Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2019 Publisher: Mercury Pharmaceuticals Limited, Capital House, 85 King William Street, London, EC4N 7BL, UK
Pharmacotherapeutic group: Anticholinergic agents
ATC code: A03BA01
Atropine is an antimuscarinic agent which competitively antagonizes acetylcholine at postganglionic nerve endings, thus affecting receptors of the exocrine glands, smooth muscle, cardiac muscle and the central nervous system.
Peripheral effects include tachycardia, decreased production of saliva, sweat, bronchial, nasal, lachrymal and gastric secretions, decreased intestinal motility and inhibition of micturition.
Atropine increases sinus rate and sinoatrial and AV conduction. Usually heart rate is increased but there may be an initial bradycardia.
Atropine inhibits secretions throughout the respiratory tract and relaxes bronchial smooth muscle producing bronchodilatation.
Following intravenous administration, the peak increase in heart rate occurs within 2 to 4 minutes. Plasma levels after intramuscular and intravenous injection are comparable at one hour.
Peak plasma concentrations of atropine after intramuscular administration are reached within 30 minutes, although peak effects on the heart, sweating and salivation may occur nearer one hour after intramuscular administration. Atropine is distributed widely throughout the body and crosses the blood brain barrier.
Atropine is metabolised in the liver by oxidation and conjugation to give inactive metabolites.
The elimination half life is about 2 to 5 hours. Up to 50% of the dose is protein bound. It disappears rapidly from the circulation.
About 50% of the dose is excreted within 4 hours and 90% in 24 hours in the urine, about 30 to 50% as unchanged drug.
Non-clinical data reveal no special hazard for humans based on studies of safety pharmacology, repeated dose toxicity, genotoxicity and limited studies on carcinogenic potential. No adequate studies of reproductive toxicity have been performed.
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