Comparison of Pharmacokinetic and Pharmacodynamic Parameters following Oral or Intramuscular Atropine in Children

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Abstract
Pharmacokinetic and pharmacodynamic parameters of atropine 0.03 mg/kg p.o. [orally] or 0.02 mg/kg i.m. were compared in a double-blind study in 20 children with a mean age of 5.1 yr undergoing otolaryngological surgery, mostly adenotomy. Outside the study protocol, 2 small children accidentally received an overdose of atropine 0.3 mg/kg p.o. In addition to atropine, all children received triclofos 70 mg/kg p.o. Following p.o. administration of atropine, the mean maximum serum concentration of 6.7 nmol/l occurred at 2 h. The corresponding result after i.m. administration was 5.7 nmol/l at 0.5 h. Serum concentrations of atropine were 3.5 and 1.3 nmol/l 8 h after p.o. and i.m. administrations, respectively. At 70 min the antisialogogue effect was clinically satisfactory after both modes of administration. The heart rate increased statistically significantly only after i.m. administration. The mean maximum rise in the rectal temperature before the start of anesthesia occurred at 1 h and was 0.5.degree. C in the p.o. group and 0.7.degree. C in the i.m. group. The flush phenomenon, mostly on the face and sometimes also on the chest, occurred in both groups, being more intense in the i.m. group than in the p.o. group. The children who developed flush had a statistically significantly higher rise in rectal temperature than the children without flush. There was a positive but weak correlation between the serum concentration of atropine and the heart rate, whereas the correlation between the serum concentration after i.m. atropine and the rectal temperature was weakly negative. There were no decisive differences between the effects and side effects of the 2 modes of administration of atropine. Since many children are afraid of injections, oral administration of atropine is preferable to i.m. administration. The children who received an overdose of atropine besides triclofos were sedated, exhibited widely dilated, fixed pupils, were flushed and developed tachycardial and elevated temperature. Both children were fully recovered without special treatments 8 h after administration of atropine.