Determination of atropine in plasma by a direct radioreceptor assay.

A highly sensitive radioreceptor assay for the anticholinergic atropine was developed and could be applied directly to plasma samples obtained from mini-pigs without any clean-up. Plasma samples were collected during 6 h after atropine was administered intravenously or endobronchially. The endobronchial plasma concentration-time curves were characterized by a very rapid rise of the concentration but with a subsequent much slower decrease than after intravenous administration. This indicates an initially high as well as prolonged uptake from the lungs.