Metabolism and Excretion

Question 1

Describe drug metabolism

Answer 1

When drugs are metabolized, they are chemically altered by enzymes into new molecules called metabolites.
Metabolism can increase or decrease the onset, duration of action, and toxicity of a medication

Question 2

What is the goal of metabolism

Answer 2

More water soluble so they can be excreted by the kidneys

Question 3

Where does metabolism mostly occur

Answer 3

Can occur in every biological tissue but mostly in the smooth endoplasmic reticulum of cells in the liver

Question 4

What is first-pass metabolism

Answer 4

metabolism by the liver following oral administration and is important in determining whether a drug can be orally administered

Question 5

What is the large family of enzymes responsible for metabolizing a large amount of drugs

Answer 5

Cytochrome P450 (CYP450)

Question 6

How many human CYPs have been isolated so far

Answer 6

50

Question 7

What is the major CYP subfamily expressed in the human liver?

Answer 7

CYP3As

Question 8

What are Single Nucleotide Polymorphisms (SNPs) and how are they expressed

Answer 8

Minor mutations in proteins that can result in metabolic activity changes.
When SNP variations exist in the individual CYP enzyme, they are named by an asterisk and a number showing the order in which each SNP was identified

Question 9

Describe Phase 1 Metabolism

Answer 9

Nonsynthetic Rxns.
-involve oxidation, reduction, and hydrolysis reactions
-rxns introduce or unmask polar groups that, in general, improve water solubility and prepare drug molecules for further metabolic reactions.
-can result in metabolites with greater or lesser pharmacological activity
-Many phase I metabolites are eliminated and others move on to Phase II.

Question 10

Describe Phase II Metabolism

Answer 10

Synthetic Rxns
Something is added to the drug to synthesize a new compound. Goal is to add something to make it more polar, making it more water soluble and easier to excrete.

Question 11

Describe First Order Metabolism

Answer 11

Characterized by a half-life, the time period over which the drug concentration will decrease by half.
Therefore, blood levels decrease by 50% in one half-life, 75% in two half-lives, and 87.5% in three half-lives

Question 12

Describe Zero-Order Metabolism

Answer 12

Enzymes act near to their maximal metabolic capacity and metabolize a constant amount of drug each hour.

Question 13

What is a prodrug

Answer 13

inactive compounds that rely on metabolism to become active

Question 14

What determines which drug will be metabolized first if there is competition between drugs and enzyme

Answer 14

When several drugs are metabolized by a single enzyme, each drug will be metabolized in proportion to the affinity for each of the drug–enzyme interactions

Question 15

What does grapefruit juice due to the CYP3A4 enzyme

Answer 15

inhibits CYP3A4 and can sometimes markedly increase blood levels of drug in patients consuming grapefruit juice.

Question 16

What is excretion?

Answer 16

Locations at which drugs can pass from inside the body to outside. Include some sites that are familiar as sites of absorption, such as lungs, skin, and intestines.

Question 17

What are the unique sites of excretion where drug is only excreted and not absorbed

Answer 17

Kidneys and Gallbladder

Question 18

The production of urine begins where

Answer 18

glomerulus

Question 19

What is ultrafiltration

Answer 19

a process in which substances in the plasma pass through small holes, or pores, into the glomerular capillary

Question 20

Which part of the nephron primarily has the active transport systems needed to reabsorb important molecules

Answer 20

Proximal tubule. Important for endogenous reabsorption of ions, amino acids, and glucose

Question 21

What are the 3 types of active transport in the biliary excretion system

Answer 21

organic anion, organic cation, and bile acid transport

Question 22

What is an example of a drug excreted through the bile acid transport

Answer 22

digoxin

Question 23

What is enterohepatic cycling

Answer 23

when drug is excreted in the bile, absorbed from the intestines, and then excreted in the bile again
decreases the amount of drug that is actually excreted and extends the time that a drug remains in the body.

Question 24

Besides kidney and gallbladder, name a few other ways drugs can be excreted

Answer 24

breathing (ethanol, NO2), skin, saliva, breast milk