Appropriate Dosing of Scopolamine for Nausea
The appropriate dosing of scopolamine for nausea is 1.5 mg via transdermal patch, which delivers approximately 1 mg over 3 days at a rate of 5 mcg/hour, or 0.4 mg subcutaneously every 4 hours as needed. 1, 2
Administration Routes and Dosing
Transdermal Administration (Preferred)
- Dosage: 1.5 mg patch delivering 1 mg over 3 days
- Application: Apply to hairless area behind one ear
- Timing: Apply at least 4-6 hours before antiemetic effect is needed
- Duration: Effective for up to 3 days
- For extended use: Remove first patch and apply a new patch behind the opposite ear
Parenteral Administration
- Subcutaneous: 0.4 mg every 4 hours as needed 2
- Intravenous: 0.15-0.25 mg/kg per dose infused over 10 minutes (maximum initial dose: 1 mg) 2
Clinical Applications
Nausea and Vomiting Prevention
- Motion sickness: Transdermal patch applied at least 4 hours before anticipated need
- Post-operative nausea and vomiting: Apply transdermal patch evening before surgery, remove 24 hours after surgery 1
- Palliative care: 0.4 mg subcutaneously every 4 hours as needed for increased oral secretions and associated nausea 2
Pharmacokinetics
Transdermal delivery:
- Includes 140 mcg priming dose to accelerate achievement of steady-state
- Reaches protective plasma concentration (50 pg/mL) after 6 hours
- Achieves steady-state concentration (~100 pg/mL) after 8-12 hours
- Maintains therapeutic levels for 72 hours 3
Oral administration:
- Limited bioavailability (only 2.6% excreted unchanged)
- Peak concentration occurs approximately 30 minutes after administration
- Short half-life limits clinical utility 4
Special Considerations
Combination Therapy
- For rapid onset plus sustained effect: Combine transdermal patch with oral scopolamine (0.3 or 0.6 mg)
- This approach provides therapeutic levels starting at 0.5 hours post-treatment 5
Treatment-Resistant Cases
- Double-dose transdermal scopolamine (two patches) may be considered for patients who fail to respond to a single patch
- Increases plasma concentration (from 81 to 127 pg/mL) without significantly increasing adverse effects 6
Adverse Effects and Monitoring
Common Adverse Effects
- Dry mouth (50-60% of patients)
- Drowsiness (up to 20%)
- Blurred vision and pupil dilation
- Allergic contact dermatitis (10%) 3
Serious Adverse Effects
- Acute angle closure glaucoma (contraindicated in patients with this condition)
- Neuropsychiatric effects including confusion and hallucinations (more common in elderly)
- Urinary retention 1
Monitoring
- Monitor for increased intraocular pressure in patients with open-angle glaucoma
- Watch for new or worsening psychiatric symptoms
- Assess for difficulty urinating, especially in patients with prostatic hypertrophy 1
Contraindications
- Angle closure glaucoma
- Hypersensitivity to scopolamine or belladonna alkaloids
- Caution in severe preeclampsia due to risk of eclamptic seizures 1
Scopolamine is a potent anticholinergic medication that effectively manages nausea through both peripheral antimuscarinic properties and central antiemetic effects. The transdermal delivery system offers significant advantages over oral or parenteral administration by providing sustained therapeutic levels with fewer adverse effects.