Pharmacokynetics V300

Question 1

Term

Answer 1

Definition

Question 2

What are the 4 phases of pharmacokinetics?

Answer 2

Absorption, Distribution, Metabolism, Excretion (ADME)

Question 3

What is bioavailability?

Answer 3

The fraction of an administered dose that reaches systemic circulation unchanged.

Question 4

What is first-pass metabolism?

Answer 4

Drug metabolism that occurs in the liver after oral administration, reducing bioavailability.

Question 5

What affects drug absorption?

Answer 5

Route of administration, gastric pH, food, formulation, and blood flow to the absorption site.

Question 6

What factors influence drug distribution?

Answer 6

Lipid solubility, plasma protein binding, blood flow, and tissue permeability.

Question 7

What is the volume of distribution (Vd)?

Answer 7

A theoretical volume that relates drug amount in the body to plasma concentration.

Question 8

What is drug metabolism and where does it occur?

Answer 8

Chemical alteration of drugs; mainly in the liver via cytochrome P450 enzymes.

Question 9

What are the two phases of metabolism?

Answer 9

Phase I: Oxidation, reduction, hydrolysis. Phase II: Conjugation (makes drug more water-soluble).

Question 10

What is drug clearance?

Answer 10

The volume of plasma from which a drug is completely removed per unit time.

Question 11

What is half-life (t½)?

Answer 11

Time taken for plasma concentration of a drug to reduce by half.

Question 12

How is elimination affected in renal impairment?

Answer 12

Decreased renal function slows elimination, requiring dose or interval adjustment.

Question 13

Which patient factors influence pharmacokinetics?

Answer 13

Age, weight, renal/hepatic function, pregnancy, genetics, drug interactions.

Question 14

What is zero-order kinetics?

Answer 14

Drug is eliminated at a constant rate regardless of concentration (e.g., alcohol).

Question 15

What is steady state?

Answer 15

When drug input equals elimination; usually achieved after 4–5 half-lives.

Question 16

Why is pharmacokinetics important for prescribing?

Answer 16

It guides safe dosing, route, timing, and choice of drug – essential for patient safety.

Question 17

Term

Answer 17

Definition

Question 18

What are the 4 phases of pharmacokinetics?

Answer 18

Absorption, Distribution, Metabolism, Excretion (ADME)

Question 19

What is bioavailability?

Answer 19

The fraction of an administered dose that reaches systemic circulation unchanged.

Question 20

What is first-pass metabolism?

Answer 20

Drug metabolism that occurs in the liver after oral administration, reducing bioavailability.

Question 21

What affects drug absorption?

Answer 21

Route of administration, gastric pH, food, formulation, and blood flow to the absorption site.

Question 22

What factors influence drug distribution?

Answer 22

Lipid solubility, plasma protein binding, blood flow, and tissue permeability.

Question 23

What is the volume of distribution (Vd)?

Answer 23

A theoretical volume that relates drug amount in the body to plasma concentration.

Question 24

What is drug metabolism and where does it occur?

Answer 24

Chemical alteration of drugs; mainly in the liver via cytochrome P450 enzymes.

Question 25

What are the two phases of metabolism?

Answer 25

Phase I: Oxidation, reduction, hydrolysis. Phase II: Conjugation (makes drug more water-soluble).

Question 26

What is drug clearance?

Answer 26

The volume of plasma from which a drug is completely removed per unit time.

Question 27

What is half-life (t½)?

Answer 27

Time taken for plasma concentration of a drug to reduce by half.

Question 28

How is elimination affected in renal impairment?

Answer 28

Decreased renal function slows elimination, requiring dose or interval adjustment.

Question 29

Which patient factors influence pharmacokinetics?

Answer 29

Age, weight, renal/hepatic function, pregnancy, genetics, drug interactions.

Question 30

What is zero-order kinetics?

Answer 30

Drug is eliminated at a constant rate regardless of concentration (e.g., alcohol).

Question 31

What is steady state?

Answer 31

When drug input equals elimination; usually achieved after 4–5 half-lives.

Question 32

Why is pharmacokinetics important for prescribing?

Answer 32

It guides safe dosing, route, timing, and choice of drug – essential for patient safety.

Question 33

What is therapeutic drug monitoring (TDM)?

Answer 33

Measuring drug levels in blood to maintain efficacy and avoid toxicity, especially for drugs with a narrow therapeutic index.

Question 34

Define the therapeutic index (TI).

Answer 34

Ratio of toxic dose to effective dose: TI = TD50 / ED50.

Question 35

How do you calculate loading dose?

Answer 35

Loading dose = (Target concentration × Vd) / Bioavailability.

Question 36

What is the formula for maintenance dose?

Answer 36

Maintenance dose = (Clearance × Target concentration) / Bioavailability.

Question 37

Why are elderly patients at higher risk of adverse drug reactions?

Answer 37

Reduced renal/hepatic function, polypharmacy, altered distribution, slower metabolism.

Question 38

How does renal failure affect drug dosing?

Answer 38

Drugs may accumulate due to impaired excretion; adjust dose or dosing interval.

Question 39

What is protein binding and why does it matter?

Answer 39

Only unbound drug is pharmacologically active; high binding affects distribution and elimination.

Question 40

Name a drug that is highly protein bound.

Answer 40

Warfarin (approx. 99% protein bound).

Question 41

How can drug-drug interactions affect metabolism?

Answer 41

Inhibitors increase drug levels; inducers reduce drug levels by altering enzyme activity.

Question 42

What is a prodrug?

Answer 42

An inactive compound metabolized into an active drug in the body (e.g., codeine → morphine).

Question 43

Why are lipid-soluble drugs more widely distributed?

Answer 43

They cross membranes more easily and accumulate in fatty tissues.

Question 44

How do pregnancy and lactation alter pharmacokinetics?

Answer 44

Increased plasma volume, altered enzyme activity, and renal clearance affect drug levels.

Question 45

What is the significance of half-life in dosing schedules?

Answer 45

It determines how frequently a drug should be administered to maintain therapeutic levels.

Question 46

How many half-lives does it take to reach steady state?

Answer 46

Approximately 4 to 5 half-lives.

Question 47

What is the clinical significance of enzyme polymorphisms?

Answer 47

Genetic differences in metabolism affect drug response and risk of side effects or failure.