Question
Which of the following is not true about the action of anticholinergic drugs?
| A. |
Atropine is a CNS depressant
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| B. |
Atropine causes mydriasis, abolition of light reflex and cycloplegia
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| C. |
Atropine causes bronchoconstriction
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| D. |
A&C
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Show Answer
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Correct Answer » D
Explanation
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Ans. C. Atropine causes bronchoconstriction
Ref KDT 7iVe p. 113, 114
Actions of anticholinergic drugs:
- These are opposite of parasympathetic (cholinergic) system.
- Atropine has an overall CNS stimulant action.
- Stimulates medullary centres – vagal, respiratory, vasomotor.
- Depresses vestibular excitation and has antimotion sickness property.
- Abbrevates refractory period of A-V node and facilitates A-V conduction, PR interval is shortened.
- Does not have any consistent or marked effect on BP.
- Used in arrhythmias like AV block and digitalis induced arrhythmia.
- Causes mydriasis due to contraction of circular muscles (constrictor pupillae), abolition of light reflex and cycloplegia (paralysis of accomodation).
- Increases intraocular tension → Contraindicated in glaucoma.
- Causes bronchodilatation and reduced airway resistance, especially in COPD and asthma patients.
- Relaxes urinary bladder, urinary retention may occur → contraindicated in benign prostate hypertrophy.
- Decreases sweat, salivary, tracheobronchial and lacrimal secretion.
- Decreases secretion of acid, pepsin and mucus in the stomach.
