Principles of Drug Therapy

Question 1

Define pharmacokinetics.

Answer 1

What the body does to the drug.

Question 2

Define pharmacodynamics.

Answer 2

What the drug does to the body.

Question 3

What’s the difference between pharmacokinetics and pharmacodynamics?

Answer 3

Pharmacokinetics refers to what the body does to the drug, whereas pharmacodynamics describes what the drug does to the body.

Question 4

What are the four pharmacokinetic properties? What do they determine?

Answer 4

The four properties determine the speed of onset of drug action, the intensity of the drug’s effect, and the duration of the drug action. These include:

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

Question 5

What are the different routes of administration for a drug?

Answer 5

1. Enteral
   
   • Oral
   • Sublingual
2. Parenteral
   
   • Intravenous (IV)
   • Intramuscular (IM)
   • Subcutaneous (SC)
3. Other
   
   • ​​Oral and nasal inhalation
   • Intrathecal (injectoion into spinal canal, or subarachnoid space )/Intraventricular
   • Topical
   • Transdermal
   • Rectal​​

Question 6

What are the different mechanisms in which a drug can be absorbed?

Answer 6

1. Passive diffusion (most drugs)
2. Facilitated diffusion
3. Active transport (drugs resembling natural molecules)
4. Endocytosis/exocytosis (large-compound drugs)

Question 7

What factors affect the efficiency of absorption?

Answer 7

• pH
• Blood flow to target site
• Target area volume
• Contact time at absorption site
• P-glycoprotein expression

Question 8

What different factors affect the distribution of a drug?

Answer 8

1. Blood flow
2. Capillary permeability
3. Binding plasma proteins and tissues
4. Volume of distribution