Atropine, C17H23NO3, M 289,4 g/mol.
To the Tropan alkaloids belonging physiological active substance derived especially from the deadly nightshade (Atropa belladonna) and other nightshade plants. Atropine was already used in the Middle Ages as mydriaticum, since it leads, instilled into the eyes, to a pupil dilation ("fiery view"). Medical use as antidote against poisonings with thiophosphoric ester (e.g. insecticides) as well as Muscarin- or Pilocarpin-poisoning.
Chemically atropine is a racemic mixture of (R,S)-Hyoscyamine, whereby however only (S)-Hyoscyamine is the active isomer. Atropine excretion is about 50% as unchanged drug over the urine, 24% as Noratropine after demethylation, and about 15% is oxigenated to the N-oxide. As site reaction a hydrolysis of atropine (ester) takes place by esterases, leading to Tropin (3α-Tropanol) and Tropic acid (3-Hydroxy-2-phenylpropionic acid).
For hypersensitive individuals already a dose of 1-2 mg atropine can act toxically.Usually doses above 10 mg causes toxic symptoms (tachycardia, hypertension, fever, delirious behavior). Doses greater than 50 mg can be fatal. Physostigmine can be used as antidote.