Pharmacokinetics

Question 1

4 processes that govern pharmacokinetic principles

Answer 1

1. Absorption
2. Metabolism
3. Distribution
4. Elimination

Question 2

Which drug form more readily crosses membranes?

Answer 2

Non-ionized form

Question 3

Which form of acid is non-ionized?

Answer 3

Protonated form (HA)

Question 4

Which form of base is non-ionized?

Answer 4

Deprotonated form (B)

Question 5

What is the pKa?

Answer 5

The pH at which 50% of the drug is ionized and 50% is non-ionized

Question 6

What is the Henderson-Hasselbach equation?

Answer 6

log (protonated form/unprotonated form) = pKa - pH

Question 7

Which form predominates if pH

Answer 7

Protonated form predominates

Question 8

Which form predominates if pH > pKa?

Answer 8

Unprotonated form predominates

Question 9

Where are weak acids and weak bases more readily absorbed?

Answer 9

Weak acids –> stomach

Weak bases –> intestines

Question 10

Cardiovascular factors that affect drug distribution

Answer 10

1. Cardiac output
2. Regional blood flow
3. Capillary permeability
4. Binding to plasma proteins

Question 11

Non-cardiovascular factors that affect drug distribution (3)

Answer 11

1. Preferential tissue binding
2. Drug molecule size
3. Lipid solubility

Question 12

Ultimate goal of biotransformation

Answer 12

Make compound more water soluble and therefore able to be eliminated from the body

Question 13

Phase I biotransformation purpose

Answer 13

Generate a more polar molecule by exposing a functional group on the parent compound

Question 14

Phase II biotransformation purpose

Answer 14

Reactions yield a more water soluble conjugated produce to be excreted

Question 15

3 common phase I biotransformation reactions are mediated by which enzymes?

Answer 15

1. Oxidation, reduction, and hydrolysis

2. Cytochrome P450s

Question 16

3 most common phase II biotransformation reactions

Answer 16

1. Glucuronidation
2. Sulfation
3. Acetylation

Question 17

4 less common phase II biotransformation reactions

Answer 17

1. Glutathione conjugation
2. Glycine conjugation
3. Methylation
4. Water conjugation

Question 18

Volume of distribution

Answer 18

V= Amount of drug in body/ concentration of drug in blood or plasma

Question 19

Clearance

Answer 19

Rate of elimination / Concentration of drug (ml/min/kg)

Question 20

Zero- order elimination

Answer 20

Specified amount of drug is eliminated over a period of time and is independent of drug concentration
The elimination process is saturated

Question 21

First-order elimination

Answer 21

Fraction of drug eliminated is constant

Not dependent on drug concentration

Question 22

Capacity-limited elimination

Answer 22

Concentration of the drug has saturated the elimination capabilities
Mimics zero-order kinetics
**Important for continuous dosing

Question 23

Flow-dependent Elimination

Answer 23

Limiting factor for elimination of a drug is the blood flow to the metabolizing organ. The greater the flow, the greater the extent of elimination

Question 24

Half Life

Answer 24

T(1/2) = 0.693 x V / CL

Question 25

Using a semi-log plot, which compartment model shows an accurate initial plasma concentration at time zero? Which compartment model shows an inaccurate one?

Answer 25

1. One compartment model shows an accurate initial plasma concentration
2. Two-compartment model shows an inaccurate initial plasma concentration if extrapolated on a linear line

Question 26

Accumulation Factor equation

Answer 26

AF = 1 / Fraction lost in one dosing interval