Effect of exercise in sheep on the absorption of intramuscular atropine sulfate

In normal female sheep, we investigated effects of exercise on the absorption of atropine sulfate (0.02 mg/kg) given intramuscularly. The exercise regime consisted of treadmill running (20 min at 3-4 mph at 0 degrees grade) starting immediately after intramuscular atropine injection into the biceps femoris. Six normal female sheep received intramuscular atropine and 7-14 days later an identical intramuscular dose of atropine with exercise. Serum levels of atropine measured by radioimmunoassay were monitored over a 6-hour period. The time to peak concentration was significantly less with exercise than without, 2.9 +/- 2.1 and 13.7 +/- 5.4 min, respectively (p less than 0.005). In addition, peak serum atropine concentrations tended to be higher, 9.7 +/- 1.3 ng/ml with exercise versus 7.1 +/- 2.9 ng/ml without exercise; however, the difference did not attain statistical significance (p less than 0.08). This study demonstrates that exercise increases the early absorption of intramuscularly administered atropine sulfate.