What is the recommended dosage and usage of hyoscyamine?

Hyoscyamine Dosage and Usage

The maximum daily dose of hyoscyamine is 1.5 mg for adults, administered as 0.125 mg orally/sublingually every 4 hours as needed, with dosing adjusted based on patient age, weight, and clinical indication. 1, 2

Standard Adult Dosing

For adults and pediatric patients ≥12 years:

• Oral drops: 1-2 mL every 4 hours as needed (maximum 12 mL/24 hours) 2
• Elixir: 1-2 teaspoonfuls every 4 hours as needed (maximum 12 teaspoonfuls/24 hours) 2
• Tablets/sublingual: 0.125 mg every 4 hours as needed (maximum 1.5 mg/24 hours) 1

Pediatric Dosing

For children 2 to <12 years:

• Weight-based dosing is essential, with maximum daily limits strictly observed 2
• Oral drops: 0.25-1 mL every 4 hours (maximum 6 mL/24 hours) 2
• Elixir dosing by weight:
  • 10 kg (22 lb): 1.25 mL (1/4 teaspoon)
  • 20 kg (44 lb): 2.5 mL (1/2 teaspoon)
  • 40 kg (88 lb): 3.75 mL (3/4 teaspoon)
  • 50 kg (110 lb): 5 mL (1 teaspoon)
  • Maximum 6 teaspoonfuls/24 hours 2

For infants <2 years:

• Dosing is strictly weight-based using oral drops 2
• 3.4 kg (7.5 lb): 4 drops every 4 hours (maximum 24 drops/24 hours)
• 5 kg (11 lb): 5 drops every 4 hours (maximum 30 drops/24 hours)
• 7 kg (15 lb): 6 drops every 4 hours (maximum 36 drops/24 hours)
• 10 kg (22 lb): 8 drops every 4 hours (maximum 48 drops/24 hours) 2

Clinical Applications

Palliative Care - Excessive Secretions:

• Hyoscyamine 0.125 mg PO/ODT/SL every 4 hours as needed is a second-line option when glycopyrrolate is insufficient 1
• Alternative routes (rectal, transdermal, subcutaneous, IV) may be used when oral administration is not feasible 1

Malignant Bowel Obstruction:

• Used as an anticholinergic agent when other measures fail, alongside scopolamine and glycopyrrolate 1
• Administered via alternative routes when oral intake is compromised 1

Chronic Abdominal Pain:

• Can be used as an antispasmodic in hypermobile Ehlers-Danlos syndrome and related conditions 1

Safety Monitoring and Contraindications

Monitor for anticholinergic side effects:

• Dry mouth, urinary retention, constipation, and blurred vision are common 1
• In elderly or post-stroke patients, hyoscyamine may cause more CNS effects compared to glycopyrrolate, which does not cross the blood-brain barrier 1

Use with extreme caution or avoid in:

• Cardiac patients with tachycardia, angina, or cardiac failure 3
• Prostatic hypertrophy with urinary retention 3
• Glaucoma patients should be counseled to seek emergency care if experiencing eye pain, redness, decreased vision, nausea, vomiting, or headache after administration 3

Clinical Considerations

Gastroesophageal reflux disease:

• Hyoscyamine and related anticholinergics increase esophageal acid reflux episodes and are not recommended for GERD treatment 4

Endoscopic procedures:

• Evidence does not support routine use during colonoscopy or gastroscopy 3
• May be considered during ERCP, though glucagon remains standard 3, 5

Cost and administration:

• Oral hyoscyamine is considerably less expensive than IV glucagon for antispasmodic effects 6
• Sublingual administration provides rapid onset when needed 5