Hyoscine Injection Dose
For adults, hyoscine (scopolamine) is administered intravenously or intramuscularly at 0.2-0.4 mg (200-400 mcg) as a single dose, with a maximum of 20 mg, though typical clinical use rarely exceeds 0.4-0.6 mg per dose.
Adult Dosing by Route and Indication
Intravenous Administration
- Standard dose: 0.2-0.4 mg IV as a single bolus 1
- Low-dose alternative: 5 mg (0.005 mg/kg) has been shown equally effective with fewer cardiovascular side effects compared to 10 mg, particularly in elderly patients and men 2
- Pharmacokinetics: IV administration produces rapid onset with peak effect within 5 minutes and elimination half-life of approximately 1.85 hours 1
Intramuscular Administration
- Standard dose: 0.2 mg IM for motion sickness prevention 3
- Alternative dosing: 0.01 mg/kg IM (approximately 0.6-0.8 mg for average adult) 1
- Onset: Peak plasma levels occur at 10 minutes post-injection 1
- Duration: Approximately 4 hours of antiemetic effect 3
Pediatric Dosing
For children, hyoscine 0.2 mg/kg IM has been used as premedication, though this is not FDA-approved for pediatric use 4. The drug label specifically notes scopolamine transdermal system is not approved for pediatric patients 5.
Clinical Context and Practical Considerations
Dose Selection Strategy
Start with lower doses (0.2 mg or 5 mg) in:
- Elderly patients (increased sensitivity to neuropsychiatric effects) 5
- Patients with cardiovascular disease (risk of tachycardia and hypotension) 2
- First-time users (assess tolerance)
Use standard doses (0.4 mg or 10 mg) in:
- Younger, healthy adults requiring maximum antiemetic effect
- Patients with prior tolerance to anticholinergics
Route-Specific Efficacy
The intramuscular route is 8 times more potent than oral administration 3, making it highly effective when gastric motility is compromised (e.g., during active motion sickness or post-operative nausea).
Critical Safety Warnings
Contraindications
- Absolute: Angle-closure glaucoma 5
- Relative: History of psychosis, seizures, or cognitive impairment 5
Monitoring Requirements
- Cardiovascular: Heart rate and blood pressure during and after administration, especially with doses ≥10 mg 2
- Neuropsychiatric: Monitor for confusion, hallucinations, agitation, or acute toxic psychosis 5, 6
- Intraocular pressure: In patients with open-angle glaucoma 5
Common Pitfalls
- Overdosing elderly patients: Use 50% dose reduction (0.2 mg maximum) due to increased sensitivity 5
- Rapid IV push: Can precipitate acute anticholinergic syndrome; administer slowly over 2-3 minutes 1
- Combining with other anticholinergics: Additive effects increase risk of delirium and urinary retention 6
- Missing diagnosis: Standard urine toxicology does NOT detect scopolamine; requires GC-MS if toxicity suspected 6
Duration of Action
- IV: 3-4 hours clinical effect 1
- IM: 4 hours antiemetic effect, up to 12 hours with promethazine combination 3
- Antisecretory effects: Persist longer than central effects across all routes 1
Comparison with Alternative Formulations
The transdermal system delivers 1 mg over 72 hours (approximately 0.014 mg/hour), which is substantially lower than injectable doses but provides sustained effect 5. Injectable routes are preferred for acute situations requiring rapid onset.