Podcast Beta
Questions and Answers
What characterizes the distribution of a drug that has central and peripheral compartments?
Which statement accurately describes first order elimination kinetics?
In a semi-log plot for first order kinetics, what does the graphical representation look like?
What is true regarding zero order elimination kinetics?
Signup and view all the answers
What does bioavailability refer to in pharmacokinetics?
Signup and view all the answers
What is the bioavailability of drugs administered intravenously?
Signup and view all the answers
In a first order elimination process, which equation best describes the relationship between drug concentration and time?
Signup and view all the answers
What does the term 'bioavailability' in pharmacokinetics refer to?
Signup and view all the answers
In a one-compartment model, what happens to the plasma concentration of a drug when it follows first-order kinetics?
Signup and view all the answers
How is the elimination rate constant related to the half-life of a drug?
Signup and view all the answers
What is a key characteristic of a two-compartment model?
Signup and view all the answers
What is the primary principle of pharmacokinetics regarding drug effects?
Signup and view all the answers
What is the purpose of administering a drug by IV and another route for comparison?
Signup and view all the answers
How is bioavailability generally expressed mathematically?
Signup and view all the answers
What is the percent of a drug remaining in the body after three half-lives?
Signup and view all the answers
What does bioavailability indicate when a drug is administered orally?
Signup and view all the answers
What does the half-life of a drug represent?
Signup and view all the answers
Which of the following describes the volume of distribution (Vd) of a drug?
Signup and view all the answers
After four half-lives, what fraction of the drug remains in the body?
Signup and view all the answers
What formula is used to calculate the half-life of a drug in a one compartment model?
Signup and view all the answers
Which statement is true regarding drugs with high volume of distribution?
Signup and view all the answers
What is a characteristic of half-life when determined graphically?
Signup and view all the answers
What is the formula used to calculate the fraction of a drug eliminated from the body?
Signup and view all the answers
In the equation Ct = C0 e(-kxt), what does Ct represent?
Signup and view all the answers
Why is bioavailability important in pharmacology?
Signup and view all the answers
What does the area under the curve (AUC) indicate in pharmacokinetics?
Signup and view all the answers
What factor may influence the bioavailability of a drug when it is administered orally?
Signup and view all the answers
Study Notes
Pharmacokinetics Overview
- Pharmacokinetics quantifies relationships among absorption, distribution, and elimination of drugs over time.
- Blood concentration of a drug is directly related to its therapeutic effect, influencing efficacy and safety.
Key Pharmacokinetic Parameters
- Bioavailability (F): Fraction of unchanged drug reaching systemic circulation post-administration; intravenous (IV) drugs have F = 1, others < 1.
- Half-Life (t1/2): Time required for plasma drug concentration to decrease by 50%; determined using ke (elimination rate constant).
- Clearance (CL): Volume of plasma cleared of drug per unit time; inversely related to steady-state concentration.
- Volume of Distribution (Vd): Apparent volume in which drug distributes; large Vd indicates high lipophilicity or low protein binding.
- Elimination Rate Constant (ke): Rate at which drug concentration decreases over time; key in predicting drug clearance.
- Steady State Concentration (Css): Stable level of drug in the body during continuous administration; reached after 4-5 half-lives.
Compartment Models
- One-Compartment Model: Assumes rapid equilibrium between plasma and tissues; characterized by linear decline in plasma concentration in semi-log plots.
- Two-Compartment Model: Drug distributes between a central and a peripheral compartment; displays a biphasic decline in plasma concentration.
Kinetics
- First Order Kinetics: Rate of drug elimination is proportional to its concentration; results in a linear semi-log plot.
- Zero Order Kinetics: Constant amount of drug eliminated regardless of concentration; occurs when elimination pathways are saturated.
Relationship Between Parameters
- Clearance, half-life, volume of distribution, and plasma concentration are interrelated, affecting drug dosing and frequency.
- Decreases in clearance will double Css if dosing rate remains constant.
Calculating Pharmacokinetic Parameters
-
Formulas:
- Half-Life: t1/2 = 0.693 / ke
- Clearance: CL = Dose / Css
- Bioavailability: F = AUC (oral) / AUC (IV)
- Volume of Distribution calculation: Vd = Dose / (Css x ke).
Practical Applications
- Administer IV loading doses considering volume of distribution to achieve desired Css levels quickly.
- Importance of bioavailability assessment for effective drug formulation comparison and understanding absorption variability.
Additional Information
- Four half-lives rule: After 4 half-lives, a drug is considered essentially eliminated, retaining only 6% in the body.
- Knowledge of pharmacokinetics is crucial for appropriate drug therapy management, individualization of dose regimens, and optimization of therapeutic outcomes.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers the key concepts and parameters in pharmacokinetics, including bioavailability, half-life, clearance, and volume of distribution. Understanding these parameters is essential for evaluating drug efficacy and safety. Test your knowledge of how drugs are absorbed, distributed, and eliminated from the body.
