The effects of exercise and adrenaline infusion upon the blood levels of propranolol and antipyrine in the horse.

There are now several examples showing that experimentally induced changes in hepatic blood flow can have a marked effect upon the elimination of certain high clearance drugs. Changes in hepatic blood flow produced by exercise might therefore be expected to influence the clearance of these drugs. There was an increase of up to 100%, compound to control values, in the plasma levels of propranolol in horses given either d- or dl-propranolol, 0.2 mg/kg b.wt., and then subjected to sustained exercise for 30 minutes. There was, however, no similar increase with exercise in the plasma levels of antipyrine in horses given antipyrine, 50 mg/kg b.wt. Intravenous infusions of adrenaline, 1 microgram/kg b.wt./min for 10 minutes also produced an increase of about 70% in the plasma levels of d-propranolol.