UWORLD Chapter 74: Motion Sickness

Define nausea.

The uncomfortable, queasy feeling that one may vomit.

What are the three primary neurotransmitter receptors in the chemoreceptor trigger zone (CTZ) that contribute to nausea?

Dopamine (DA), serotonin (5-HT), and acetylcholine (ACh).

Which class of drugs blocks 5-HT3 receptors to reduce nausea?

5-HT3 receptor antagonists (e.g., ondansetron).

What is vertigo?

Dizziness with the sensation that the environment is moving or spinning, typically due to an inner ear condition.

Why are 5-HT3 receptor antagonists not useful for treating vertigo?

They do not affect the inner ear.

What is the recommended drug treatment for vertigo?

Vestibular suppressants, including antihistamines (e.g., meclizine, dimenhydrinate) and benzodiazepines.

What is motion sickness (kinetosis)?

Dizziness and a sensation of being off-balance due to repetitive motions.

What are the two primary drug classes used to treat motion sickness?

Anticholinergics (e.g., scopolamine) and antihistamines (e.g., meclizine).

What non-drug option can be used to treat motion sickness?

A wrist band (e.g., Sea-Band) that presses on an acupuncture point.

What natural supplements can be used to treat motion sickness?

Garlic is commonly used for nausea. Peppermint may also be helpful.

What is the dosing instruction for the scopolamine patch for motion sickness?

Apply 1 patch behind the ear at least 4 hours before the effect is needed; replace every 3 days as needed.

How long before travel should oral antihistamines for motion sickness be taken?

30-60 minutes prior to the needed effect.

Why should pilots or drivers avoid motion sickness medications?

They cause drowsiness and impair judgment.

What is the boxed warning regarding promethazine use in children?

Avoid use in children less than 2 years old and use with extreme caution in children 2 years and older due to risk of respiratory depression.

Are 5-HT3 receptor antagonists effective for motion sickness?

No, they are generally not effective.

What are the contraindications for scopolamine?

Hypersensitivity to belladonna alkaloids and closed-angle glaucoma.

What must be done with a scopolamine patch before an MRI?

Remove it, as it contains metal.

What substance should be avoided while using a scopolamine patch?

Alcohol

What are common side effects of scopolamine?

Dry mouth, drowsiness, dizziness, confusion, and vision changes (increased IOP & pupil dilation) withdrawal symptoms after discontinuation.

What happens if a patient touches their eyes after handling a scopolamine patch?

Stinging of the eyes and pupil dilation.

What is the primary difference between Dramamine and Dramamine Less Drowsy?

Dramamine contains dimenhydrinate, while Dramamine Less Drowsy contains meclizine.

What are the common warnings for antihistamines used in motion sickness?

CNS depression, worsening of BPH symptoms, and increased intraocular pressure (glaucoma).

What are commons side effects for antihistamines used for motion sickness?

Drowsiness, dizziness, dry eyes, blurry vision

Which antihistamine is most commonly used for vertigo?

Meclizine

Can you drive while using scopolamine patches? Why or why not?

No due to the high level of drowsiness, dizziness, and confusion

How should a scopolamine patch be applied to the skin?

Press firmly to the skin behind the ear for 30 seconds.

Why should you avoid placing a scopolamine patch over hair?

The hair may be removed when the patch is taken off.

What should be done if treatment with a scopolamine patch is needed for longer than 3 days?

Remove the first patch and place a new patch behind the other ear.

Why should scopolamine be avoided in elderly patients if possible?

Anticholinergic side effects are worse and not well-tolerated in this population.