Antihistamines used in motion sickness is
**Core Concept**
Antihistamines are a class of medications that block the action of histamine, a chemical involved in allergic reactions and various physiological processes. In the context of motion sickness, antihistamines are used to prevent the symptoms caused by the conflicting sensory inputs from the inner ear, eyes, and sensory nerves.
**Why the Correct Answer is Right**
The correct antihistamine used in motion sickness is **Dimenhydrinate**. It works by blocking the action of acetylcholine at the muscarinic receptors in the inner ear, which helps to reduce the sensitivity of the vestibular system to motion. This leads to a decrease in the conflicting sensory inputs that cause motion sickness. Dimenhydrinate also has a sedative effect, which can help to alleviate symptoms such as nausea and vomiting.
**Why Each Wrong Option is Incorrect**
**Option A:** **Diphenhydramine** is another antihistamine, but it is not the most commonly used one for motion sickness.
**Option B:** **Famotidine** is an H2 receptor antagonist, which is used to treat ulcers and gastroesophageal reflux disease, not motion sickness.
**Option C:** **Cyclizine** is an antihistamine that can be used to treat motion sickness, but it is not the most commonly used one.
**Clinical Pearl / High-Yield Fact**
When treating motion sickness, it's essential to start the medication before the onset of symptoms, as it's more effective in preventing symptoms than treating them after they occur.
**Correct Answer: C. Cyclizine**