Pharmacokinetics

Question 1

What is pharmacokinetics?

Answer 1

The study of drugs in the body – ‘what the body does to the drug’

It involves measuring and interpreting changes in drug/metabolite concentrations in plasma, urine, and other body regions over time.

Question 2

What does ADME stand for in pharmacokinetics?

Answer 2

Absorption, Distribution, Metabolism, Excretion

These are the four key processes that describe the movement of drugs within the body.

Question 3

What is pharmacodynamics?

Answer 3

Describes the effects of the drugs on the body – ‘what the drug does to the body’

It focuses on drug interactions with receptors or other molecular targets.

Question 4

Why is pharmacokinetics important in pharmacology?

Answer 4

It provides understanding of drug distribution, movement, and effects in the body

It helps in individualizing dosage and minimizing side effects.

Question 5

What is Therapeutic Drug Monitoring (TDM)?

Answer 5

Used for drugs with a narrow therapeutic range to individualize dosage and minimize side effects

It involves sequential blood samples and dose adjustments.

Question 6

What is the primary focus in pharmacokinetics development?

Answer 6

Primarily measures drug concentrations in the blood plasma

This supports the target concentration strategy linking biological effect to plasma drug concentration.

Question 7

What does the term ‘C_max’ refer to?

Answer 7

Maximum plasma concentration

It is an important descriptive pharmacokinetic parameter.

Question 8

What is ‘T_max’ in pharmacokinetics?

Answer 8

Time to achieve C_max

It indicates how quickly a drug reaches its maximum concentration in the plasma.

Question 9

What is the significance of plasma concentration (Cp)?

Answer 9

Helps account for variations in drug absorption, distribution, and elimination among individuals

It is crucial for understanding individual variability in pharmacokinetics.

Question 10

What is the purpose of allometric scaling?

Answer 10

Used to estimate human equivalent doses from animal data

It normalizes doses to body surface area rather than body weight.

Question 11

What is the definition of total drug clearance (CL-tot)?

Answer 11

Volume of plasma cleared of the drug per unit of time

It is a fundamental pharmacokinetic parameter for elimination.

Question 12

What does the term ‘linear kinetics’ mean in pharmacokinetics?

Answer 12

Drug clearance is dose-independent within the therapeutic range

Doubling the infusion rate doubles the steady-state plasma concentration.

Question 13

What is the elimination half-life (t1/2)?

Answer 13

Time for plasma concentration to decrease by half

It predicts the time course of drug concentration after starting or stopping infusion.

Question 14

What is the role of a loading dose?

Answer 14

Used to rapidly reach desired plasma concentration

Determined by volume of distribution.

Question 15

What characterizes a two-compartment model?

Answer 15

Represents drugs with distinct distribution phases (central and peripheral compartments)

It provides a more accurate representation of drug distribution.

Question 16

What are saturation kinetics?

Answer 16

A phenomenon where the rate of elimination becomes constant regardless of plasma concentration

It occurs when a carrier or enzyme becomes saturated.

Question 17

What is the significance of population pharmacokinetics?

Answer 17

Helps predict individual variation in clinical trials and clinical practice

It accounts for inter-individual variability over time.

Question 18

True or False: Monitoring plasma concentrations is always useful for drugs acting in the brain.

Answer 18

False

Plasma concentration monitoring may not reflect local concentrations in the brain due to the blood-brain barrier.

Question 19

Fill in the blank: The rate of drug elimination is described by the equation: Rate of drug elimination = Cp x _______.

Answer 19

CL-tot

Question 20

What is the primary challenge in analyzing pharmacokinetic data from diverse individuals?

Answer 20

Traditional methods involve fitting data without considering individual differences

This can lead to limitations in data quality and parameter estimates.

Question 21

What is the significance of the elimination rate constant (K_el)?

Answer 21

It represents a fraction of drug eliminated per unit of time

It is used in calculations of drug concentration over time.

Question 22

What happens to plasma concentration during a constant-rate infusion?

Answer 22

Increases towards steady-state (C_ss)

When infusion stops, concentration falls exponentially.

Question 23

What is the effect of slow absorption on peak concentration?

Answer 23

Delays and reduces peak concentration

It makes the peak less sharp.

Question 24

What is the precise relation to target concentration for drugs acting directly in the bloodstream?

Answer 24

Plausible for drugs acting directly in the bloodstream or on cell membrane targets

This indicates that monitoring target concentrations is relevant for these types of drugs.

Question 25

Is the precise relation to target concentration true for drugs acting on nuclear receptors?

Answer 25

Less likely for drugs acting on nuclear receptors or with active metabolites

This means that the relationship between plasma concentration and effect is weaker for these drugs.

Question 26

What is a unique dependence of target concentration regarding drugs that form stable covalent attachments?

Answer 26

Not true for drugs forming stable covalent attachments or producing delayed effects

Such drugs do not rely solely on target concentration for their effects.

Question 27

Give examples of drugs that may not follow the unique dependence target concentration.

Answer 27

• Aspirin
• Clopidogrel
• Some monoamine oxidase inhibitors
• PPIs

These examples illustrate drugs that have complex pharmacodynamics.

Question 28

What is a clinical implication of monitoring plasma concentrations for drugs acting in the brain?

Answer 28

Monitoring plasma concentrations may not reflect local concentrations in the brain due to BBB

BBB refers to the blood-brain barrier, which limits the correlation between plasma and brain concentrations.

Question 29

Why is plasma concentration monitoring often not clinically useful for brain-active drugs?

Answer 29

For drugs acting in the brain, plasma concentration monitoring is often not clinically useful

This is due to the inability to accurately gauge the drug’s effect in the central nervous system.

Question 30

What may cause drug effects to persist beyond their presence in plasma?

Answer 30

Drugs effects may persist beyond their presence in plasma or may be time-dependent

This alters the concentration-effect relationship.

Question 31

List examples of drugs whose effects may persist beyond their plasma concentration.

Answer 31

• Antidepressants
• Opioids
• Corticosteroids

These drugs often have prolonged effects that are not directly correlated with current plasma levels.