PLASMA-CONCENTRATION FOLLOWING ORAL AND INTRAMUSCULAR ATROPINE IN CHILDREN AND THEIR CLINICAL EFFECTS

In a paediatric population, we compared i.m, v oral atropine premedica tion to a control group without atropine and determined atropine plasm a concentrations (APC). Forty-five children were randomly assigned to one of three groups. Group I received atropine, 20 mu g . kg(-1) i.m., 15 min prior to induction. Group II received atropine, 30 mu g . kg(- 1) orally group III received no atropine. APC (expressed as percent of muscarine-2 receptor subtype occupancy), heart rate, rectal temperatu re, and salivation were determined before atropine, and 15, 25, 45, 60 , 90, 120 (no APC), and 150 min following atropine. Only 10-20% of the M2-cholinoceptors were occupied after oral atropine with a peak at 90 min compared to 60-70% occupancy with a peak 25 min after i.m. atropi ne. The peak in M2-cholinoceptor occupation in group I was paralleled by a peak percentage change in heart rate of 15% from baseline. The pe ak in receptor occupation in group II did not correspond to the peak i ncrease in heart rate. The percentage change of heart rate over time w as not significantly different from baseline values in any of the grou ps. Bradycardia or temperature changes did not occur in any of the gro ups. Antisialogogue effects were observed only in group I. We conclude that atropine, 30 mu g . kg(-1) orally is not an equipotent dosage to atropine, 20 mu g . kg(-1) i.m.