3. Pharmacokinetics Introduction

Question 1

Pharmacokinetics (PK)

Answer 1

What the body does to the drug

Dose-concentration relationship

Absorption
Distribution
Metabolism
Excretion

Question 2

Pharmacodynamics (PD)

Answer 2

What the drug does to the body

Concentration-effect relationship

Question 3

Transfer of Drugs across cell membranes

Answer 3

Factors that affect a drugs movement and availability at sites of action:

Molecular size and structure- larger it is the harder it is to move into cell

Degree of ionization

Lipid solubility

Protein binding

Question 4

Passive Transport

Answer 4

Movement of a substance from an area of high concentration to an area of low concentration

Down concentration gradient - no energy required

Question 5

Active Transport

Answer 5

Movement from an areas of low concentration to an area of high concentration

Against concentration gradient- energy required

Question 6

Polarity of Drugs

Answer 6

Most drugs are weak acids and weak bases so exist in ionized and unionized forms

Nonpolar (unionized) - lipophilic

Polar (ionized) -hydrophilic

pH of surrounding area depends on how much of drug is ionized/unionized and will affect the drugs ability to cross the cell membrane