JEE Main 2023 · 30 January · evening · Single correct · +4 / −1
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R .
Assertion A : Antihistamines do not affect the secretion of acid in stomach.
Reason R : Antiallergic and antacid drugs work on different receptors.
In the light of the above statements, choose the correct answer from the options given below:
- (a) A is false but R is true
- (b) Both A and R are true but R is not the correct explanation of A
- (c) Both A and R are true and R is the correct explanation of A
- (d) A is true but R is false
Answer and solution
Answer (c) Both A and R are true and R is the correct explanation of A
Solution
Chemistry ma’am · 3 steps
Histamine has two receptors: allergy drugs block one, antacids block the other.
- What histamine does. Histamine causes allergy symptoms such as itching and a runny nose. It also tells the stomach wall to release HCl and pepsin. It does these two jobs through two different receptors.
Drug type Examples Receptor blocked Effect Antihistamine (antiallergic) brompheniramine, terfenadine H₁ relieves allergy, no effect on stomach acid Antacid (H₂ blocker) cimetidine, ranitidine H₂ in the stomach wall cuts acid secretion - Check A and R. An antihistamine competes with histamine only at H₁ receptors. The H₂ receptors in the stomach stay free, so acid secretion does not change and A is true. Antiallergic and antacid drugs act on different receptors, so R is also true.
- So. R gives the exact reason for A: the antihistamine never reaches the receptor that controls acid. Both are true and R explains A, so the answer is (c).
The idea to keep. A drug acts only at the receptor it binds. Same messenger (histamine), different receptors (H₁ for allergy, H₂ for stomach acid), so the effects stay separate.
Answer from the NTA final answer key. Solution by PrepWiser.