Drug interactions: inhibition of acetaminophen glucuronidation by drugs.

Glucuronidation of [3H]acetaminophen (APAP) was studied in rat liver preparations. Both Triton X-100 and UDP-N acetylglucosamine (UDPAG) activated 3- to 4-fold the glucuronidation of APAP by liver homogenates or microsomes. Prednisolone inhibited microsomal glucuronidation of APAP, yielding apparent noncompetitive kinetics in native and in UDPAG-activated microsomes. Studies with UDPAG-activated microsomal preparations show that many drugs can inhibit glucuronidation of APAP markedly; among the most poten inhibitors are: morphine, dicumarol, hydroxyzine, phenolphthalein, chloramphenicol and tetracycline.