L4 Pharmacokinetics I

Question 1

What are the 4 pharmacokinetic processes that make up “drug permeation”

Answer 1

“ADME!”

Absorption

Distribution

Metabolism

Elimination/Excretion

Question 2

How many half-lives does it take to reach steady state concentration?

Answer 2

5

Question 3

How many half lives does it take to eliminate the drug?

Answer 3

5

Question 4

What is the most common, convenient, safest and economical method of drug administration?

Answer 4

Oral/enteral/PO

Question 5

What is the first past effect?

Answer 5

Any drug taken orally is exposed to the liver first

Question 6

Are slow release formulations always regular?

Answer 6

No, often irregular and erratic

Question 7

What does parenteral mean

Answer 7

Non-oral

Question 8

What is the most direct route of administration?

Answer 8

Injections

Question 9

What route of administration is very rapid?

Answer 9

Inhalation

Question 10

Does rectally administered drugs undergo much first pass metabolism?

Answer 10

NO because distal anal canal is IVC route not portal

Question 11

Do buccal and sublingual drugs have a first pass effect?

Answer 11

Very little. It’s good for drugs that get degraded by first pass effect like nitroglycerin

Question 12

How does inflammation affect absorption through the skin

Answer 12

Increases absorption

Question 13

Drugs that have a high degree of lipid solubility are most likely absorbed by which mechanism?

Answer 13

Simple diffusion

Majority of drugs are lipid soluble when absorbed and water soluble when eliminated

Question 14

True or false:

Most drugs are either weak acids or weak bases

Answer 14

True

Question 15

In order to cross a membrane a drug must be: ionized or non-ionized?

Answer 15

NON-IONIZED

Question 16

Do drugs have to be lipid soluble to cross a membrane

Answer 16

YES

Question 17

Why can’t ionized drugs be absorbed?

Answer 17

They are surrounded by water molecules that increase its hydrophilic nature

Question 18

Can strong acids and bases be absorbed?

Answer 18

No

Question 19

The degree of _______ affects a drug’s ability to permeate biological membranes and exert its effect

Answer 19

Ionization

Question 20

An acid in an acidic environment is (ionized/nonionized) and (readily/not absorbed)

Answer 20

Non-ionized, readily

Question 21

A base in a basic environment is (ionized/nonionized) and (readily/not) absorbed

Answer 21

Nonionized, readily

Question 22

What is ion-trapping?

Answer 22

Acid in a basic environment or a base in an acidic environment

Question 23

Aspirin is a weak acid. Where will it be absorbed?

Answer 23

Stomach

H+ on aspirin won’t fall off in acidic environment. ASA remains non-ionized

Question 24

Pyrimethamine is a weak base. Where is it absorbed?

Answer 24

Intestine

Question 25

If you make urine basic, what kind of drugs will get trapped and excreted without affecting body?

Answer 25

Acidic drugs

Question 26

How do we make urine more basic?

Answer 26

Sodium bicarbonate

Acetazolamide

Question 27

If you acidify the urine, which drugs will be trapped and excreted?

Answer 27

Basic drugs

Question 28

How do we make the urine more acidic?

Answer 28

Ammonium chloride

Question 29

What is pKa

Answer 29

The pH at which the amount of ionized and non-ionized forms of a drug are equal

Question 30

If pH > pKa, which form of the drug dominates?

Answer 30

Unprotonated

Acid will be ionized (A-)
A base will be non-ionized (B)

Question 31

Which form of the base is ionized v non ionized:
B

BH+

Answer 31

B= non ionized

BH+=ionized

Question 32

Which form of the acid is ionized v non-ionized:
A-

HA

Answer 32

A- =ionized

HA= non ionized

Question 33

Can you tell if a drug is a weak acid or a weak base by looking at its pKa?

Answer 33

NOPE

Question 34

Amphetamine is a weak base with a pKa of 9.8. Would it be better absorbed in the stomach or the intestine?

Answer 34

It would be better absorbed in the intestine.

if pH

Question 35

Tylenol is a weak acid with a pKa of 9.5. Will it be better absorbed in the stomach or the intestine?

Answer 35

The stomach.

If ph

Question 36

What do you use the Henderson-Hasselbach equation for?

Answer 36

To figure out the ratio of A-:HA
Or B/BH+
If you’re given the pH of the environment and the pKa of the drug (as well as whether its a weak acid or base)

Question 37

What is the Henderson-hasselbach equation?

Answer 37

pH-pKa= log(A-/HA)

Or

pH-pKa= log(B/BH+)

Question 38

Drug A is a weak acid with a pKa of 6.4. What is the ratio of ionized to non-ionized drug in the urine with a pH=6.4

Answer 38

pH-pKa=log (A-/HA)

0=log(A-/HA)

(A-/HA) = 1

1:1 ratio

Question 39

Drug B is a weak acid pKa 6.4. What is the ratio of non-ionized to ionized drug in the blood with a pH=7.4

Answer 39

pH-pKa= log(A-/HA)

7.4-6.1=log (A-/HA)

1= log (A-/HA)

A-/HA=10:1
BUT the question asked non-ionized to ionized

1:10 is the ration of non-ionized to ionized

Question 40

Drug B is a weak base, pKa=5.4. What is the ratio of non-ionized to ionized drug in the blood with pH=7.4?

Answer 40

pH-pKa= log(B/BH+)

7.4-5.4=log(B/BH+)
(B/BH+)= 100:1

Question 41

What do we call “the amount of free and active unchanged drug that reaches systemic circulation?”

Answer 41

Bioavailability

Question 42

What is the bioavailability (F) of drugs administered intravenously?

Answer 42

100%

Question 43

If you knew the bioavailability of a drug and the effective oral dose (D oral) how would you calculate the equally effective IV dose (D iv)?

Answer 43

D iv= (D oral)(bioavailabilty/100)

D oral= (D iv)/(bioavailability/100)

Question 44

A drug has an oral bioavailabiligy of 40%. An effective oral dose is 100 mg. What is the equivalent IV dose?

Answer 44

D iv= (D oral)(bioavailability/100)

D iv= (100)(40/100)

D iv= 40 mg

Question 45

Effective IVdose is 100mg and bioavailability is 40%. What is the equivalent oral dose?

Answer 45

D oral= (D iv)/(Bioavailability/100)

D oral= (100)/(40/100)

          =100/.4

D oral =250mg