Antipyrine metabolism in acute hepatic porphyria in relapse and remission.

Antipyrine kinetics following a single oral dose were obtained in porphyric patients in attack and in remission and in controls. The clearance of antipyrine was significantly lower during an acute porphyric attack (median: 0.34 ml min-1 kg-1; range: 0.1-0.71, P less than 0.05) than in patients in remission (median: 0.53 ml min-1 kg-1; range: 0.28-0.87) or controls (median: 0.52 ml min-1 kg-1; range: 0.32-0.93). There was a significant negative correlation between weight-adjusted antipyrine clearance and the urinary excretion of the porphyrin precursors, delta-aminolaevulinic acid (r = 0.86, P less than 0.001) and porphobilinogen (r = 0.82, P less than 0.002). These data suggest that the more severe the porphyric attack, the greater the impairment of hepatic monooxygenase activity.