ADME1 - Tavalin

Question 1

Describe the processes that shape the time course of drugs within the body.

Answer 1

dynamics of drug absorption, distribution, metabolism and excretion.

Question 2

Explain the mechanisms of drug passage across biological membranes

Answer 2

Passive diffusion - governed by Fick’s law, Rate = DAK(Cout - Cin)/dX, where A = surface area, K =partition coef, D = diffusion coef.

Carrier-mediated biotransport:

Question 3

How does local pH and drug pKa affect the passage of weak electrolyte drugs across membranes?

Answer 3

Drugs are absorbed only when they are non-ionized, when they are more lipid-soluble. Most drugs are weak electrolytes

Question 4

Describe the concept of bioavailability

Answer 4

?

Question 5

List the routes of drug administration and the pattern of drug distribution of each.

Answer 5

?

Question 6

What is apparent volume of distribution?

Answer 6

?

Question 7

What is the therapeutic index?

Answer 7

Therapeutic index = MTC/MEC

maximum toxic conc. / min effective conc.

Question 8

Which type of drug will more likely be able to pass through a cell membrane: polar or nonpolar?

Answer 8

nonpolar

Question 9

What is the therapeutic index?

Answer 9

Ratio of Maximum Tolerable concentration: Minimum effective concentration.
Small therapeutic index means a risky drug because the room for error is smaller.

Question 10

What is Fick’s law?

Answer 10

a law describing the diffusion of solute acros a membrane

Question 11

Can carrier-mediated biotransport go against the gradient?

Answer 11

No. It flows down the concentration gradient. Only active transport can move something against the gradient.

Question 12

What is pinocytosis?

Answer 12

When something is taken up into a cell membragne via invaginations (endocytosis). It is another method that drugs get across membranes.

Question 13

What is the henderson hasselbach equation?

Answer 13

pH = pk + log [A]/[HA]
pH = pk + log[B]/[BH]

Question 14

Will basic drugs pass from stomach to plasma well?

Answer 14

No, stomach has a pH around 1.4 and basic drugs will be ionized to their BH+ form, making them polar and charged.

Question 15

Will acidic drugs cross the stomach to plasma barrier well?

Answer 15

yes. The stomach is very acidic and acidic drugs have low pKa’s so they will remain in their HA form which is neutral compared to the A- form.

Question 16

What does a bioavailability of 0.7 mean?

Answer 16

70% of drug is bioavailable.

Question 17

What is the bioavailability of IV drugs?

Answer 17

1 because it is immediately in blood stream in its active form.

Question 18

What is enteral?

Answer 18

any method involving GI tract: oral ingestion, sublingaual or rectal.

Question 19

What is parenteral?

Answer 19

Any method besides the GI tract.

IV, subcu, intramusc, introarterial, inhale, topical

Question 20

What are the advantages of oral ingestion? Disadvantages?

Answer 20

safe, cheap.

Slow onset, patient compliance, low bioavailability.

Question 21

Would increasing the rate of gastric emptying increase or decrease drug absorption?

Answer 21

Counter-intuitive: Because the stomach has a smaller surface area than the intestines, you want the stomach to empty quickly so the drug has more time to be absorbed in the instestinal tract. Drug absorption will increase as stomach time decreases.

Question 22

What are the advantages of sublingual? Disadvantages?

Answer 22

bypasses first pass, higher bioavailability, drug stability due to neutral pH, rapid absorption.
Holding dose in mouth is inconvenient, only useful when drug dosage is small.

Question 23

What are the advantages of rectal administration?

Answer 23

useful in children, unconscious or vomiting patients, bypasses first pass metabolism.
Absorption is erratic and the thought of shoving something up your ass is not very enticing