What is the starting dose for Levsin (hyoscyamine)?

Starting Dose for Levsin (Hyoscyamine)

The starting dose of Levsin (hyoscyamine sulfate) varies by age and formulation: for adults and children ≥12 years, start with 1-2 mL of oral drops or 1-2 teaspoonfuls of elixir every 4 hours as needed; for children 2 to <12 years, use 0.25-1 mL of drops or weight-based elixir dosing; and for infants <2 years, use weight-based drop dosing starting as low as 4 drops (0.01 mg) for a 3.4 kg infant. 1

Adult and Adolescent Dosing (≥12 years)

• Oral drops: Start with 1-2 mL every 4 hours or as needed, not exceeding 12 mL in 24 hours 1
• Elixir: Start with 1-2 teaspoonfuls (5-10 mL) every 4 hours or as needed, not exceeding 12 teaspoonfuls in 24 hours 1
• Intravenous: 0.5 mg IV has been studied for colonoscopy premedication, though this resulted in a 27% incidence of sinus tachycardia 2
• Sublingual spray: 0.25 mg sublingual spray 15-30 minutes before procedures has demonstrated efficacy in reducing procedural difficulty 3

Pediatric Dosing (2 to <12 years)

• Oral drops: 0.25-1 mL every 4 hours or as needed, not exceeding 6 mL in 24 hours 1
• Elixir (weight-based):
  • 10 kg (22 lb): 1/4 teaspoon (1.25 mL) 1
  • 20 kg (44 lb): 1/2 teaspoon (2.5 mL) 1
  • 40 kg (88 lb): 3/4 teaspoon (3.75 mL) 1
  • 50 kg (110 lb): 1 teaspoon (5 mL) 1
• Maximum: 6 teaspoonfuls in 24 hours 1

Infant Dosing (<2 years)

Weight-based drop dosing repeated every 4 hours as needed 1:

• 3.4 kg (7.5 lb): 4 drops (0.01 mg), maximum 24 drops/24 hours 1
• 5 kg (11 lb): 5 drops (0.0175 mg), maximum 30 drops/24 hours 1
• 7 kg (15 lb): 6 drops, maximum 36 drops/24 hours 1
• 10 kg (22 lb): 8 drops, maximum 48 drops/24 hours 1

Important Clinical Considerations

• Onset and duration: Hyoscyamine is rapidly absorbed through the GI tract, reaches peak effects in 2-2.5 hours, and is excreted in urine within 24 hours 4
• Measurement precision: Dosage must be measured very carefully, particularly in pediatric patients, using the calibrated dropper provided with oral drops 1
• Cardiovascular monitoring: When used intravenously, particularly at the 0.5 mg dose studied for procedures, monitor for sinus tachycardia which occurred in 27% of patients, with two cases being extremely rapid 2
• Anticholinergic effects: As an anticholinergic agent, hyoscyamine reduces duodenal motility and is used as adjunct therapy in peptic ulcer disease and irritable bowel syndrome 5, 4

Procedural Use Context

• For colonoscopy premedication, sublingual spray (0.25 mg) administered 15-30 minutes before the procedure significantly reduced procedural difficulty scores and colonic motility scores compared to placebo 3
• IV hyoscyamine (0.5 mg) shortened cecal intubation time (median 9.2 vs 12.9 minutes) and total procedure time, though the high incidence of tachycardia requires caution 2