Pharmacodynamics

Question 1

What is Pharmacodynamics?

Answer 1

• The science where drugs exert an effect on the body.

- What the drug does to the body.

Question 2

What are Receptors?

Answer 2

Molecules that exist on cells. Usually proteins but can be lipids or CHO.

Question 3

What are Agonist Drugs?

Answer 3

Has an effect at a receptor.

Question 4

What are Antagonist Drugs?

Answer 4

Blocks a receptor effect.

Question 5

What is a Ligand?

Answer 5

Any molecule that binds to a receptor.

Question 6

What does Endogenous mean?

Answer 6

Produced by the body

Question 7

What does Exogenous mean?

Answer 7

Anything not produced by the body; drugs.

Question 8

What is a Partial Agonist/Antagonist?

Answer 8

Some drugs mimic the natural response but to a lesser extent. Some drugs do not fit exactly but still form enough bonds to initiate a partial response. Partial fit = partial agonist or antagonist.

Question 9

What is the Lock and Key Theory?

Answer 9

Receptor/Ligand interaction
Receptor = Lock
Ligand = Key

Question 10

What are the Characteristics of Receptors?

Answer 10

• Made of proteins.
• Can be internal or external to cells.
• Natural exist within body to transmit messages (e.g. Nerve Terminals).
• Name for the Ligand that act on them.
• Often Contain Subtypes - Bind the same ligands, but different effects/distributions and structure (e.g. B1 and B2).
• Drugs can be designed to act on one subtype but not others (e.g. B-Blockers, B-Adrenoreceptor specific vs. non-specific)

Question 11

What is Specificity?

Answer 11

Refers to how specific drugs are for a particular receptor or receptor subtype. Drugs effects are more targeted so less side effects. Drugs with differing specific effects in pathways can be used together for synergistic benefit (e.g analgesics).
.

Question 12

What is Affinity?

Answer 12

The degree of attraction that a chemical (drug) has for a receptor. High affinity means the drug is strongly attracted to the receptor. This means that less drug needed. Drugs with a high affinity can displace other drugs and substances off the receptor. Drugs with a low affinity for a receptor are easily displaced by other drugs or the endogenous ligand.

Question 13

What is Efficacy?

Answer 13

Refers to the ability of the drug to produce a reaction at a receptor site.

Question 14

What is Potency?

Answer 14

Refers to the amount of drug required to produce a reaction at a receptor site.

Question 15

What is Synergistic?

Answer 15

Used especially of drugs or muscles that work together so the total effect is greater than the sum of the two (or more).

Question 16

What is a Competitive Drug (Reversible Reaction)?

Answer 16

Drug compete with endogenous (body’s own) substrate. There is competition between drug and endogenous ligand for binding to receptor. Both Drugs can’t bind at the same time. In sufficient quantities, the unbound drug can displace the bond drug from the receptor. Affinity is considered then. If the bound drug has a high affinity for the receptor, then it will take more of the unbound drug to displace it.

Question 17

What is a Non-Competitive Drug (Irreversible reaction)?

Answer 17

Bind irreversibly to a receptor so other substances can’t bind on. Once the drug is bound on, the receptor becomes inactivated, and can not be restored. Another action potential can be created when a new receptor replaces the old.

Question 18

What is Receptor Up Regulation?

Answer 18

Occurs in prolonged antagonist activity. Either an increase in receptor number or receptors move closer to cell surface (temporary effect). A problem if antagonist is abruptly withdrawn as endogenous agonist has a sudden increased effect

Question 19

What is Receptor Down Regulation?

Answer 19

Decreased number or sensitivity of receptors to drug (e.g. opioids). Caused by chronic exposure/ ageing /disease. Need increasingly higher doses to have an effect.

Question 20

What is Drug Tolerance?

Answer 20

Decreasing pharmacological activity for same dose. Can occur when drug administered over a prolonged period. Effect reversible once drug discontinued. Occurs with some drugs but not others e.g. morphine but not tramadol. Due to combination of :

• Up or down regulation of receptors
• Enzyme induction (metabolism changes)

Question 21

What are Parmacodynamic Interactions?

Answer 21

Occurs when the mechanism of action of one drug affects the mechanism of action of another drug. Non steroidal anti-inflammatory drugs and diuretics. Warfarin and aspirin on clotting time.