Pharmacodynamics

Question 1

Pharmacodynamics

Answer 1

What Meds do to the Body

• Most drugs bind to cell receptors where they initiate reactions that alter cell’s physiology
• Some of a drug’s molecules will find target cell, some distributed, metabolized, and excreted
• Drugs exert primary action at cell level

Question 2

Medication Actions

Answer 2

Pharmacology at

cell level, organism level, and population level

Question 3

Drug Receptors

Answer 3

• Proteins/Glycoproteins on cell surface, organelle inside cell, or cytoplasm
• Finite mumber - response plateaud once saturated
• Downregulation/Upregulation

Question 4

What happens after a drug is bound to the receptor?

Answer 4

• Ion channel opens/closes
• Activate biochemical messengers, second messengers (cAMP, cGMP, C++, Inositol Phosphates) - each signal that passes amplified
• Inhibit/Initiate normal cell function
• Steroids move right into cell w/o help

Question 5

What is Affinity

Answer 5

Strength of binding b/t drug and receptor

Question 6

Dissociation Constant (K_p)

Answer 6

Measure of a drug’s affinity for a given receptor.

The concentration of a drug needed for 50% receptor occupancy

Question 7

What is an Agonist

Answer 7

Drugs that alter physiology of a cell by binding to plasma membrane or intracellular receptors

Question 8

What is a Strong Agonist

Answer 8

Agonist that causes max effects even though it only occupy a small fraction of receptors

Question 9

What are Weak Agonists

Answer 9

Agonists that need to be bound to many more recptors than a strong agonist does to produce same effect

Question 10

Partial Agonist

Answer 10

Drug that fails to produce max effect even when all receptors are occupied

Question 11

What is an Inverse Agonist

Answer 11

Binds to receptor and causes opposite of an agonist. Doesnt block anything from happening, it just reverses what happens

EX: H2 receptor antagonist

Question 12

What is an Antagonist?

Answer 12

Inhibit/Block actions caused by agonists

Question 13

Competetive Antagonist

Answer 13

Competes with Agonist for Receptors

• Agonist cant bind to receptor while its occupied by antagonist
• Antagonism can be overcome by high doses of agonists
• EX: Reversal agents

Question 14

Noncompetitive Antagonist

Answer 14

Binds to site other than the agonist-binding domain.

• Induces form change in receptor so that agonist no longer recognizes agonist binding domain
• Insurmountable - high doses cant defeat this antagonism
• EX: Warfarin

Question 15

Irreversible Antagonism

Answer 15

Agents compete with agonists for the agonist-binding receptor

• Antagonists bind permanently to receptor
• Rate of antagonism can be slowed by high # of antagonist

Question 16

Efficacy

Answer 16

Degree that drug is able to cause max effects

Question 17

Potency

Answer 17

Amount of drug needed to produce 50% of max effect that its capable of causing

Question 18

Potency vs. Efficacy

Answer 18

• Potency used to compare drugs in same class.
  
  • Drugs in same class usually have same max efficacy
• Efficacy used to compare drugs with different mechanisms.

Question 19

Drug-Response Curves

Answer 19

• Graphs magnitude of drug action against concentration/dose of drug needed to induce action
• Represents effects and dose of drug within individual rather than population
• Almost all meds plateau at some point

Question 20

What must be tested on a drug before they are approved for marketing?

Answer 20

Efficacy and Safety must be tested in animal and human population studies

Question 21

What kind of data is derived from testing a drug’s efficacy and safety?

Answer 21

EC₅₀: Effective Concentration 50%

LD₅₀: Lethal Dose 50%

Therapeutic Index

Margin of Safety

Question 22

What is Effective Concentration 50%

Answer 22

Effective concentration of drug in 50% of test subjects

Question 23

What is Lethal Dose 50%

Answer 23

Drug concentration that induces death in 50% of subjects

Question 24

What is Therapeutic Index

Answer 24

Measure of safety of drug

LD₅₀/ED₅₀

Question 25

What is Margin of Safety

Answer 25

Margin between therapeutic and lethal dose

Question 26

Pregnancy Category A

Answer 26

Adequate and Well-Controlled studies have failed to show risk to fetus in first trimester and later trimesters.

Question 27

Pregnancy Category B

Answer 27

Animal studies failed to show risk to fetus and no studies in pregnant women

Question 28

Pregnancy Category C

Answer 28

Animal studies show adverse effects on fetus and no studies on humans. **_BUT_** Potential benefits may warrant use on preggos despite potential risks

Question 29

Pregnancy Category D

Answer 29

Positive proof human fetal risk, **_but_** potential benefits may warrant use of drug on preggos despite potential risks.

Question 30

Pregnancy Category X

Answer 30

Animal and Human studies show fetal abmormalities and the **_risks_** **_clearly_** **_outweigh_** potential benefits EX: Warfarin, ACE Inhibitors

Question 31

Altered Absorption

Answer 31

Drugs may inhibit absorption of other drugs

Question 32

Altered Metabolism

Answer 32

Important drug interactions can occur when P450 isoenzymes inhbited or induced

Question 33

Plasma Protein Competition

Answer 33

Drugs that bind to plasma proteins may compete with other drugs for protein binding sites. EX: Drug A bumped out by Drug B may cause Toxic Drug A Levels

Question 34

Altered Excretion

Answer 34

Drugs may act on kidney to reduce excretion of specific agents

Question 35

Types of Drug Interactions

Answer 35

Addition Synergism Potentiation Antagonism

Question 36

Addition Drug Interaction

Answer 36

Combined drugs EQUALS combined reponses of each drug 1+1 = 2

Question 37

Synergism Drug Interaction

Answer 37

Combined response GREATER THAN combined response of each drug. 1+1 = 3

Question 38

Potentiation Drug Interaction

Answer 38

Drug with no effect enhances effect of second drug 0+1 = 2

Question 39

Antagonism Drug Interaction

Answer 39

Drug inhibits effect of other drug 1 + 1 = 0

Question 40

Midazolam is siginificant substrate of CYP3A4. Erythromycin is a CYP3A4 inhibitor. How to manage this drug interaction?

Answer 40

You can give same dose, but lingering effects and longer time for awakening

Question 41

Propofol is a strong CYP3A4 inhibitor. What side effects woud you expect from sedatives that are metabolized by this enzyme when given together?

Answer 41

Synergistic effect if given with versed.

Question 42

Carbamazepine is a strong CYP3A4 inducer. How might you have to alter dose of Versed if given together?

Answer 42

Give higher dose and change drugs

Question 43

Tolerance

Answer 43

Decreased response to a drug - dose must be increased for same effect.

Question 44

What is Metabolic Drug Tolerance

Answer 44

Drug metabolized more rapidly after chronic use

Question 45

What is Cellular Tolerance

Answer 45

Decreased number of receptors - downregulation

Question 46

Drug Dependence

Answer 46

* When patient needs drug to function normally * When cessation of drug = withdrawal symptoms * Physical and/or Psychological

Question 47

Abuse and Addiction

Answer 47

Use of meds not for its intended therapeutic use Use continues despite negative impacts on health, profession, social interactions

Question 48

Withdrawal

Answer 48

Occurs when drug is not given to a person who is dependent Symptoms often opposite the effects achieved by drug

Question 49

Pregnancy Registries

Answer 49

Since it's unethical for drug testing on preggos, this is where the community can report

Question 50

REMS - Risk Evaluation and Mitigation Strategy

Answer 50

Way to track drugs with high risk of very dangerous side effects.