Effects of etiocholanolone-induced fever on plasma antipyrine half-lives and metabolic clearance.

The plasma half-life and metabolic clearance rate of antipyrine, a drug metabolized by hepatic microsomal enzymes, were determined in 33 normal volunteers during a basal state and during fever induced with a single intramuscular injection of etiocholanolone. Of the 14 normal volunteers who achieved significant fever (fever index greater than 50), in 11 plasma antipyrine half-life was prolonged after a single oral dose of 10 mg/kg and antipyrine metabolic clearance rate was decreased. There was no significant change of these mean values in 19 normal volunteers who failed to develop significant fever (fever index smaller than 50). Therefore, under the conditions of this study plasma antipyrine half-life was prolonged, probably due to impaired hepatic metabolism, during etiocholanolone-induced fever, although no correlation was observed between the magnitude of fever and the extent to which plasma antipyrine half-life was prolonged. Failure to obtain such a correlation may be attributable to the very small range of temperature elevation, extending from 37.9 degrees C to 39.2 degrees C, in the group of 14 subjects achieving significant etiocholanolone-induced fever (fever index greater than 50). A higher dose of antipyrine (18 mg/kg) suppressed induction of fever by etiocholanolone; antipyrine is the only orally administered drug thus far shown to be effective in repressing etiocholanolone-induced fever.