The Question is from neet-chemistry principles-related-to-practical-chemistry , and it was created by the author A.RAMA NAGESWARARAO

Question

Which antihistamine is LEAST likely to cause drowsiness?

A.RAMA NAGESWARARAO · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
	**Primary Concept**: Antihistamine properties and side effects
	**Related Topics**: Pharmacology, Allergy medication
	**Prerequisites**: Basic understanding of antihistamines and their mechanisms of action.
## SOLUTION PATHWAY
**Given Information**:
	The question asks to identify the antihistamine least likely to cause drowsiness among the given options.
	Options: Diphenhydramine, Promethazine, Fexofenadine, Hydroxyzine
**Method & Steps**:
	1. Understand the mechanism of action: Antihistamines block histamine receptors.  First-generation antihistamines (like diphenhydramine and promethazine) readily cross the blood-brain barrier, leading to sedative effects. Second-generation antihistamines (like fexofenadine) have less ability to cross the blood-brain barrier.
	2. Analyze each option:
		Diphenhydramine and Promethazine are first-generation antihistamines known for their strong sedative effects.
		Fexofenadine is a second-generation antihistamine, specifically designed to minimize central nervous system effects, thus less likely to cause drowsiness.
		Hydroxyzine is also known to cause drowsiness.
	3. Identify the least sedating option: Based on their known properties, fexofenadine is the least likely to cause drowsiness among the given choices.
		Result: Fexofenadine
		Verification:  This aligns with established pharmacological knowledge of antihistamines.
## OPTION ANALYSIS
A :x: Diphenhydramine is a first-generation antihistamine known for its strong sedative effects.
B :x: Promethazine is also a first-generation antihistamine with significant sedative properties.
C ✓: Fexofenadine is a second-generation antihistamine; it is less likely to cause drowsiness due to its lower ability to cross the blood-brain barrier.
D :x: Hydroxyzine has sedative effects as a side effect.
## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing first and second-generation antihistamines:  Remembering the key difference in their ability to cross the blood-brain barrier is crucial.
		2. Relying on personal experience rather than established pharmacological knowledge: Anecdotal evidence may vary.
	**Quick Tips**:
		1. Remember that second-generation antihistamines are generally less sedating than first-generation ones.
		2.  Associate 'sedation' with first-generation antihistamines like diphenhydramine and promethazine.

A.RAMA NAGESWARARAO · Answer

Diphenhydramine

A.RAMA NAGESWARARAO · Answer

Promethazine

A.RAMA NAGESWARARAO · Answer

The correct Option is "Fexofenadine"

A.RAMA NAGESWARARAO · Answer

Hydroxyzine

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