Plasma kinetics of atropine and ipratropium in rats after different routes of administration evaluated by a radioreceptor assay.

: Plasma kinetics of atropine and ipratropium was assessed in rat after i.v. (10 mg/kg), oral and i.p. (50 mg/kg) administration by a radioreceptor assay (RRA). The volume of the central compartment and the clearance of both drugs were very similar (about 3 L/kg and 3.5 L/h/kg respectively) while the steady state volume of distribution and the terminal half-life of atropine were higher than those of ipratropium. After i.p. administration the kinetics of ipratropium was very different from what was expected after the i.v. experiment.