아트로핀

9.84

9.84

9.43

Atropine is an antimuscarinic agent that antagonizes the effects of acetylcholine. In small doses, atropine slows heart rate, and tachycardia develops due to paralysis of vagal control. Compared to [scopolamine], atropine has a more potent and prolonged effect on the heart, intestine and bronchial muscle, but a weaker effect on the iris, ciliary body and certain secretory glands. Atropine leads to increased respiratory rate and depth of respiration, possibly due to the drug-induced bronchiolar dilatation rather than its mild effect on vagal excitation. At an adequate dose, atropine abolishes different types of reflex vagal cardiac slowing or asystole. Atropine can be used to prevent or abolish bradycardia or asystole induced by the injection of choline esters, anticholinesterase agents or other parasympathomimetic drugs, and cardiac arrest produced by stimulation of the vagus. When vagal activity is an etiologic factor, atropine may also lessen the degree of partial heart block. In clinical doses, atropine counteracts the peripheral dilatation and abrupt decrease in blood pressure produced by choline esters. However, when given by itself, atropine does not exert a striking or uniform effect on blood vessels or blood pressure. The use of topical atropine in the eye induces mydriasis by inhibiting the contraction of the circular pupillary sphincter muscle normally stimulated by acetylcholine. This results in the contraction of the countering radial pupillary dilator muscle and pupil dilation. The use of atropine may precipitate acute glaucoma and convert partial organic pyloric stenosis into complete obstruction. Atropine may also lead to complete urinary retention in patients with prostatic hypertrophy and cause the thickening of bronchial secretions and formation of viscid plugs in patients with chronic lung disease.

Atropine binds to and inhibits muscarinic acetylcholine receptors, competitively blocking the effects of acetylcholine and other choline esters. It acts as a reversible non-specific antagonist of muscarinic receptors, showing affinity for the M1, M2, M3, M4 and M5 receptor subtypes. Atropine antagonizes the effects of acetylcholine on tissues innervated by postganglionic cholinergic nerves, such as smooth muscle, cardiac tissue, exocrine glands and the central nervous system. Also, it acts in less innervated smooth muscle that responds to endogenous acetylcholine. The actions of atropine can be overcome by increasing the concentration of acetylcholine at receptor sites (for instance, the use of anticholinesterase agents that inhibit the hydrolysis of acetylcholine).