Pharmacology

Question 0

What does AUC measure?

Answer 0

It measures bioavailability when the y-axis is Plasma Drug Concentration and the x-axis is time.

Question 1

What is bioavailability?

Answer 1

The extent to which a drug is absorbed and reaches systemic circulation.

Question 2

What is the variable “F”?

Answer 2

Bioavailability.

Bioavailability is the Fraction (F) of the drug is absorbed after any route of administration compared to IV administration which has a bioavailability of 100%. It can range from 1.0 (100%) to 0 (0%).

Question 3

What are some factors that affect Bioavailability?

Answer 3

1. Drug is unstable in GI tract bc of acid levels.
2. Food in GI tract.
3. Drug is charged and cannot pass thru GI mucosa.
4. First Pass Effect: Drug is biotransformed as it passes through GI mucosa and liver.

Question 4

Decreasing the rate of absorption does what to the pharmacokinetics?

Answer 4

Creates a slower rate of elimination and a longer duration of action.

Question 5

What form are drugs in when using a patch?

Answer 5

Lipid soluble non-ionized.

Question 6

What are the three routes a drug can use to cross a drug membrane?

Answer 6

Diffusion through lipids, diffusion through an aqueous layer, and using a carrier.

Question 7

What is Ka?

Answer 7

Ionization constant.

Ka = [H+][A-]/[HA]

Question 8

What is the log form of the Ka equation?

Answer 8

pH = pKa + log[A-]/[HA]

Question 9

Is pKa a constant?

Answer 9

yes

Question 10

How is the Henderson-Hasselbach equation different for acids and bases?

Answer 10

Acid: pH - pKa = log[ionized]/[nonionized]

Base: pH - pKa = log[nonionized]/[ionized]

Question 11

How does pH affect the ratio of ionization?

Answer 11

Acids: high pH means more ionization.

Base: low pH means more ionization.

Question 12

How can a drug cross the blood/brain barrier?

Answer 12

If it is lipid soluble.

Question 13

What is the partition coefficient?

Answer 13

A measure of lipid solubility. A higher partition coefficient means more lipid soluble.

Question 14

The kidney excretes drugs in what form?

Answer 14

Kidneys excrete drugs in their ionized form.

Question 15

Is the pH of urine constant, and how does that affect drug reabsorption?

Answer 15

The pH of urine is variable. A weak acid drug (aspirin) will be less ionized in acidic urine, and therefore more likely to be reabsorbed. A drug that is a weak base will more likely be ionized in acidic urine, and therefore more likely to be excreted.

Question 16

In acidic urine, what type of drug is excreted more quickly?

Answer 16

In acidic urine, basic drugs are excreted more readily.

Question 17

What is the difference between a zero order and first order reaction?

Answer 17

Zero order is not dependent on drug concentration bc it’s absorption has to do with a mechanism that is fixed, such as gastric emptying. A first order reaction is dependent on the drug concentration bc it uses diffusion or some other reaction with a concentration gradient.

Question 18

What is ED50

Answer 18

Dose required to produce a therapeutic effect in 50% of the population.

Question 19

What is TD50?

Answer 19

Dose required to produce a toxic effect in 50% of the population.

Question 20

What is the Therapeutic Index?

Answer 20

TD50/ED50

Question 21

What is Kd and Ka?

Answer 21

Kd = dissociation constant = Koff/Kon

Ka = association constant = Kon/Koff

Question 22

What’s the difference between PK and PD?

Answer 22

Pharmacokinetics: What the body does to the drug.

Pharmacodynamics: What the drug does to the body.

Question 23

What is the equation for dose?

Answer 23

Dose = Concentration x Volume

Question 24

Does a lipophilic drug have a larger or smaller apparent volume of distribution (V or Vd)?

Answer 24

Larger. It if is lipophilic it can be absorbed by fats; if it is only water soluble then it gets excreted in urine.

Question 25

Other than lipid solubility, what else affects Apparent Volume of Distribution?

Answer 25

Plasma protein binding because it keeps the drug in the blood compartment.

Question 26

What is the Elimination Rate Constant?

Answer 26

K = ln(2)/(half life)

Question 27

What is Clearance?

Answer 27

Clearance = Dose/AUC

Question 28

Time to steady state (ss) is dependent on what?

Answer 28

Half-Life.

Question 29

What is the equation for finding the Maintenance Dose?

Answer 29

Maintenance Dose = V * (Cmax - Cmin)

Question 30

How do you calculate the Maintenance Dose Interval?

Answer 30

Maintenance Dose Interval = 2.303/k * log(Cmax/Cmin)

Question 31

What is the equation for Loading Dose?

Answer 31

Loading Dose = V * Cmax

Question 32

What is the equation for Infusion Rate?

Answer 32

Infusion Rate (ko) = CL x C, or ko = V x k x C

k = elimination constant

Question 33

What are the equations for an IV bolus and maintenance infusion?

Answer 33

Loading Dose (Bolus) = Css x V

Maintenance Infusion = CL x Css

Question 34

What is genetic heterogeneity?

Answer 34

The different genotypes with the same phenotype.

Question 35

What is allelic heterogeneity?

Answer 35

Different abnormalities at the same locus creating the same phenotype.

Question 36

What is a founder’s effect?

Answer 36

Genetic diseases that are especially prevalent in a small populations, -ie Ty Sach’s Disease in the Ashkenazi Jews.

Question 37

What is pleiotropy?

Answer 37

Mutant genes affect multiple organ systems.

Question 38

What is penetrance?

Answer 38

of people with genotype and phenotype / # of people with genotype.