Exam 1, Ch. 3 review

Question 1

List the pharmacokinetic variables (ADME)

Answer 1

Absorption, Distribution, Metabolism, excretion

Question 2

Describe the four ways a drug gets across barriers.

Answer 2

Aqueous diffusion, Lipid diffusion, Special carriers, Endocytosis and exocytosis

Question 3

Define Volume of distribution (Vd)

Answer 3

Space available in body to contain drug

Question 4

Define Clearance (CL)

Answer 4

Ability of body to eliminate drug (NOT elimination)
- Predicts ROE

Question 5

Clearance and ROE - First-order elimination

Answer 5

Most drugs, clearance is CONSTANT, ROE varies.

Question 6

Clearance and ROE - Zero order elimination

Answer 6

Occurs when bodys ability to eliminate a drug has reached its maximum capacity. e.g. all transporters are being used, can only clear at its maximum rate.

ROE is constant, and clearance varies with concentration.

Question 7

Concentration (C)

Answer 7

How much of the drug is in the body?

Question 8

Rate of elimination (ROE)

Answer 8

CL x C
-Varies with concentration

Question 9

Target Concentration (TC)

Answer 9

Concentration that will produce desired effect

Question 10

Half-life (T1/2)

Answer 10

Time required to change drug in body to 1/2 concentration.

Question 11

Bioavailability (F)

Answer 11

Fraction of unchanged drug reaching systemic circulation

Question 12

Relate Vd and CL to drugs (what is meant by a high Vd? a high CL?)

Answer 12

A high Vd means that a large portion of the drug is leaving the bloodstream and distributing into tissues, they tend to be lipophiic in nature, may accumulate in fat. This can be a longer half life and slower removal from body.

A high CL means the drug is eliminated by the body rapidly.

In total, High Vd and low CL means it will last a long time and can be a potent drug. Low Vd and low CL will require frequent dosing.

Question 13

Define capacity limited elimination and the variables in the equation

Answer 13

Zero-order elimination, the body can only get rid of the drug so fast, its going as fast as possible and its clearance amount will be the same every hour until it gets below limited elimination.

-non-linear
-Starts as zero order, turns into 1st order once drug is cleared enough.

Question 14

Analyze flow dependent elimination as it relates to extraction ratio.

Answer 14

Depends on blood flow through the organ.

blood flow (x) extraction ratio = organ clearance.

Q is the flow of blood.
drug into organ -> drug out of organ = What % of drug came out?

Question 15

IF blood flow is low, but extraction ratio is high, what’s the clearance?

Answer 15

Low.

Clearance is ONLY high (normal) if both ER and blood flow is high.

Question 16

Estimate the half-life of a drug based on its clearance and volume of distribution.

Answer 16

use the half life formula, which is 0.7 x Vd divided by CL

Question 17

Describe the blood level versus time for drugs subject to zero-order elimination and for
drugs subject to first-order elimination. What remains constant (CL, or ROE)?

Answer 17

In first order elimination, clearance remains constant. It clears the same amount of drug every hour.. In zero-order elimination, it clears at the same ROE every hour until the concentration is low enough to move to first-order.

Question 18

List 7 routes of drug administration.

Answer 18

IV, IM, Subcutaneous, transdermal, oral, rectal, sublingual, inhalation.

Question 19

Calculate half-life, loading and maintenance dosage regimens for oral or intravenous
administration of a drug when given the following information: target concentration,
oral bioavailability, clearance, and volume of distribution.

Answer 19

PRACTICE QUESTIONS GIVEN! DO THEM!

Question 20

Calculate the dosage adjustment required for patients who are not 70 kg

Answer 20

IF DRUG DOES NOT PENETRATE FAT, USE:
ideal body weight for obese people, which is:

men = 52 + (1.9kg x inches over 60in)

women = 49 + (1.7kg x inches over 60in)

Question 21

Describe Therapeutic Drug Monitoring (Peak and trough).

Answer 21

Peak: drawn 5-10 minutes after IV drug admin

Trough: 30 minutes prior to next dose of the drug. This all helps assess individual responses in comparison to standard population.

Specifically used in digoxin and theophylline

most important thing affecting this is clearance

Question 22

List the test used to determine kidney function.

Answer 22

Creatinine clearance. Muscles produce creatinine and kidneys clear them, telling us how well kidneys are functioning.