Comparative haemodynamic effects of clonidine administered intramuscularly or intravenously to anaesthetized rats.

1. The acute haemodynamic effects of clonidine, 0.001-1.0 mg/kg, administered intramuscularly or intravenously, were studied in anaesthetized rats. 2. The direct pressor potency of clonidine was 100-fold greater following intravenous administration than after intramuscular injection, but hypotensive efficacy was equal by either route.