PS268 Chapter Notes - Chapter 5: Cytochrome P450, Fluoxetine, Blood Plasma
Drug Metabolism and Deactivation
For a drug to cease having an effect, one of two things must happen:
1) it is excreted from body
-usually in urine
2) it must be chemically changed so it no longer has the same effect on body
-most common way is for liver enzymes to act on drug molecules to change chemical
structure
-drugs are being removed or metabolized by the body as soon as administered
Some substances are not easily removed (ex heavy metals) and accumulate, having 2 effects:
1) metabolite no longer has the same action as the drug molecule
2) metabolite is more likely to be excreted by the kidneys
Kidneys operate in a 2 stage process:
1) water and most of the small and water soluble molecules are filtered out
2) most of the water is reabsorbed, along w some kind of the dissolved chemicals
-the more lipid soluble molecules are more likely to be reabsorbed
-liver enzymes can make drug molecules more water soluble and less lipid soluble, thus
harder to be reabsorbed
-all drugs are eliminated from the body in a chemically altered (metabolized) form or by
excretion
Document Summary
For a drug to cease having an effect, one of two things must happen: it is excreted from body. Usually in urine: it must be chemically changed so it no longer has the same effect on body. Most common way is for liver enzymes to act on drug molecules to change chemical structure. Drugs are being removed or metabolized by the body as soon as administered. Some substances are not easily removed (ex heavy metals) and accumulate, having 2 effects: metabolite no longer has the same action as the drug molecule, metabolite is more likely to be excreted by the kidneys. Kidneys operate in a 2 stage process: water and most of the small and water soluble molecules are filtered out, most of the water is reabsorbed, along w some kind of the dissolved chemicals. The more lipid soluble molecules are more likely to be reabsorbed.
