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Clinical pharmacy 2024/2025 Level 3 Pharm D Pharmacology 1 (PO 502)

1- Muscarinic antagonists, parasympatholytic (Atropine-like)

 Effects of atropine:

➢ The first effect ➔ paradoxically transit bradycardia lasts for a few sec
➔ due to central stimulation of vagal activity.
CVS ➢ Slightly larger doses ➔ expected tachycardia due to block of cardiac

muscarinic activity.
 All secretions (Salivary, lacrimal, bronchial & sweat) are inhibited by

very low doses of atropine:
➢  Salivation ➔ dry mouth ➔ difficult swallowing (dysphagia) &
talking (dysphonia)
Secretions ➢  bronchial secretions
➢  Lacrimal secretions ➔ dry (Sandy) eye.

➢  Sweating ➔ dry skin ➔ atropine fever especially in children.
& ttt hyperhidrosis

 Gastric secretion is only slightly reduced (Pirenzepine inhibits gastric
acid secretion in doses that do not affect other systems➔ selective M1
antagonist which present in gastric mucosa & parietal cell)

Smooth ➢ GIT: ➔ GI motility is inhibited by atropine by larger doses
muscles ➢ Relaxation of bronchial, biliary & urinary tract smooth muscles
(urinary retention in elderly).

➢ Pupil is dilated "passive mydriasis" & become unresponsive to light
(Loss of light reflex) ➔ differentiate between atropine &
sympathomimetic ➔ cause active mydriasis

Eye ➢ Relaxation of ciliary muscle ➔ paralysis of accommodation
"Cycloplegia" ➔ near vision is impaired.
➢  Lacrimal secretions ➔ dry (Sandy) eye.

➢  IOP ➔ this is unimportant in normal individuals, but
contraindicated in-patients suffering from glaucoma.
➢ At low doses: Mild restlessness

CNS ➢ Higher doses: agitation & disorientation.
➢ Scopolamine (hyoscine) ➔ more depressant at therapeutic doses ➔
drowsiness, amnesia, fatigue & sleep.

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