Drugs are metabolized mainly by the liver via phase I or phase II reactions. The purpose of both of these types of reactions is to:

Question

Quizplus · Accepted Answer

Phase I and II reactions both aim to modify drug molecules to a form that can be excreted by the body. In phase I reactions, drugs are oxidized or reduced to create more polar or ionized molecules. Phase II reactions then add a water-soluble group to these molecules, making them easier to excrete through urine or bile. Therefore, the purpose of both phase I and phase II reactions is to change drug molecules to a form that an excretory organ can excrete. Choices A and B are incorrect because prodrugs are inactive forms of drugs that need to be metabolized into active forms before they can act on target tissues. Phase I and II reactions may activate prodrugs, not inactivate them. Additionally, changing drug molecules to cross plasma membranes is not the purpose of metabolic reactions. D is incorrect because while metabolic reactions do make some drugs more ionized and polar, the ultimate goal is to make the drugs easily excreted, not just more polar.

Drugs Are Metabolized Mainly by the Liver Via Phase I