Atropine serum concentrations after multiple inhaled doses of atropine sulfate

Atropine may be given by inhalation for bronchodilation. Intravenous atropine at doses of 0.32 to 1 mg yields serum levels of 2 to 6 ng/ml, with an elimination t1/2 of about 4 hours. Efficient inhalation of large single doses leads to similar concentrations in some individuals, but under clinical conditions drug delivery may be less efficient. Of concern is accumulation of the drug in the body with multiple-dose therapy. We measured serum levels of atropine after single inhaled doses and again after 48 to 72 hours of inhalation every 4 to 6 hours in 11 subjects. The drug was administered by therapists at doses and techniques commonly used in the clinical setting. Serum concentrations of atropine were negligible after the first dose in all subjects but were detectable in six of nine subjects who received the drug for more than 48 hours. Three of the subjects had levels greater than 2 ng/ml.