ATROPINE
Atropine is a naturally occurring tropane alkaloid extracted from deadly nightshade (Atropa belladonna), jimsonweed (Datura stramonium), mandrake (Mandragora officinarum) and other plants of the family Solanaceae. It is a secondary metabolite of these plants and serves as a drug with a wide variety of effects. It is a competitive antagonist for the muscarinic acetylcholine receptor. It is classified as an anticholinergic drug (parasympatholytic). The name comes from the original use in deadly nightshade as a way of dilating women’s pupils to make them beautiful. As such both atropine and deadly nightshade derive names from Atropos, one of the three Fates who, according to Greek mythology, chose how a person was to die. Atropine is a core medicine in the World Health Organization’s “Essential Drugs List”, which is a list of minimum medical needs for a basic health care system
effects and uses
Atropine increases firing of the sinoatrial node (SA) and conduction through the atrioventricular node (AV) of the heart, opposes the actions of the vagus nerve, blocks acetylcholine receptor sites, and decreases bronchial secretions.
In general, 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.
Side-effects and overdose
Adverse reactions to atropine include ventricular fibrillation, supraventricular or ventricular tachycardia, dizziness, nausea, blurred vision, loss of balance, dilated pupils, 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. Because of the hallucinogenic properties, some have used the drug recreationally, though this is potentially dangerous and often unpleasant.
In overdoses, atropine is poisonous. Atropine is sometimes added to potentially addictive drugs, particularly anti-diarrhea opioid drugs such as diphenoxylate or difenoxin, wherein the secretion-reducing effects of the atropine can also aid the anti-diarrhea effects.
Although atropine treats bradycardia (slow heart rate) in emergency settings, it can cause paradoxical heart rate slowing when given at very low doses, presumably as a result of central action in the CNS.[6]
Atropine is incapacitating at doses of 10 to 20 mg per person. Its LD50 is estimated to be 453 mg per person (per oral) with a probit slope of 1.8.[7] 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”.[8] 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.[9]
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