Serum atropine concentrations after inhalation of atropine sulfate

Six male subjects with chronic bronchitis were given a single aerosol dose of atropine sulfate (0.05 mg/kg). Spirometry and venous blood samples were obtained before and at 0.25, 0.5, 1.0, 1.5, 2.0, and 4.0 h after inhalation of drug. All subjects had a satisfactory bronchodilator response and detectable serum concentrations of atropine within 15 min. Measurable serum concentrations persisted for 4 h with apparent continued slow absorption occurring throughout the entire time interval. The maximal concentrations achieved ranged from 1.3 to 5.8 ng/ml in five subjects. A sixth subject achieved much higher concentrations (as high as 21 ng/ml) and experienced systemic side effects. This latter concentration is comparable to those achieved with doses of 1.5 to 2.0 mg of parenteral atropine. Significant systemic absorption may occur after inhalation of atropine sulfate, although the degree of absorption is variabled.