Learning Assessment 1

Question 1

TD 50

Answer 1

The median toxic dose of a drug is the dose at which toxicity occurs in 50% of
cases.

Question 2

Ed 50

Answer 2

The effective dose for 50% of the population (Median effective dose). The ED50 is
commonly used as a measure of the reasonable expectancy of a drug effect, but
does not necessarily represent the dose that a clinician might use.

Helps in understanding the median dose where 50% of the population has a
therapeutic response.

Question 3

Ec50

Answer 3

The effective concentration of a drug which induces a response halfway between the
baseline and maximum after a specified exposure time. (Median effective
concentration)
It is commonly used as a measure of a drug’s potency.

Ed 50 can be used to compare the potency of two drugs, the lower the EC50 the more potent

Helps in understanding the median effective concentration of a drug. Helps in comparing potency of similar drugs in a class.

Question 4

Ic50

Answer 4

The the concentration of an inhibitor where the response (or binding) is reduced by
half.

Question 5

Therapeutic index

Answer 5

 The therapeutic index ( also referred to as therapeutic ratio) is a comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes toxicity.

relationship between the TD50 and ED50

Question 6

graded response

Answer 6

Biologic effects that can be measured continually in response to a medication:
 Blood pressure 
 Heart Rate 
 Diuresis 
 Bronchodilation 
 Pain

Question 7

quantal response

Answer 7

Effects that may or may not occur  (Present or absent)
 Seizures
 Pregnancy
 Rash
 Sleep
 Death

Question 8

pharmacodynamics

Answer 8

(What the drug does to the body): (Mechanisms of Action)

• Interactions with Receptors
• Non-receptor mechanisms

Question 9

pharmacokinetics

Answer 9

(What the body does to the drug)
Absorption
Bioavailability 
Distribution 
Metabolism 
Elimination

Question 10

receptor mechanisms

Answer 10

Ion Channel Receptors  
G Protein Receptors 
Enzyme-Linked Receptors 
Intracellular Receptors
Ion exchangers

target receptors include: 
enzymes
ion channels
cell surface receptors
transporters DNA

Question 11

non-receptor mechanisms

Answer 11

chemical action
neutralization (antacids), chelation (penicillamine), ion exchangers (cholestyramine)

physical action: osmosis, absorption, demulcents, counterfeit incorporation (sulfa drugs/ neoplastics)

Question 12

ligand

Answer 12

A molecule (drug/hormone/neurotransmitter) that binds to a receptor forming a ligand-receptor complex. May activate or inhibit. agonist or antagonist)

Question 13

substrate

Answer 13

molecule upon which an enzyme acts

Question 14

agonist

Answer 14

binds to a receptor and produces an effect

Question 15

antagonist

Answer 15

binds to a receptor and odes not produce an effect

blocks receptor and prevents endogenous compounds from binding to the receptor

Question 16

competative agonist/ antagonist

Answer 16

morphine/ naloxone

Question 17

partial agonist

Answer 17

binds to a receptor that stimulates only some of the receptors

Question 18

ion channel receptors

Answer 18

Transmit signals across cell
membrane by increasing the
flow of ions and altering the
electrical potential or
separation of charged ions
across the cell membrane
 Drugs that target ion channel
receptors
 Amlodipine  Zolpidem  Alprazolam  Sulfonylureas  Repaglinide

Question 19

g protein coupled receptor

Answer 19

Alpha and Beta adrenergic
drugs
 Albuterol  Losartan  Morphine  Clopidogrel  haloperidol

Question 20

enzyme-linked receptors

Answer 20

Examples of drugs that
target enzyme-linked
receptors:
 Antibiotics 
 Atorvastatin 
 Insulin 
 Heparin

Question 21

intracellular receptors

Answer 21

Examples of drugs that target
intracellular receptors:
 Corticosteroids
 Glucocorticoids
 Mineralocorticoids 
 Thyroid Hormones

Question 22

absorption

Answer 22

pharmacokinetics

how the drug enters the body affects: bioavailability, onset of action, durations of action, patient adherence

Question 23

first-pass effect/ metabolism

Answer 23

drugs are metabolized at a specific location in the body that results in a reduced concentration of the active drug upon reaching its site of action or the systemic circulation

A drug is absorbed from the GI tract
and passes via the portal vein into the
liver where some drugs are
metabolized (bypassing general
circulation) Sometimes the result
of first pass metabolism means that
only a proportion of the drug reaches
the circulation. First pass
metabolism can occur in the gut and
the liver.

 Drugs with high first pass effect
include verapamil (remember in the
previous slide we said verapamil
given orally had low bioavailabilty F
factor?  This is in part due to the high
degree of first pass effect.

Question 24

bioavailability

Answer 24

fraction of the administered drug that enters the bloodstream

f= drug administered/ drug that enters the bloodstream

parenteral has the greatest bioavailability 100%

Question 25

distribution

Answer 25

the drug traveling to its site of action to produce a pharmacodynamic effect
passive distribution and active transport
protein binding (think physiologic states that affect protein binding such as hypoalbuminemia)
transport systems
volume of distributions

volume of distribution (Bd)= amt of drug in the body/ concentration of drug in the blood

larger distribution usually causes increased drug concentrations in the tissue and decreased concentrations in the plasma

Question 26

metabolism

Answer 26

Metabolism is chemical alteration or biotransformation by enzymes into
new molecules (metabolites)
 Sometimes metabolism is required to achieve the “active metabolite.”
 The degree of metabolism can increase or decrease a drug
 onset
 duration of action and
 toxicity of drug

metabolism mostly occurs in the liver

metabolism, in general, makes these molecules more water-soluble so they can be excreted by the kidneys (mostly n the smooth endoplasmic reticulum of liver cells)

Question 27

phase I metabolism

Answer 27

involve oxidation, reduction and hydrolysis reactions, mixed-function oxidase system
cytochrome P 450
CYP P450 enzymes

results in metabolites with greater or lesser pharmacologic activity
some phase I metabolites are rapidly eliminate4d, others go to phase II metabolism

CYP 450 enzymes may inhibit (decrease) metabolism which leads to
higher plasma drug levels and decreased clearance
Or
 CYP450 enzymes may induce (increase) metabolism which leads to
lower plasma drug levels and increased clearance

Question 28

phase II metabolism

Answer 28

conjugation reactions
metabolites are linked into highly polar molecules making them more water-soluble and thus easily eliminated from the body

increased solubility leads to increased excretion of the drug