These enzymatic reactions may occur in the cytosol, plasma, and microsomes. The result is an increase in the half-life of the drug. Cimetidine, an H 2 histamine antagonist, inhibits the metabolism of many drugs. Implications for enzyme induction are important in drug therapy. As a consequence of reduced half-life, the duration of therapeutic effectiveness of a drug is reduced.
Many drugs induce specific enzymes.
Phenobarbital, clofibrate, and the polycyclic hydrocarbon compounds benzopyrene and 3-methylcholanthrene are examples. Some xenobiotics are metabolized to products that are carcinogenic. The result is cancer. Both phase I and phase II metabolisms are involved. Glutathione is important for detoxication in the metabolism of acetaminophen.