Effect of experimental hyperthyroidism on atropine pharmacokinetics in sheep

Atropine sulfate (0.02 mg/kg, i.m.) was administered to normal sheep and to sheep with experimentally induced hyperthyroidism. Serum and urine concentrations of atropine measured by radioimmunoassay were monitored over an 8-h period. The time to reach maximum serum concentration was similar in both hyperthyroid and normal sheep. A comparison between normal and hyperthyroid sheep indicated that the atropine absorption rate was not changed, but its rate of elimination was significantly greater in hyperthyroid sheep (p less than 0.01). Hyperthyroidism resulted in significant decreases in atropine (p less than 0.05), MRT (p less than 0.01), AUC (p less than 0.01) and an increase in C1/F (p less than 0.01) when compared to atropine kinetics of normal sheep.