Pharmacokinetics Principles 2 (absorption and distribution)

Question 1

list the 4 steps of pharmacokinetics?

Answer 1

1- absorption.
2- distribution.
3- metabolism.
4- excretions.

Question 2

the transfer of a drug from the site of administration to the blood stream

Answer 2

absorption of drugs.

Question 3

absorption depends on 2 factors, what are they?

Answer 3

1- drug’s chemical characteristics.
2- route of drug administration.

Question 4

what is the most importants site of absorption for orally administered drugs?

Answer 4

small intestine.

Question 5

bioavailability for I.V delivery is ___%

Answer 5

100%

Question 6

for absorption to happen drugs need to cross _______

Answer 6

biological membranes.

Question 7

list the 4 mechanisms of absorption

Answer 7

1- passive diffusion.
2- facilitated diffusion.
3- active transport.
4- endocytosis and exocytosis.

Question 8

in passive diffusion drugs move ____ (along, against) the concentration gradient?

Answer 8

along.
from higher conc. to lower conc.

Question 9

which mechanisms of absorption don’t need energy?

Answer 9

passive diffusion and facilitated diffusion.

Question 10

which mechanism of absorption is not saturable?

Answer 10

passive diffusion.

Question 11

in facilitated diffusion carrier proteins undergo which type of change to transport drugs?

Answer 11

conformational change.

Question 12

in facilitated diffusion, drugs move ____ (along, against) conc. gradient.

Answer 12

along the conc gradient, higher to lower.

Question 13

which mechanisms of absorption are saturable?

Answer 13

facilitated diffusion and active transport.

Question 14

facilitated diffusion is inhibited by drugs that ______ for the carrier.

Answer 14

compete.

Question 15

in active transport, drugs move ____ (along, against) conc. gradient.

Answer 15

against.
lower to higher.

Question 16

which mechanism of absorption is selective?

Answer 16

active transport.

Question 17

active transport can be competitively ____ by other co-transported substances?

Answer 17

inhibited.

Question 18

engulfment of the drug by the cell membrane and transport in the cell in a drug-filled vesicle.

Answer 18

endocytosis

Question 19

endocytosis and exocytosis are used for the transport of drugs of ____ size across membranes

Answer 19

large.

Question 20

_______ is absorbed by endocytosis from the GIT?

Answer 20

vitamin B12.

Question 21

_________ are stored in vesicles and released by exocytosis?

Answer 21

neurotransmitters.

Question 22

list the 5 factors affecting absorption?

Answer 22

1- pH.
2- blood flow to the absorption site.
3- total surface area available for absorption.
4- contact time at the absorption surface.
5- expression of P-glycoprotein.

Question 23

ionized forms of drugs are _____ (lipid, water) soluble.

Answer 23

water

Question 24

unionized forms of drugs are _____ (lipid. water) soluble.

Answer 24

lipid

Question 25

__________ (ionized, unionized) form is better absorbed?

Answer 25

unionized.

Question 26

A drug crosses biological membrane readily if it is ______

Answer 26

uncharged.

Question 27

weak acids are unionized at _____ pH.

Answer 27

acidic

Question 28

weak bases are unionized at ____ pH.

Answer 28

basic.

Question 29

the pH at which the drug is 50% ionized

Answer 29

pKa of a drug.

Question 30

the _____ pKa of a drug the more acidic it is

Answer 30

lower.

Question 31

give an example of an acidic drug that gets largely unionized at gastric pH

Answer 31

aspirin

Question 32

where are basic drugs absorbed from?

Answer 32

the intestine.

Question 33

greater the blood flow to the absorption site the ____ is the absorption

Answer 33

more

Question 34

shock ____ absorption from subcutaneous route.

Answer 34

decreases.

Question 35

greater the surface area. ____ is the absorption

Answer 35

more

Question 36

more is the contact time, _____ is the absorption

Answer 36

more

Question 37

in areas of high expression.P-glycoprotein ______ drug absorption.

Answer 37

reduces.

Question 38

P-glycoprotein is associated with what?

Answer 38

associated with multidrug resistance.

Question 39

where is P-glycoprotein expressed?

Answer 39

liver, kidneys, placenta, intestines, and brain capillaries.

Question 40

fraction of administered drug that reaches the systemic circulation in unchanged form

Answer 40

bioavailability

Question 41

bioavailability is important for calculating drug doses for which administration route?

Answer 41

non-intravenous.

Question 42

bioavailability of i.v given drug is ___%?

Answer 42

100%

Question 43

list the 4 factors affecting bioavailability?

Answer 43

1- first- pass hepatic metabolism. 2- solubility of drug. 3- chemical instability. 4- nature of drug formulation.

Question 44

bioavailability of penicillin and insulin when given orally is ___?

Answer 44

0%

Question 45

how does first pass metabolism affect bioavailability?

Answer 45

the amount of drug that reach the systemic circulation in unchanged form is decreased.

Question 46

90% of _____ (which drug?) is cleared during a single passage through the liver, which is why it is given through the ______ route.

Answer 46

nitroglycerine, sublingual route.

Question 47

for a drug to be absorbed it must be ___ in aqueous solutions.

Answer 47

soluble

Question 48

drugs which are poorly soluble have ___ bioavailability.

Answer 48

low

Question 49

list the 4 factors that influence the ease of dissolution?

Answer 49

1- particle size. 2- salt form. 3- enteric coatings. 4- presence of excipients.

Question 50

2 related drug preparations are bioequivalent if the show _____________ and ____________________

Answer 50

complete bioavailability, and similar times to achieve peak blood concentration.

Question 51

the process by which a drug reversibly leaves the blood stream and the extracellular fluid and tissues

Answer 51

drug distribution

Question 52

list the 4 factors that affect drug distribution

Answer 52

1- differences in regional blood flow. 2- binding of drugs to plasma proteins and tissue proteins. 3- presence of tissue-specific transporters. 4- lipid solubility.

Question 53

what is the most common protein drugs bind to?

Answer 53

albumin

Question 54

redistribution happens only in ___ ____ soluble drugs.

Answer 54

highly lipid soluble drugs.

Question 55

give an example of a drug that undergoes redistribution

Answer 55

thiopentone sod. an anaesthetic.

Question 56

the BBB limits the entry of _____ soluble drugs into the CNS.

Answer 56

non-lipid soluble drugs.

Question 57

inflammation of the meninges _____ permeability of the BBB

Answer 57

increases.

Question 58

acidic drugs bind to _____ (which protein?) and basic drugs bind to ______ (which protein?)

Answer 58

acidic = plasma protein. basic = alpha 1 acid glycoprotein.

Question 59

highly protein-bound drugs are ___ acting.

Answer 59

long

Question 60

plasma protein binding is a ______ (reversible, irreversible) process

Answer 60

reversible.

Question 61

irreversible binding of drugs can result in ____.

Answer 61

toxicity.

Question 62

give an example of an irreversible binding of a drug that results in toxicity

Answer 62

the irreversible binding of paracetamol metabolites to the hepatocytes.

Question 63

most drugs bind to which protein?

Answer 63

albumin

Question 64

what is the most abundant plasma protein

Answer 64

albumin

Question 65

what is the major source of drug and prolongs its action or cause local drug toxicity?

Answer 65

tissue reservoir

Question 66

give an example of a drug that concentrates in tissues and can give drug toxicity?

Answer 66

tetracyclins

Question 66

give an example of a drug that concentrates in tissues and can give drug toxicity?

Answer 66

tetracyclines

Question 67

the volume that would accommodate all the drug in the body if the concentration throughout was the same as in plasma

Answer 67

apparent volume of distribution (Vd)

Question 68

list the 3 compartments that take up the drug once it enters the body?

Answer 68

1- plasma compartment. 2- extracellular fluid. 3- total body water.

Question 69

list the 6 factors that Vd depends on?

Answer 69

1- lipid solubility. 2- plasma protein binding. 3- tissue sequestration. 4- pKa of the drug. 5- age, sex, obesity, pregnancy. 6- diseases like CHF, uremia, cirrhosis.

Question 70

drugs with ___ (high,low) of distribution are not easily removed by dialysis in case of poisoning

Answer 70

high

Question 71

Vd is expressed by?

Answer 71

Vd= dose administered I.V / plasma concertation.

Question 72

if a drug has a large Vd, most of the drug is in the _____ space and is unavailable to the ____ organs.

Answer 72

extraplasmic space. excretory,

Question 73

what does an extremely high Vd indicate?

Answer 73

that the drug is sequestered in some tissues.