Key Terms & Principles

Question 1

Define pharmodynamics

Answer 1

The effect of the DRUG on the body. These are the molecular interactions by which drugs exert their effects e.g.

• targets for drug action
• drug action at the target
• method of action production within a cell

Question 2

Define pharmacokinetics

Answer 2

The effect of the BODY does to a drug. This covers ADME (absorbtion, distribution, metabolism and excretion)

Question 3

What are the 2 main purposes of pharmacodynamics?

Answer 3

1. To determine dose range

2. To compare effectiveness and safety of one drug to another

Question 4

What is the main purpose of pharmacokinetics?

Answer 4

To design and optimise treatment regimes for individuals

Question 5

Name the bond types from weakest to strongest

Answer 5

Van der Waals< hydrogen bonds< ionic interactions

Question 6

Name the 4 main target proteins and explain their drug action at the target

Answer 6

1. Receptors: agonists activate the receptor while antagonists block the action of agonists
2. Ion Channels:either block or modulate the opening/ closing along membrane for selective ion passage
3. Enzymes: either inhibit or act as false substrate
4. Carriers: either transported in the place of the endogenous substrate or inhibit transport of ions and small organic molecules

Question 7

Define an agonist and provide an example

Answer 7

An agonist is a ligand that combines with receptors to elicit a cellular response e.g. Histamines
- they act as an agonist at the H1 receptor in the smooth muscle to increase blood flow

Question 8

Define an antagonist and provide an example

Answer 8

An antagonist is a drug that blocks the response to an agonist e.g. Terfenadine
-Acts at the H1 receptor in the smooth muscle to decrease local blood flow

Question 9

Name and explain the 4 receptor signal types

Answer 9

1. LIGAND GATED: are channel linked receptors that need an agonist to open the channel e.g. nicotinic ACh receptor
2. VOLTAGE GATED; are not linked to receptors but require a change in electrical charge across membrane to open/close e.g. Na+ channels in nerve cell membranes
3. G PROTEIN COUPLED: largest family of receptors, formed of 7 transmembrane helicases and 3 subunits (alpha, beta,gamma). The alpha subunit varies between receptors;
   - Gs (stimilatory), Gi (inhibtory) n Go (activates phospholipase C)
4. KINASE LINKED: large extracellular ligand binding domain connected to intracellular domain by a single helix

Question 10

What are the 2 major classes of nuclear receptors?

Answer 10

Class I- located in cytoplasm, form homodimers & ligands are endocrine (steroids, hormones)

Class II- present in nucleus, form heterodimers, ligands are lipid (fatty acids, metabolism)

Question 11

Where do endogenous products normally bind?

Answer 11

The orthosteric site, where processes can be turned on and off

Question 12

What is the difference between a GRADED and a QUANTAL dose-response curve?

Answer 12

Graded usually reflects the response of a particular system (INDIVIDUAL)

Quantal usually reflects drug doses and used for population based research

Question 13

Why do we use dose-response curves?

Answer 13

• They allow the estimation of Emax which is used to deduce drug EFFICACY
• They allow estimation of concentration/ dose required to produce 50% of maximal dose (EC50), to calculate POTENCY

Question 14

What can be used to identify unknown receptors?

Answer 14

Kd, the equilibrium dissociation constant. It can be used to quantitatively compare the affinity of different drugs on the same receptor. The lower the Kd value, the greater the affinity and the less drug required

Question 15

What factors can affect potency?

Answer 15

Potency is how much of a drug is needed to bind to create the desired effect. It is dependent on:
- drug affinity
- drug efficacy
- receptor density
The lower the EC50 value, the greater the potency