Pharmacokinetics of atropine in children

The serum concentration of atropine was determined both by radioreceptor assay (RRA) and by radioimmunoassay (RIA) following a single 0.02 mg/kg i.v. injection of 7 girls (age 6-15 years) and 16 boys (age 4-15 years) at the beginning of a combination anesthesia. RIA appeared to be useful in the clinical kinetic studies of this alkaloid, but RRA determined the whole antimuscarinic activity produced by atropine plus glycopyrrolate when the latter agent was used as an anticurarizing component together with neostigmine at the end of anesthesia. A biexponential serum decay curve of atropine was demonstrated by RIA with a very rapid distribution phase (t1/2 = 1-2 min) and a quite high tissue distribution (mean Vd beta = 2.6 l/kg), but due to the effective clearance of the drug (mean Cl total = 0.310-0.384 l/kg/h) the mean elimination phase half-life was around 6.5 hours. No age or gender dependency was found in the pharmacokinetics of atropine.