Metabolism & Excretion

Question 1

drug metabolism is

Answer 1

chemical reaction that occurs inside the body to reduce lipid solubility, alters biological activity thereby converting the drug into water-soluble to facilitate excretion from the body.

Question 2

organs involves in metabolism are

Answer 2

Liver (the main organ of metabolism)
Kidney
Intestine
Lungs
Skin
Adrenal gland 
Brain

Question 3

aims of drug metabolism are

Answer 3

To convert active drug into inactive substances.
To convert active drug into active metabolite. E.g. codeine  morphine
To convert inactive drug (prodrug)into active drug. E.g. Levodopa  dopamine
To convert active drug to toxic substances. E.g. Paracetamol  N-Acetyl Benzoquinone (hepatotoxic)

Question 4

What is half life?

In general, a drug will be eliminated after___half lives?

Answer 4

Time taken by a drug to become half of its initial concentration.
Generally, a drug will be eliminated after 6 half-lives.

Question 5

Outline drug metabolizing enzymes

Answer 5

Microsomal enzymes
Located in SER of liver, kidney, lungs & intestine.
Catalyse oxidation, reduction, hydrolysis and glucuronide conjugation
Ex: cytochrome P450, glucoronyl transferase

Non-microsomal enzymes
Present in cytoplasm and mitochondria of the liver, plasma, brain and kidney.
Ex: MAO (Mono amine oxidase), COMT (Catechol-o-Methyl transferase)

Question 6

Describe cytochrome system

Answer 6

Consists of more than 100 different isoenzymes that divided in families
Most significant: CYP1, CYP2, CYP3
Subfamilies:
CYP3A –causes about 50% biotransformation
CYP2D -causes about 20% biotransformation
CYP2C -causes about 15 % biotransformation

Question 7

_____ inhibit drug metabolising enzymes thereby decreasing the metabolism of drug

Answer 7

cimetidine

Question 8

____ induce drug-metabolizing enzymes by enhancing the rate and extent of enzymes synthesis

Answer 8

rifampicin

Question 9

drugs are eliminated from the body either converted to ___ or ____

Answer 9

metabolites, unchanged form

Question 10

define drug excretion

Answer 10

transportation of unaltered or altered drug out of the body

Question 11

renal, hepatobiliary and pulmonary are

Answer 11

major routes of drug excretion

Question 12

drug elimination processes are

Answer 12

glomerular filtration, active tubular secretion, tubular reabsorption

Question 13

free drug that are not bound to plasma protein are excreted through

Answer 13

glomerular filtration

Question 14

at proximal tubule,

Answer 14

charged molecules are transferred from plasma to tubular fluid

Question 15

reabsorption results in

Answer 15

increase half life of the drug

Question 16

lipid-soluble drug will be reabsorbed at

Answer 16

distal convoluted tubule

Question 17

gaseous and volatile substances are absorbed and excreted through lungs by

Answer 17

simple diffusion

Question 18

weak basic drugs such as ____ are excreted through breast milk

Answer 18

tetracycline, morphine

Question 19

a constant amount of drug is eliminated per unit time

Answer 19

zero order kinetics

Question 20

first-order kinetics

Answer 20

a constant fraction of drug is eliminated er unit time

Question 21

oxidation involves two types

Answer 21

microsomal and non-microsomal oxidation

Question 22

addition of O2/ -ve radical or removal of H+/+ve radical are involves in

Answer 22

oxidation process

Question 23

pentosil is reduced to sulphonamide are example of

Answer 23

reduction process of drug metabolism in phase 1

Question 24

hydrolysis

Answer 24

cleavage of drug molecule by taking up a molecule of water

Question 25

phase 2 involves

Answer 25

glucoronidation, acetylation, methylation, sulphating, glycine conjugation

Question 26

factors affecting drug metabolism

Answer 26

genetic factors, age, gender, diseases

Question 27

grapefruits juice inhibits

Answer 27

CYP3A metabolism of co-administered drug substrates

Question 28

lipid soluble drugs are not readily eliminated until

Answer 28

they are metabolises to more polar compounds

Question 29

____ will greatly impairs the elimination of drugs especially those that are primarily excreted by kidney

Answer 29

renal dysfunction

Question 30

decreased pharmacological effects of drugs are effects of

Answer 30

enzyme induction

Question 31

if primaquine, aspirin, and sulfonamides are given in glucose-6-PO4 deficiency person, it can cause

Answer 31

severe haemolysis