Pharm: Principles Of Drug Action

Front 1

Define First Order kinetics

Back 1

process by which a constant percentage of substrate is metabolized per unit time (i.e half life)

Front 2

Define zero order kinetics

Back 2

a constant amount of drug is metabolized per unit time
(i.e alcohol)

Front 3

what is an agonist?

Back 3

a drug that binds to and activates a receptor

Front 4

what is a full agonist?

Back 4

a drug that binds to a recptor and has the ability to produce 100% of the maximal response

Front 5

what is a partial agonist?

Back 5

drugs that bind but produce less than 100% of the maximal possible biological response no matter how high their concentration

Front 6

what are antagonists?

Back 6

drugs that bind to receptors or other drugs and INHIBIT a biological response

Front 7

What does a competitive antagonist do?

Back 7

it binds reversibly to the same active site as the agonist, shifts the dose response curve to the right, increases the ED50

Front 8

How can a competitive antagonist be overcome?

Back 8

by increasing the concentration of the agonist; the maximal efficacy of the drug will not change

Front 9

what does a non competitive antagonist do?

Back 9

It binds irreversibly to a different site on the nzm than the agonist; it cannot be overcome by increasing the concentration of the drug; lowers Emax

Front 10

How does a non competitive antagonist effect the efficacy of a drug?

Back 10

it reduces the maximum efficacy will be reduced

Front 11

Define efficacy

Back 11

the ability to produce a biological effect

Front 12

Define potency

Back 12

a measure of the amount of drug needed to cause a biological effect; demonstrated by the ED50

Front 13

What is Kd?

Back 13

the conc. of drug yeilding 50% occupancy of the receptor; dissociation constant

Front 14

What is EC50?

Back 14

the drug concentration that produces 50% of the maximal possible response in a graded dose-response curve

Front 15

What is volume of distribution (Vd)?

Back 15

the apparent volume into which a drug is able to distribute

Front 16

Vd =

Back 16

= total drug in the body/ plasma concentration of drug

= x/Cp

Front 17

What is the significance of a large Vd?

Back 17

a large Vd signifies that most of the drug is being sequestered in some organ or compartment

Front 18

What is maintenance dose?

Back 18

a dose of drug given to achieve a therapeutic plasma concentration over an extended period of time

Front 19

Maintenance Dose =

Back 19

= Clearance x desired steady state concentration
= CL x Css

Front 20

What is loading dose?

Back 20

In some clinical situations the desired plasma concentration must be acheived quickly. In these cases a single loading dose is injected, followed by a routine maintenance dose

Front 21

Loading Dose =

Back 21

= Vd x desired Cp

Front 22

Define peak and trough concentrations

Back 22

maximum and minimum plasma concentrations, which are observed during dosing intervals

Front 23

What variables affect peak and trough concentrations?

Back 23

they will fluctuate around the steady state plasma concentration

Front 24

What is the steady state plasma concentraion (Css)?

Back 24

the point at which the rate of drug availability is equal to the rate of drug elimination

Front 25

How does frequency of dosing affect Css?

Back 25

it doesn't

Front 26

How many half lives are required to reach Css?

Back 26

approximately 4.3

Front 27

What is clearance (CL)?

Back 27

volume of plasma cleared of drug per unit time

Front 28

What is therapeutic index?

Back 28

the ratio of a drug's toxic dose to its therapeutic dose

Front 29

What do pharmacokinetics describe?

Back 29

Where the drug goes and how much needed for desired effect.

Front 30

What factors affect pharmacokinetics?

Back 30

Absorption, distribution, metabolism, and excretion.

Front 31

What affects absorption?

Back 31

Rate is affected by route of drug administration and extent is determined by metabolism and lipid solubility.

Front 32

What affects the distribution?

Back 32

Diffusion across gradient, lipid/water partitioning, charge and pH.

Front 33

Are drugs more likely to be trapped in ionized or neutral form?

Back 33

Ionized, since ions don't easily cross membranes.

Front 34

What is first pass metabolism?

Back 34

The reduction in bioavailability in orally administered drugs because of metabolism in the liver.

Front 35

What is the half-life of a drug?

Back 35

half-life = 0.693 * Vd/CL

Front 36

What are pharmacodynamics?

Back 36

This term describes how a drug works. This is determined by 1) drug-receptor interactions; 2) duration of drug action.

Front 37

What are the 2 phases in drug metabolism?

Back 37

Phase I = conversion of drug to more polar or reactive compound; Phase II = increase water solubility to increase water solubility.

Front 38

What are the cytochrome P-450 group of enzymes?

Back 38

Enzymes located in the smooth ER which help catabolize drugs.

Front 39

What is an alkanizing agent?

Back 39

bicarbonate

Front 40

What is and acidifying agent?

Back 40

ammonium chloride

Front 41

What are some factors that affect Vd?

Back 41

disease (obesity, renal disease), size (capillary permeability), lipid solubility, and charge

Front 42

What are the 3 basic reactions in Phase I of drug metabolism?

Back 42

oxidation, reduction, and hydrolysis

Front 43

P-450 is responsible for which Phase I reaction?

Back 43

oxidation

Front 44

What are 4 reactions in Phase II drug metabolism?

Back 44

glucoronidation, sulfation, acetylation and glutathione conjugation

Front 45

Which is the most important organ in drug metabolism?

Back 45

Liver is most important, followed by the kidney

Front 46

What are the 2 components of the cytochrome P-450 enzyme system?

Back 46

oxidase and reductase

Front 47

What are examples of P-450 inducers?

Back 47

barbiturates, ethanol, which enhance the metabolism of warfarin (anticoagulant) and tylenol (analgesic), respectively.

Front 48

What are examples of P-450 inhibitors?

Back 48

cimetidine and allopurinol, which decrease the metabolism of valium and tolbutamide, respectively

Front 49

What are 4 reactions in Phase II drug metabolism?

Back 49

glucoronidation, sulfation, acetylation and glutathione conjugation

Front 50

Which is the most important organ in drug metabolism?

Back 50

Liver is most important, followed by the kidney

Front 51

What are the 2 components of the cytochrome P-450 enzyme system?

Back 51

oxidase and reductase

Front 52

What are examples of P-450 inducers?

Back 52

barbiturates, ethanol, which enhance the metabolism of warfarin (anticoagulant) and tylenol (analgesic), respectively.

Front 53

What are examples of P-450 inhibitors?

Back 53

cimetidine and allopurinol, which decrease the metabolism of valium and tolbutamide, respectively

Front 54

what is an inverse agonist?

Back 54

inhibits receptor by locking it in an inactive conformation