Pharmacology General Principles Part II

Question 1

Elimination

Answer 1

The process of making a drug pharmacologically inactive and removing it from the body

Includes metabolism and excretion

Question 2

Is free drug or plasma protein bound drug filtered from the body?

Answer 2

Only free drug is filtered from the body while plasma protein bound drug remains in the body

Question 3

Excretion formula

Answer 3

Excretion = Filtration - Reabsorption + Secretion

Question 4

What is creatine clearance used to determine?

Answer 4

An approximate measure of renal function

Question 5

If excretion = GFR

Answer 5

There is no absorption or secretion

Question 6

If excretion < GFR

Answer 6

There is reabsorption

Question 7

If excretion > GFR

Answer 7

There is secretion

Question 8

Clearance mechanisms

Answer 8

Metabolism and Excretion are both clearance mechanisms

Question 9

Clearance (CL) formula

Answer 9

Question 10

Distribution phase of IV drug (graph)

Answer 10

Question 11

Half life formula

Answer 11

Question 12

How many half lifes for a drug to be eliminated from the body?

Answer 12

5 half-lifes which equals 95% of the drug removed from the body

Question 13

Do most drugs follow first-order or zero-order kinetics?

Answer 13

~95% of drugs follow first-order kinetics

Question 14

What are some common drugs that follow zero-order kinetics?

Answer 14

• Aspirin
• Ethanol
• Phenytoin

Question 15

First-order elimination kinetics

Answer 15

• Elimination rate is diretcly proportional to the drug concentration
• Half-life is fixed

Question 16

Zero-order elimination kinetics

Answer 16

• Rate of elimination is independent of drug concentration and occurs at a constant rate
• No half-life

Question 17

Steady-state plasma drug concentration (C_p(ss))

Answer 17

When the rate of drug administration = rate of drug elmination

Purpose is to maintain a therapeutic dose

Question 18

How many half lifes of the drug does it take to reach the steady-state plasma drug concentration?

Answer 18

It takes 1 half-life to reach 50% of the CP(ss)

And 5-6 half-lives tp reach 100% of the CP(ss)

Question 19

Loading dose formula

Answer 19

Question 20

When would we use a loading dose?

Answer 20

When it is necessary to achieve the therapeutic plasma concentration levels quickly

Question 21

Maintenance dose and dosing rate forumula

Answer 21

Question 22

Efficacy

Answer 22

Greatest effect an agonist can produce if the dose is taken to the highest tolerated level

Question 23

Potency

Answer 23

• Amount of drug needed to produce a certain effect
• Affected by the affinity of the receptor for the ddrug and the number of receptors available

Question 24

EC₅₀/ED₅₀

Answer 24

The concentration/dose of a drug required to produce a response in 50% of individuals

Question 25

Efficacy and Potency chart

Answer 25

Question 26

TD₅₀

Answer 26

Dose required to produce toxicity in 50% of individuals

Question 27

LD₅₀

Answer 27

Dose required to produce a lethal response in 50% of individuals

Question 28

Therapeutic index

Answer 28

TD50/ED50

Not a very goodd estimate of safety

Question 29

Therapeutic Window

Answer 29

TD1/ED50

Range between ED50 and starting point of TD50 (which is TD1)

Range of drug dosages which can effectively treat the disease while staying with the safety range

Question 30

Certain safety factor

Answer 30

TD1/ED99

Dose that produces minimum toxicity (toxicity in 1% of individuals)

And is effective in 99% of individuals

Question 31

Agonist

Answer 31

Drug that binds to the drug-receptor and activates it

Question 32

Partial agonist

Answer 32

Activates the receptor but does not produce the maximal response

Question 33

Full agonist

Answer 33

Activates the receptor and produces the maximal response

Question 34

Inverse agonist

Answer 34

Binds to the inactive state of the receptor and decreases the constitutive activity

Produces the opposite effect of the agonist

Question 35

Competitive antagonists

Answer 35

Binds to the agonist receptor site in a reversible way without activating the effector system of that receptor

Question 36

Non-competitive antagonists

Answer 36

Irreversible binding to the active site

or

Irreversible or reversible binding to the allosteric site

In either case, agonist cannot out compete the non-competitive antagonist