Atropine is well absorbed from the small bowel and not at all from the stomach. Thus the effects of oral dosing are much slower in onset than after parenteral dosing. Atropine is also absorbed by mucous membranes but less readily from the eye and skin, although significant toxicity can sometimes occur through absorption of excessive eye drops.
Atropine has a volume of distribution of 1 - 6 L/kg. Protein binding is moderate, with approximately 50% of the drug bound in plasma. Its plasma clearance is 8ml/min/kg.
Only traces of atropine are found in breast milk. The drug readily crosses the blood-brain barrier and may cause confusion and delirium post-operatively. It crosses the placenta readily.
Atropine is metabolised by hepatic oxidation and conjugation to inactive metabolites, with about 2% undergoing hydrolysis to tropine and tropic acid. About 30% of the dose is excreted unchanged in the urine. Only trace amounts of the dose are eliminated in the faeces.
There is some evidence of prolonged elimination in elderly subjects.