Pharmacokinetics

Question 1

What is pharmacokinetics?

Answer 1

how drugs move through your body

Question 2

What is pharmacodynamics?

Answer 2

how drugs affect its target to produce the desired physiological effects

Question 3

What is the life of a drug molecule in the human body?

Answer 3

Absorption- how does the drugs get into the body

Distribution (to target) - how does the drug get to the target site

Metabolism- how is the molecule chemically altered in the body

Clearance- how it is removed from the body

Question 4

What is the first step of absorption?

Answer 4

Drugs must pass through epithelial and endothelial cell layers, likely several

Question 5

What charged state must drugs be in to pass through the plasma membrane?

Answer 5

The drugs must be hydrophobic (which is NEUTRALLY charged) to pass through the cell since the plasma membrane very hydrophobic

Question 6

What is simple diffusion and what type of cells are able to undergo it?

Answer 6

molecules moving down their gradient without additional help.

Hydrophobic drugs are able to do this

Question 7

Which forms of drug absorption are saturable and non-saturable?

Answer 7

Simple diffusion is not saturable- meaning it is not dependent on presence of any other transport protein

-only on concentration of drug

Facilitated diffusion and active transport are SATURABLE

Question 8

What types of drug absorption are faster at lower concentrations?

Answer 8

Facilitated diffusion and active transport

Question 9

What is pKA and what does it tell you?

Answer 9

pKA is the pH at which a molecule is 50% split between hydrophilic and hydrophobic forms.

Question 10

How does a weak base behave in high and low ph environments? A weak acid?

Answer 10

For weak acids

at low pH: hydrophobic and charged
high pH: hydrophobillic and uncharged

For weak bases

At low pH: hydrophilic and charged
At high pH: hydrophobic and uncharged

Question 11

How does a weak base behave in high and low ph environments? A weak acid?

Answer 11

For weak acids

at low pH: hydrophobic and uncharged (H+ attached)
high pH: hydrophilic and charged (H+ leaves)

For weak bases

At low pH: hydrophilic and charged (H+ binds to base, forming positive ion)

At high pH: hydrophobic and uncharged (no H+ present, neutral state)

Question 12

What is the Henderson- Hasselbach equation for weak acids?

What is it for weak bases?

Answer 12

For acids-

[A-]/[AH]= 10^ (pH-pKa)]

[B]/[BH+]= 10^(pH-pKA)

Question 13

What does the Henderson- Hasselbach equation solve for for weak acids?

What is it for weak bases?

Answer 13

For acids-

[A-]/[AH]= 10^ (pH-pKa)]
-AH is absorbable

[B]/[BH+]= 10^(pH-pKA)
-B is absorbable

Question 14

How does pH compare to pka for weak acids and weak bases

Answer 14

For weak acids, when is less than pKA it is more neutral molecule

For weak bases, when pH is greater than pKa, molecule is more neutral

Question 15

Define pH trapping?

Answer 15

Ex) Aspirin molecules in stomach (pH) are 99% in their hydrophobic (AH) absorbable form:

They can the diffuse into the plasma

Because plasma has a much higher pH, it will drive aspirin into its hydrophilic for (A-, in a huge proportion)

A- cannot cross back over into the stomach area again so it is trapped

Question 16

Explain the reasons for the high levels of weak base drugs in lysosomes:

Answer 16

As drugs are converted from their charged to uncharged form, they are capable of entering cellular and lysosomal compartments, but not exiting (the inside of the cell is more acidic than the outside)

Question 17

What is bioavailability?

Answer 17

What fraction of drug makes it into circulatory system ( after the drugs have completed the first pass (through liver and through cytochome p45)

(IV administration will be 100%)

Question 18

What is the equation for bioavailability and what how do you calculate it?

Answer 18

Bioavailability= AUC (oral)/AUC (IV)= 1 mg-hour/L divided by 3 mg hour/L= % by the oral route of administration

Question 19

What does Area Under Curve represent?

Answer 19

a measure of total drug exposure

Question 20

What is the equation to calculate for Volume of Distribution?

Answer 20

Vd= Q/Cp

Q=mg of drug
Cp= Plasma coc

Question 21

Name 3 things that a high Vd indicates about a drug:

Answer 21

• It is actively moved out of the plasma
• tissue binding
• ph trapped

Question 22

What type of drugs typically have a Vd greater than the total?

Answer 22

Lipophilic drugs

Question 23

Where in the body will lipophilic drugs, like propophol, is moved out of the plasma?

Answer 23

Propophol is an extremely hydrophobic and redistributes quickly to other hydrophobic tissue

Brain, skeletal muscle, finally ends up in adipose tissue

Question 24

How two physical bodily aspects need to me taken into account with drug administration?

Answer 24

Body fat content and age