents
• Acetylcholinesterase inhibitors

• May affect absorption of other orally administered drugs due to altered gastrointestinal motility
• May enhance effects of CNS depressants (although central effects are minimal)

Adverse Effects

• Dry mouth
• Blurred vision
• Tachycardia
• Constipation
• Difficulty urinating
• Reduced sweating

• Dizziness
• Drowsiness
• Nausea
• Skin reactions
• Accommodation disturbances

• Anaphylactic reactions
• Angle-closure glaucoma
• Ileus
• Psychiatric disturbances (more common with high doses)

Monitoring Parameters

• Relief of abdominal pain and spasm symptoms
• Visual acuity and accommodation
• Heart rate and rhythm
• Urinary output and symptoms of retention
• Bowel function and signs of ileus
• Signs of anticholinergic toxicity in elderly patients
• Intraocular pressure in susceptible individuals

Patient Education

• Take as directed; do not exceed prescribed dosage
• May cause blurred vision - avoid driving or hazardous activities if affected
• Maintain adequate hydration to prevent constipation
• Report difficulty urinating, eye pain, or persistent rapid heartbeat
• Inform all healthcare providers about Hyosyne use
• Avoid alcohol as it may enhance certain side effects
• Chew sugar-free gum or suck ice chips to relieve dry mouth
• Store at room temperature away from moisture and heat
• Do not crush or break extended-release formulations

References

1. Tytgat GN. Hyoscine butylbromide: a review of its use in the treatment of abdominal cramping and pain. Drugs. 2007;67(9):1343-57. 2. Pharmaceutical Society of Australia. Australian Medicines Handbook. Adelaide: Australian Medicines Handbook Pty Ltd; 2023. 3. British National Formulary. London: BMJ Group and Pharmaceutical Press; 2023. 4. Müller-Lissner SA et al. Treatment of chronic constipation with hyoscine butylbromide. Aliment Pharmacol Ther. 2010;32(11-12):1353-60. 5. European Medicines Agency. Summary of Product Characteristics: Hyoscine Butylbromide. 2022. 6. American Society of Health-System Pharmacists. AHFS Drug Information. Bethesda, MD: ASHP; 2023. 7. World Health Organization. WHO Model Formulary. Geneva: World Health Organization; 2021.