EFFECT OF 3-METHYLCHOLANTHRENE PRETREATMENT ON BIOAVAILABILITY OF PHENACETIN IN RAT

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  • 1 January 1976
    • journal article
    • research article
    • Vol. 4  (4) , 402-406
Abstract
A TLC procedure is described for the quantitative determination of phenacetin and acetaminophen in rat plasma. The method was used to determine the effect of 3-methylcholanthrene (3-MC) on the disposition and bioavailability of phenacetin following its oral and i.v. administration to rats. Pretreatment with 3-MC decreased the plasma half-life of phenacetin, after i.v. administration, from 28 min to 4.5 min and reduced the systemic bioavailability of phenacetin, after oral administration, from 45% in control rats to 6% in 3-MC-treated rats. Comparison of the plasma levels of phenacetin in the portal circulation with those in the peripheral circulation, following the oral administration of phenacetin, indicated that the 7-fold reduction in the bioavailability of phenacetin observed in 3-MC treated rats was caused by a marked increase in the metabolism of phenacetin during its 1st pass through the liver.