Questions and Answers
Which statement accurately describes pharmacokinetics?
In pharmacokinetics, which model describes drug distribution that occurs in two compartments?
Which parameter is NOT directly related to the elimination rate of a drug?
What characteristic primarily distinguishes zero-order kinetics from first-order kinetics?
Signup and view all the answers
Which drug has a complete bioavailability of 100%?
Signup and view all the answers
Which term is used to describe the relationship between pharmacokinetics and pharmacodynamics?
Signup and view all the answers
What is a characteristic of a one compartment model?
Signup and view all the answers
Which statement best describes zero order kinetics in relation to phenytoin?
Signup and view all the answers
How is the half-life of a drug defined?
Signup and view all the answers
In a two compartment model, what kind of decline in plasma drug concentration is typically observed?
Signup and view all the answers
What information is needed to calculate the elimination rate constant (k)?
Signup and view all the answers
What defines the concept of 'equilibrium' in a two compartment model?
Signup and view all the answers
What does maximum hepatic clearance equal?
Signup and view all the answers
What must be true if total blood clearance exceeds liver blood flow?
Signup and view all the answers
Which factor is NOT considered when calculating bioavailability for oral dosing?
Signup and view all the answers
What is the relationship between half-life and elimination rate constant?
Signup and view all the answers
Which of the following equations represents the volume of distribution?
Signup and view all the answers
What can cause a drug to have zero bioavailability despite 100% absorption?
Signup and view all the answers
Which statement about hepatic and renal function impairments is correct?
Signup and view all the answers
How is whole body clearance calculated?
Signup and view all the answers
What does a larger volume of distribution indicate about a drug?
Signup and view all the answers
What is the formula used to calculate volume of distribution?
Signup and view all the answers
What is the primary aim of Phase 1 drug metabolism?
Signup and view all the answers
Which process is primarily involved in Phase 2 drug metabolism?
Signup and view all the answers
What is meant by 'clearance' in pharmacokinetics?
Signup and view all the answers
Which factor can limit drug clearance?
Signup and view all the answers
What is the correct formula for total clearance?
Signup and view all the answers
Which of the following is NOT a characteristic of drug metabolism?
Signup and view all the answers
Which parameter is used to quantify the total drug exposure in pharmacokinetics?
Signup and view all the answers
What characterizes the absorption phase in oral dosing pharmacokinetics?
Signup and view all the answers
Which pharmacokinetic parameter is primarily used to express the rate of elimination of a drug from the body?
Signup and view all the answers
In a pharmacokinetic study using an intravenous bolus, which characteristic is unique compared to oral dosing?
Signup and view all the answers
Which factor has a significant impact on the PK/PD relationship of drugs like Cladribine?
Signup and view all the answers
Which of the following statements about volume of distribution in pharmacokinetics is true?
Signup and view all the answers
During which phase does Cmax occur in the pharmacokinetics of oral dosing?
Signup and view all the answers
What is the relationship between bioavailability and intravenous administration of a drug?
Signup and view all the answers
Study Notes
Pharmacokinetics (PK) and Pharmacodynamics (PD)
- Pharmacokinetics defines what the body does to a drug, while pharmacodynamics describes what the drug does to the body.
- The relationship between PK and PD is crucial for understanding drug therapy effectiveness.
Drug Properties
- Key pharmacokinetic parameters include dosage, clearance (Cl), volume of distribution (Vd), half-life (t1/2), and bioavailability (F).
- Example parameters for some drugs:
- Aspirin: 300 mg dose, Cl: 39 L/h, Vd: 11 L, t1/2: 0.3 hours, F: 68%
- Propranolol: 80 mg dose, Cl: 50 L/h, Vd: 270 L, t1/2: 3.9 hours, F: 36%
- Diazepam: 2 mg dose, Cl: 2 L/h, Vd: 77 L, t1/2: 55 hours, F: 100%
Rates of Reaction
- Most drugs exhibit first-order kinetics, characterized by their concentration declining exponentially over time.
- Zero-order kinetics occurs when the drug accumulates, with examples such as Phenytoin, potentially leading to overdose.
Compartment Models
- One Compartment Model: Instantaneous distribution with a single-phase decline in plasma concentration.
- Two Compartment Model: Distribution occurs between multiple compartments, resulting in a biphasic decline.
Half-life (t1/2)
- Half-life is the time required for drug concentration in plasma to decrease by 50%.
- Calculated by monitoring concentration changes; remains constant regardless of starting dose.
Volume of Distribution (Vd)
- Vd represents the extent of drug distribution in body tissues relative to the plasma.
- Formula: Vd = Dose / [A]0, where [A]0 is the initial plasma concentration adjusted for appropriate units.
Metabolism
- Drug metabolism involves irreversible chemical changes, mainly occurring in the liver.
- Divided into:
- Phase 1 Reactions: Introduce functional groups (oxidation, reduction, hydrolysis) to create inactive metabolites.
- Phase 2 Reactions: Conjugation with charged groups (glucuronidation, acylation, sulfation) enhances water solubility.
Excretion
- Clearance measures the volume of blood from which a drug is completely removed per unit time and includes both metabolism and excretion.
- The liver is the primary organ for drug clearance, impacted by enzymatic activity and blood flow (Q).
- Formula for total clearance: CLTotal = CLHepatic + CLRenal + CLMetabolic.
Bioavailability (F)
- Bioavailability indicates the fraction of the unchanged drug reaching systemic circulation after administration.
- IV administration always has 100% bioavailability; oral dosing is subject to gut and hepatic metabolism.
Key Equations
- t1/2 = 0.693 / k (relationship between half-life and elimination rate constant)
- Vd = Dose / [A]0
- CL = k × Vd
- CL = (dose × F) / AUC
PK Parameters in Studies
- In vivo studies differentiate between IV dosing, which achieves immediate plasma distribution, and oral dosing, which requires absorption.
- Parameters typically monitored include half-life, clearance, total drug exposure (AUC), and bioavailability.
Clinical Implications of PK/PD
- The relationship influences drug therapy effectiveness and safety; for instance, Cladribine affects immune response longer than plasma concentration suggests, while Midazolam's effects correspond closely with drug levels in blood.
Summary of Key Concepts
- Focus on first-order kinetics, compartment models, elimination rates, and ADME processes.
- Understand essential pharmacokinetic equations for practical applications in clinical settings.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Explore the foundational concepts of Pharmacokinetics as outlined in Dr. Richard Amison's course. This quiz covers First Principles of PK, including zero order and first order kinetics, compartment models, and the key processes of ADME (Absorption, Distribution, Metabolism, Excretion). Test your understanding of bioavailability and pharmacodynamics.
