Features of atropine poisoning are all of the following except: March 2011
Correct Answer: Hypothermia
Description: Ans. B: Hypothermia Sign and symptoms of atropine poisoning are due to peripheral muscarinic blockade (dilatation of pupils, hyperpyrexia due to inhibition of sweating) and central effects (initial stimulation and subsequent depresion of CNS; confusion and hallucination) Atropine It is a naturally occurring tropane alkaloid extracted from deadly nightshade (Atropa belladonna), Jimson weed (Datura stramonium), mandrake (Mandragora officinarum) and other plants of the family Solanaceae. Atropine increases firing of the sinoatrial node (SA) and conduction through the atrioventricular node (AV) of the hea, opposes the actions of the vagus nerve, blocks acetylcholine receptor sites, and decreases bronchial secretions. Atropine lowers the parasympathetic activity of all muscles and glands regulated by the parasympathetic nervous system. This occurs because atropine is a competitive antagonist of the muscarinic acetylcholine receptors (acetylcholine being the main neurotransmitter used by the parasympathetic nervous system). Therefore, it may cause swallowing difficulties and reduced secretions Adverse reactions to atropine include ventricular fibrillation, supraventricular or ventricular tachycardia, dizziness, nausea, blurred vision, loss of balance, dilated pupils (mydriasis), photophobia, dry mouth and potentially extreme confusion, dissociative hallucinations and excitation especially amongst the elderly. These latter effects are because atropine is able to cross the blood-brain barrier The antidote to atropine is physostigmine or pilocarpine. A common mnemonic used to describe the physiologic manifestations of atropine overdose is: as per Jon Blinkey "hot as a hare, blind as a bat, dry as a bone, red as a beet, and mad as a hatter". These associations reflect the specific changes of warm, dry skin from decreased sweating, blurry vision, decreased sweating/ lacrimation, vasodilation, and central nervous system effects on muscarinic receptors, type 4 and 5. This set of symptoms is known as anticholinergic toxidrome, and may also be caused by other drugs with anticholinergic effects, such as diphenhydramine, phenothiazine antipsychotics and benztropine
Category:
Pharmacology
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