Atropine

Atropine:
• main drug in this class; derived from the deadly nightshade plant; belladonna alkaloid
• competitive blocking at muscarinic receptors – has no direct effect on its own ( have no effect in the absence of acetylcholine)
• prevents receptor being activated by acetylcholine or muscarinic agonist
• can also affect nicotinic receptors at high doses; well absorbed from gut
• effects are opposite to that of muscarinic agonists – increases heart rate; decreases secretion from exocrine glands; relaxation of bronchi; decrease tone of urinary bladder; decreased tone and motility of gastrointestinal tract; dilation of pupil in eye; mild CNS excitation
• used for pre-anaesthetic medication to reduce secretions; bradycardia; peptic ulcers; asthma
• side effects – due to block of muscarinic receptor – eg dry mouth, blurred vision, photophobia, dry eyes, increased intraoccular eye pressure, retention of urine, constipation, anhidrosis, tachycardia, reduced sweating, drowsiness, hallucinations

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