General Principles of Drug Action

Question 1

Pharmacodynamics

Answer 1

what a drug does to the body (biological effects and mechanism of action)

Question 2

Pharmacokinetics

Answer 2

what the body does to a drug (absorption, distribution, metabolism and excretion of drugs and their metabolites)

Question 3

A Drug is

Answer 3

any single synthetic, or natural, substance of known structure used in the treatment, prevention, or diagnosis of disease; including everyday substances (eg. caffeine, nicotine, ethyl alcohol) and illicit substances (eg. cannabis, heroin, cocaine)

Question 4

A Medicine is

Answer 4

a chemical preparation containing one or more drugs used with the intention of causing a therapeutic effect. Usually contain agents additional to the active drug.

Question 5

Selectivity

Answer 5

is the ability of a drug to distinguish between different molecular targets within the body (this depends upon the dose). Allows drugs to interact with select cells and tissues to produce their intended effect by binding to particular molecular targets that they express.

Question 6

Selective targets may include

Answer 6

those unique to invaders such as bacteria, viruses, fungi and parasites. (eg. penicillins)

Question 7

Drugs Act by

Answer 7

binding to regulatory proteins (mainly enzymes, carrier molecules, ion channels, receptors) to modify their function.

Question 8

Receptors

Answer 8

are macromolecules on, or within, cells that mediate the biological actions of hormones, neurotransmitters and other endogenous substances.

Question 9

Agonist

Answer 9

a drug that binds to a receptor to produce a cellular response

Question 10

Antagonist

Answer 10

a drug that reduces, or blocks, the actions of an agonist by binding to the same receptor. Possess affinity but lack efficacy.

Question 11

Affinity is

Answer 11

Strength of association between ligand and receptor. Determined by chemical bonds between a ligand and its receptor

Question 12

Efficacy is

Answer 12

the ability of an agonist to evoke a cellular response

Question 13

Ability of a drug to distinguish between different molecular targets within the body

Answer 13

critically dependent upon the dose of the drug and frequently the way in which it is administered.

Question 14

Targets

Answer 14

drugs are not specific - have more than one potential target and therefor selective

Question 15

agonist concentration and receptor occupancy relationship

Answer 15

as agonist concentration increases the fraction of receptors within a population that are occupied by agonists increases. Linear hyperbolic relationship. Sigmoidal semi-logarithmic relationship.

Question 16

EC50

Answer 16

is the concentration of agonist that elicits a half maximal effect

Question 17

Reversible Competitive Antagonism

Answer 17

binding of agonist and antagonist, both of which are reversible, occur at the same (orthosteric) site and is thus competitive and mutually exclusive. Can be overcome by increasing the concentration of agonist.

Question 18

Non-Competitive Antagonism

Answer 18

Agonist binds to the orthosteric site and antagonist binds to a separate allosteric site (therefore non-competitive). Both may occupy the receptor reversibly and simultaneously, but activation cannot occur when antagonist is bound

Question 19

Partial agonists

Answer 19

have a lower efficacy than full agonists