Pharmocokinetics and pharmocodynamics - Week 7

Pharmacokinetics

What body does to drug → movement of drug

Pharmacodynamics

What drug does to body → drugs effect on body

Absorption

Movement of the drug from administration site into bloodstream

Administration routes

• Oral (swallowing)

• Enteral (feeding tube)

• Sublingual (under tongue)

• Rectal

• Inhalation

• Intramuscular (injection)

• Transdermal (patch)

• Intravenous (IV)

Factors that affect absorption rate

• Slow blood flow → slow AR

• Food in digestive system → slow AR

• Surface area

Distribution

How the drug is spread throughout body

How does distribution work

• Leaves bloodstream through gaps in capillaries

• Binds to receptors on target cells

• Produces an effect

Metabolism

How the drug is broken down

First pass effect

1. Drug is swallowed

2. Travels through gastrointestinal tract

3. Large portion is broken down by liver

4. Remaining amount is eliminated

Excretion

How the drug leaves the body

Routes of excretion

• Excreted by kidneys

• Lost through sweat

• Lost through feaces

Drug half life

Time taken for plasma concentration to halve

Therapeutic range

Range of drug conc where drug has an optimal effect

How does drug make an effect

• Enters body

• Binds to receptors of cell

• Causes an effect

Why do drugs have side effects

Drugs bind to receptors in other tissues and other receptor types

Actions of drugs

Agonist = activates task
Antagonist = blocks task