Pharmacodynamics

Question 1

What are some ways drugs can have effects on the body?

Answer 1

• Acting on receptors
• Inhibiting carriers (transporters that move 1 or more ions across a membrane)
• Modulating or blocking ion channels
• Upregulating/inhibiting enzymes

Question 2

Describe ligand gated ion channel receptors.

Answer 2

• Located on membrane
• Ligand binds to receptor causing ions to pass through channel
• Takes milliseconds to cause response
• EXAMPLE: Nicotinic ACh receptors

Question 3

Describe GPCRs

Answer 3

• Located on membrane
• Take seconds to cause a response
• Use an α subunit which activates and inhibits enzymes through biochemical cascades

Question 4

What are the 3 types of GPCRs?

Answer 4

• Gαs - activate adenylate cyclase
• Gαq - activate phospholipase C
• Gαi - inhibit adenylate cyclase

Question 5

What is the difference between affinity and potency of a drug?

Answer 5

• AFFINITY - How strongly ligand binds to receptor
• POTENCY - Amount of drug required to cause an effect

Question 6

What do the following terms mean
- EC50
- Emax

Answer 6

• EC50 - Agonist concentration to elicit a half maximal response
• Emax - Maximal response of drug

Question 7

Outline the difference between a competitive and non-competitive antagonist.

Answer 7

• COMPETITIVE - reversible binding to active site of receptor
• NON-COMPETITIVE - binds to allosteric site and prevents receptor activation. Response won’t be maximal

Question 8

What do the following terms mean
- ED50
- TD50

Answer 8

• ED50 - Drug concentration to achieve therapeutic effect in 50% of population
• TD50 - Drug concentration to cause toxic effects in 50% of population