The influence of elevated plasma hydrocortisone concentrations on antipyrine metabolism in man.

1 The plasma half-life of antipyrine was estimated overnight in four healthy volunteers on two separate occasions, one during i.v. infusion of hydrocortisone (3 mg/h) and the second during an infusion of normal saline. 2 The plasma fluorogenic corticosteroid concentration averaged 12.5 μg/100 ml during saline infusion, increasing to 20.1 μg/100 ml during hydrocortisone infusion. 3 The mean antipyrine half-life increased from 9.7 h during saline infusion to 12.6 h during hydrocortisone infusion. 4 No consistent change was found in the apparent volume of distribution or urinary excretion of antipyrine, or of the urinary excretion of D-glucaric acid. 5 The stimulation by hydrocortisone of antipyrine metabolism demonstrated by other workers has not been found.