Atropine (Molecule of the Month for November 2009)
Atropa belladonna, Mandrake, Solanaceae
Atropine is a 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. The name comes from the original use in deadly nightshade (Atropa belladonna) 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. Mandragora (mandrake) was described by Theophrastus in the fourth century B.C. for treatment of wounds, gout, and sleeplessness, and as a love potion. By the first century A.D. Dioscorides recognized wine of mandrake as an anaesthetic for treatment of pain or sleeplessness, to be given prior to surgery or cautery. The use of Solanaceae containing tropane alkaloids for anesthesia, often in combination with opium, persisted throughout the Roman and Islamic Empires and continued in Europe until superseded by the use of ether, chloroform, and other modern anesthetics. Atropine extracts from the Egyptian henbane were used by Cleopatra in the last century B.C. to dilate her pupils, in the hope that she would appear more alluring. In the Renaissance, women used the juice of the berries of Atropa belladonna to enlarge the pupils of their eyes, for cosmetic reasons; "bella donna" is Italian for "beautiful lady". This practice resumed briefly in the late nineteenth- and early twentieth-century in Paris. The mydriatic effects of atropine were studied among others by the German chemist Friedlieb Ferdinand Runge (1795–1867). In 1831, the pharmacist Mein succeeded the pure crystalline isolation of atropine. The substance was first synthesized by German chemist Richard Willstätter in 1901.
Atropine is a racemic mixture of D-hyoscyamine and L-hyoscyamine, with most of its physiological effects due to L-hyoscyamine. Its pharmacological effects are due to binding to muscarinic acetylcholine receptors.
Atropine is indicated when excessive (or sometime normal) muscarinic effects are judged to be life threatening or are producing symptoms sever enough to call of temporary, reversible muscarinic blockade. Examples, not an exhaustive list, of such possible uses are: As an antisialogogue when reduction of secretions of the respiratory tract are thought to be needed; its routine use as a preanesthetic agent is discouraged; To blunt the increased vagal tone (decreased pulse and blood pressure) produced by intra-abdominal tract or ocular muscle traction, its routine use to prevent such events is discouraged; To temporarily increase heart rate or decrease AV-block until definitive intervention can take place, when bradycardia or AV-block are judged to be hemodynamically significant and thought to be due to excess vagal tone; As an antidote for inadvertent overdose of cholinergic drugs or for cholinesterase poisoning such as from organophosphorus insecticides; As an antidote for the "rapid type of mushroom poisoning due to the presence of the alkaloid muscarine, in certain species of fungus such as Amanita muscaria; and To alleviate the muscarinic side effects of anticholinesterase drugs used for reversal of neuromuscular blockade.
Update by Karl Harrison
(Molecule of the Month for November 2009 )