Hyoscyamine (Scopolamine) Dosing for Nausea/Vomiting and Motion Sickness
For motion sickness prevention, apply one scopolamine transdermal patch (1.5 mg) to the hairless area behind one ear at least 4 hours before antiemetic effect is required, effective for up to 3 days. 1
Motion Sickness Prevention
- Apply the transdermal patch at least 4-8 hours before travel to achieve protective plasma concentrations (approximately 50 pg/mL), with steady-state levels of ~100 pg/mL reached 8-12 hours after application 1, 2
- Each patch delivers 1 mg of scopolamine over 72 hours at a constant rate of approximately 5 mcg/hour 1
- For faster protection when needed within 1 hour, combine the patch with oral scopolamine 0.3-0.6 mg 2
- If therapy beyond 3 days is required, remove the first patch and apply a new one behind the opposite ear 1
Postoperative Nausea and Vomiting (PONV)
- For surgeries other than cesarean section, apply one patch behind the ear the evening before surgery and remove 24 hours following surgery 1
- The transdermal formulation reduces postoperative nausea and vomiting with no significant differences in dizziness, drowsiness, fatigue, blurred vision, or dry mouth compared to placebo 3
Breakthrough Nausea/Vomiting Treatment
When scopolamine is used as a rescue agent for breakthrough symptoms:
- Scopolamine patch: 1 patch applied every 72 hours 3
- Oral/sublingual hyoscyamine: 0.125 mg every 4 hours as needed (maximum 1.5 mg/day) 4
- For increased oral secretions in palliative care settings, scopolamine can be dosed topically at 1.5-3 mg every 72 hours 3
Refractory Gastroparesis
- Scopolamine 1.5 mg patch applied every 3 days is listed as an off-label treatment option for nausea and vomiting in medically refractory gastroparesis, though it lacks supporting clinical studies 3
Critical Administration Instructions
- Only wear one transdermal patch at a time; do not cut the patch 1
- Wash hands thoroughly with soap and water immediately after application to prevent finger-to-eye contamination, which can cause mydriasis and blurred vision 1, 2
- Avoid touching or applying pressure to the patch once applied 1
- Upon removal, fold the used patch in half with sticky sides together and discard safely to prevent accidental contact or ingestion 1
Common Pitfalls and Adverse Effects
Dry mouth occurs in 50-60% of patients, drowsiness in up to 20%, and allergic contact dermatitis in 10% 2
- Blurred vision and impaired ocular accommodation are common; hypermetropic (farsighted) individuals are at particular risk, especially with repeated applications 5, 2
- Low-dose pyridostigmine can prevent cycloplegia but not mydriasis if visual symptoms become problematic 2
- 20-30% of patients fail to attain protective plasma concentrations (50 pg/mL), which may explain treatment failures 2
- CNS effects include impaired memory for new information, reduced attention, and decreased alertness, particularly with prolonged or repeated use 5
- Withdrawal symptoms may occur 24 hours or more after patch removal 1
Contraindications and Warnings
- Absolutely contraindicated in angle-closure glaucoma 1
- Monitor patients with open-angle glaucoma for increased intraocular pressure and adjust glaucoma therapy as needed 1
- Avoid in patients with severe preeclampsia due to risk of eclamptic seizures 1
- Use caution in patients with intestinal obstruction, pyloric obstruction, or impeded urine flow 1
- May cause psychiatric and cognitive effects including toxic psychosis, particularly in elderly and pediatric patients 1, 2
- Discontinue if difficulty urinating develops 1
Comparative Efficacy
- Scopolamine is the most effective single agent for preventing motion sickness, reducing incidence and severity by 60-80% compared to placebo 6, 2
- The transdermal formulation is superior to oral meclizine or cinnarizine, similar to oral scopolamine 0.6 mg or promethazine plus ephedrine, and equivalent or superior to dimenhydrinate 2
- Produces approximately half the drowsiness of oral dimenhydrinate or cinnarizine 2