The plasma half life and clearance of antipyrine was investigated in patients during the acute phase and again during the recovery phase of viral hepatitis. Each patient served as his own control, thereby eliminating genetic factors and minimising environmental factors that cause large interindividual variations in antipyrine elimination rates. Liver function tests, antipyrine, half life, plasma clearance, and the apparent volume of distribution were determined in the acute and recovery period. It was found that the apparent volume of distribution of antipyrine did not change in five of six patients as they recovered. Five of the six patients showed prolonged plasma half lives and decreased plasma clearance of the drug at the time of acute illness and these parameters reached normal values during recovery. The plasma half life and clearance of the drug did not correlate with biochemical indices of liver function in the acute or recovery phase. This demonstration supports the concept that drug metabolism is frequently impaired in liver disease.
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