ABSTRACT
Most drugs are normally ingested via the gastrointestinal tract, and after absorption are transported by the portal vein to the liver, where they tend to accumulate and undergo metabolism. Most drugs, like other chemicals which are foreign to the body's own chemistry, are metabolized and transformed into other substances, irrespective of whether the drug is toxic or innocuous. In the case of toxic drugs, metabolism can play an important role in reducing or increasing the toxic effects, for a compound may produce signs of poisoning either because it is toxic per se, or because it is converted into a toxic substance. Since the enzymes responsible for the metabolism of drugs are localized in microsomes, they are normally referred to as “microsomal drug-metabolizing enzymes”. The metabolic changes of drugs are, in general, brought about by enzymes located in the endoplasmic reticulum, which is a complex system of membranes forming a network within the cell.
