Introduction To Drug Action

Question 1

Pharmacokinetics

Answer 1

What the body does to a drug

Question 2

Medicine definition:

Answer 2

Treatment plan containing one or more drugs for a therapeutic effect

Question 3

Selectivity:

Answer 3

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

Question 4

What is an agonist?

Answer 4

Drug that binds to a receptor to produce a cellular response

Temporarily activate receptors by producing a conformational change

Possess affinity and efficacy

Question 5

Affinity and efficacy:

Answer 5

Affinity: Strength of association between ligand and receptor (binding)

Efficacy: Ability of an agonist to evoke a cellular response (activation)

Question 6

What is an antagonist?

Answer 6

Drug that reduces, or blocks, the actions of an agonist by binding to the same receptor – do not activate them

Possess affinity but lack efficacy

Question 7

Potency and efficiency:

Answer 7

Potency: Amount of drug required to produce a desired effect

Efficacy: Maximum response achievable from drug

Question 8

EC50

Answer 8

Concentration of agonist that elicits half maximal effect

Easy to see using semi-logarithmic plot of concentration vs. effect - sigmoidal relationship

Question 9

Competitive antagonism:

Answer 9

Binding of agonist and antagonist occur at same (orthosteric) site - competitive

Cause parallel right shift of agonist concentration response curve with no depression in maximal response

Question 10

Non-competitive antagonism:

Answer 10

Agonist binds to normal site and antagonist binds to separate (allosteric) site - not competitive

Both may occupy sites simultaneously, but activation cannot occur when antagonist is bound

Depress the slope and maximum response curve, but do not cause a rightwards shift

Question 11

Partial agonist

Answer 11

An agonist that cannot elicit as large an effect (even with 100% receptor occupancy) as another agonist acting through the same receptors in the same tissue

Question 12

How can KA affect the affinity a ligand has for its receptor?

Answer 12

The lower the KA the greater the affinity the ligand has for the receptor

Question 13

What is KA?

Answer 13

The association constant

The rate at which one molecule binds to another to form a complex

Question 14

Potency

Answer 14

The concentration or amount needed to produce a desired effect

The lower the EC50 the greater the potency

On graph:
- Steep gradient
- Reaches maximum effect

Question 15

How do non-opioid drugs (e.g. ibuprofen) cause pain relief?

Answer 15

By being an antagonist to COX1 and COX 2 enzymes (these enzymes produce prostaglandins which cause pain)

Question 16

What drug would you prescribe as a beta blocker to a patient who doesn’t have asthma?

Answer 16

Propranolol