Pharmacokinetics and Pharmacodynamics

Question 1

Pharmacokinetics

Answer 1

What the body does to the drug

Question 2

Pharmacodynamics

Answer 2

What the drug does to the body

Question 3

Pharmacokinetic 4 stages

Answer 3

Absorption

Distribution

Metabolism

Excretion

Question 4

Why is it important to understand the differences between routes and formulations for administration?

Answer 4

Can affect how quickly and how much drug enters the systemic circulation

Question 5

Enteral Administration

Answer 5

Entry of drug through GI tract

(Rectal, tablets, capsules, caplets, liquids, sublingual, buccal)

Question 6

Parenteral Administration

Answer 6

“not by the GI tract”

Topical

Subq, IM, IV, inhalation,topical, transdermal

Question 7

First Pass Metabolism

Answer 7

Liver is the major site of drug metabolism

Can drop drug concentration dramatically

Note: some drugs are not metabolized

Question 8

Pharmacokinetics: ABSORPTION

Answer 8

Entry of drug into circulatory system (eg PO drug passing epithelial cell barrier of GI tract)

Absorption can be active or passive. (passive - movement of drug across GI wall down concentration gradient)

Most drugs absorbed passively

Question 9

Chemical factors affecting drug absorption

Answer 9

Drug size

Lipid solubility

Drug charge

Question 10

Physical factors affecting drug absorption

Answer 10

1. Blood flow to site of absorption (intestine blood flow higher than stomach)
2. Total surface area for absorption
3. Contact time
4. Drug formulation

Question 11

Absorption: Bioavailability

Answer 11

The proportion of drug that passes into systemic circulation after administration, taking into account absorption and local metabolic degradation

Often MUCH less than 100% if PO administration

Affected by first pass effect and drug absorption (solubility, stability, formulation)

Question 12

Pharmacokinetics: DISTRIBUTION

Answer 12

After absorption, drug is distributed through body

Average time for blood circulation is 1 minute (after absorption)

Tissues with high blood flow will be exposed to more drug, more quickly, than tissues with low blood flow
Rapid: heart, liver, kidney, brain
Slow: muscle, skin, fat

Question 13

Factors affecting drug distribution

Answer 13

Lean mass

Fat solubility of drug

Plasma protein binding

Question 14

Distribution: Plasma Protein Binding

Answer 14

Majority of drugs do not float around entirely free within blood

Drugs are often bound to plasma proteins such as albumin (major carrier of drugs)

Only free drugs can have effects. In liver disease, less albumin, thus MORE drug effect