What is the proper use and dosage of the scopolamine (anticholinergic) patch for preventing nausea and vomiting?

Scopolamine Patch: Proper Use and Dosage

The scopolamine transdermal patch delivers 1 mg of scopolamine over 3 days and should be applied to the hairless area behind one ear at least 4 hours before antiemetic effect is needed for motion sickness, or the evening before surgery for postoperative nausea and vomiting (PONV), with removal 24 hours after surgery. 1

Dosage and Formulation

• Each transdermal patch contains 1.5 mg of scopolamine with a programmed delivery of approximately 1 mg over a 72-hour period at a constant rate of 5 mcg/hour 1, 2
• A priming dose of 140 mcg is incorporated into the adhesive layer to accelerate achievement of steady-state blood levels 2, 3
• Only one patch should be worn at any time; do not cut the patch 1

Application Timing and Technique

For Motion Sickness

• Apply one patch to the hairless area behind one ear at least 4 hours before the antiemetic effect is required 1
• For faster protection (within 1 hour), the patch may be combined with oral scopolamine 0.3-0.6 mg 2
• The patch is most effective 8-12 hours after application 2
• If therapy is needed beyond 3 days, remove the first patch and apply a new one behind the opposite ear 1

For Postoperative Nausea and Vomiting

• Apply one patch the evening before scheduled surgery (for surgeries other than cesarean section) 1
• Remove the patch 24 hours after surgery 1
• The American Society of Anesthesiologists recognizes scopolamine as an effective prophylactic agent for PONV 4

For Chemotherapy-Induced Nausea and Vomiting

• The National Comprehensive Cancer Network recommends the scopolamine patch as a breakthrough treatment option, with application of one patch every 72 hours 5

Application Instructions

• Select a clean, dry, hairless area behind one ear, avoiding cuts or irritated skin 1
• Apply the adhesive surface firmly to the skin with the peach-colored imprinted side facing outward 1
• Wash hands thoroughly with soap and water immediately after application to prevent accidental eye contamination 1
• Avoid touching or applying pressure to the patch once applied, as pressure may cause scopolamine to ooze out at the edges 1

Removal and Disposal

• Upon removal, fold the used patch in half with the sticky sides together 1
• Discard in household trash out of reach of children and pets 1
• Wash both hands and the application site with soap and water after removal 1

Pharmacokinetics and Efficacy

• Protective plasma concentrations (approximately 50 pg/mL) are achieved after 6 hours, with steady-state levels of ~100 pg/mL reached 8-12 hours after application 2
• Meta-analysis demonstrates transdermal scopolamine significantly reduces postoperative nausea (RR=0.59,95% CI 0.48-0.73, P<0.001), vomiting (RR=0.68,95% CI 0.61-0.76, P<0.001), and PONV (RR=0.73,95% CI 0.60-0.88, P=0.001) during the first 24 hours after anesthesia 6, 7
• The patch is effective whether applied the night before surgery (early application) or on the day of surgery (late application) 6

Multimodal Approach

• The American College of Obstetricians and Gynecologists recommends incorporating scopolamine patches as part of a multimodal approach to PONV prevention, as combination regimens are significantly more effective than single agents 8
• Transdermal scopolamine combined with ondansetron provides superior PONV prophylaxis in high-risk patients, particularly reducing nausea between 8-24 hours postoperatively 9

Common Pitfalls and Adverse Effects

Most Common Side Effects

• Dry mouth occurs in 50-60% of patients 2
• Drowsiness affects up to 20% of patients 2
• Visual disturbances (blurred vision, mydriasis) occur more frequently than placebo (RR=3.35,95% CI 1.78-6.32) at 24-48 hours 6

Critical Safety Concerns

• Contraindicated in angle-closure glaucoma; monitor intraocular pressure in open-angle glaucoma patients and discontinue if acute angle-closure symptoms develop 1
• May cause neuropsychiatric effects including confusion, agitation, and rarely toxic psychosis, particularly in elderly patients 1
• Avoid eye contact: accidental finger-to-eye contamination can cause transient cycloplegia and mydriasis 2, 3
• Withdrawal symptoms (dizziness, nausea, vomiting, confusion, muscle weakness) may occur 24 hours or more after patch removal, especially after prolonged use 1

Special Populations

• Avoid use in patients with severe preeclampsia due to risk of eclamptic seizures 1
• Use caution in patients with pyloric obstruction, intestinal obstruction, or impeded urine flow 1
• Readily crosses the placenta; use only when clearly needed in pregnancy 3

Dosing for Refractory Gastroparesis

• For medically refractory gastroparesis, the AGA recommends 1.5 mg patch applied every 3 days as an antiemetic option 4