Podcast
Questions and Answers
What is the primary factor that reduces bioavailability after administration via non-IV routes?
What is the primary factor that reduces bioavailability after administration via non-IV routes?
- Increased gastric emptying
- Efficient distribution
- Incomplete absorption (correct)
- High lipid solubility
What happens to the peak concentration of a drug that is absorbed more slowly?
What happens to the peak concentration of a drug that is absorbed more slowly?
- It is lower and occurs later (correct)
- It remains unchanged
- It occurs earlier
- It becomes higher than expected
Which of the following factors does NOT influence the bioavailability of a drug?
Which of the following factors does NOT influence the bioavailability of a drug?
- First-pass hepatic metabolism
- Patient age and gender (correct)
- Solubility of the drug
- Nature of drug formulation
What is the importance of calculating the area under the curve (AUC) in pharmacokinetics?
What is the importance of calculating the area under the curve (AUC) in pharmacokinetics?
What characteristic of a drug affects its absorption across lipid-rich cell membranes?
What characteristic of a drug affects its absorption across lipid-rich cell membranes?
Which statement accurately describes bioequivalence?
Which statement accurately describes bioequivalence?
Which formulation factor is least likely to affect a drug's dissolution and absorption rate?
Which formulation factor is least likely to affect a drug's dissolution and absorption rate?
Why are drugs that are extremely hydrophobic poorly absorbed?
Why are drugs that are extremely hydrophobic poorly absorbed?
What does pharmacokinetics primarily affect regarding drugs?
What does pharmacokinetics primarily affect regarding drugs?
Which factor does NOT directly influence plasma concentration of a drug?
Which factor does NOT directly influence plasma concentration of a drug?
How is the volume of distribution (Vd) calculated?
How is the volume of distribution (Vd) calculated?
What can cause an alteration in the volume of distribution?
What can cause an alteration in the volume of distribution?
What is the primary objective in long-term drug administration?
What is the primary objective in long-term drug administration?
What does clearance (CL) help to determine in pharmacokinetics?
What does clearance (CL) help to determine in pharmacokinetics?
Which would typically NOT influence the effective drug concentration at the receptor site?
Which would typically NOT influence the effective drug concentration at the receptor site?
Which statement about the relationship between effective drug concentration and plasma concentration is incorrect?
Which statement about the relationship between effective drug concentration and plasma concentration is incorrect?
What is the relationship between clearance and plasma concentration for a drug eliminated by first-order kinetics?
What is the relationship between clearance and plasma concentration for a drug eliminated by first-order kinetics?
How is the half-life of a drug determined?
How is the half-life of a drug determined?
What happens to the half-life of a drug if clearance decreases?
What happens to the half-life of a drug if clearance decreases?
Which of the following equations describes the steady-state concentration of a drug?
Which of the following equations describes the steady-state concentration of a drug?
Which factor does NOT affect the clearance of a drug?
Which factor does NOT affect the clearance of a drug?
What is bioavailability?
What is bioavailability?
When is bioavailability considered to be 100% for a drug?
When is bioavailability considered to be 100% for a drug?
What does the equation CL = Rate of elimination / Plasma drug concentration indicate?
What does the equation CL = Rate of elimination / Plasma drug concentration indicate?
What defines two drugs as therapeutically equivalent?
What defines two drugs as therapeutically equivalent?
What is indicated by a high hepatic extraction ratio?
What is indicated by a high hepatic extraction ratio?
What is the primary purpose of a dosage regimen?
What is the primary purpose of a dosage regimen?
How is the maintenance dosage determined?
How is the maintenance dosage determined?
When is a loading dose particularly necessary?
When is a loading dose particularly necessary?
What effect does renal disease have on drug elimination?
What effect does renal disease have on drug elimination?
Which statement regarding the relationship between therapeutic and toxic concentrations is true?
Which statement regarding the relationship between therapeutic and toxic concentrations is true?
What condition may lead to reduced hepatic clearance?
What condition may lead to reduced hepatic clearance?
Study Notes
Pharmacokinetics
- Pharmacokinetics studies how the body affects drugs.
- It focuses on absorption, distribution, elimination, and how they influence drug concentration.
Effective Drug Concentration
- Concentration of drug at the receptor site determines drug effectiveness.
- This concentration is usually proportional to the drug's concentration in plasma or blood at equilibrium.
- It's a function of absorption, distribution, and elimination rates.
Volume of Distribution (Vd)
- Vd is a hypothetical volume representing how a drug spreads in the body.
- It relates the amount of drug in the body to the concentration in the plasma.
- Vd is affected by the drug's affinity for tissues.
- Conditions like liver or kidney disease can influence Vd for protein-bound drugs.
Clearance (CL)
- CL is crucial for designing drug regimens to maintain therapeutic levels.
- It represents the body's ability to eliminate a drug and is essential for steady-state concentration calculations.
- Steady-state concentration is reached when the rate of elimination equals the rate of administration.
- The relationship between dosing rate, clearance, and steady-state concentration is:
Dosage rate = CL x Css
Half-life (t1/2)
- Time it takes for drug concentration to decrease by 50%.
- Determined by Vd and CL.
- Clearance and half-life are inversely related.
- Changes in protein binding and disease states can modify half-life.
Bioavailability
- Fraction of administered dose reaching systemic circulation.
- Affected by absorption, first-pass metabolism, and distribution.
- IV administration has 100% bioavailability.
- Controlled-release formulations aim for smoother plasma concentration profiles.
- Bioavailability is calculated by comparing plasma drug levels after different routes of administration with levels achieved by IV injection.
Factors Affecting Bioavailability
- First-pass hepatic metabolism: Rapid liver metabolism reduces bioavailability.
- Solubility: Drugs must have a balance of hydrophobicity and hydrophilicity for good absorption.
- Chemical Instability: Drugs can be degraded in the gastrointestinal tract.
- Drug Formulation: Factors like particle size and excipients influence absorption.
Bioequivalence and Therapeutic Equivalence
- Bioequivalence: Similar bioavailability and time to reach peak levels.
- Therapeutic Equivalence: Similar efficacy and safety.
Extraction
- Extraction ratio: Fraction of drug removed by an organ during blood flow.
- Drugs with high hepatic extraction ratio experience substantial first-pass metabolism, leading to low oral bioavailability.
Dosage Regimens
- Plan for drug administration aiming for therapeutic concentrations without exceeding toxicity.
- Maintenance dose: Used to maintain steady-state concentrations over time.
- Loading dose: Given initially to quickly achieve therapeutic levels.
Adjusting Dosage in Disease States
- Renal or cardiac disease can decrease drug clearance, requiring dose adjustments.
- Hepatic clearance impairment can occur due to reduced liver blood flow.
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Description
This quiz covers key concepts in pharmacokinetics, including drug absorption, distribution, elimination, and effective drug concentration. It also delves into important metrics such as volume of distribution and clearance, which are vital for understanding drug efficacy and safety.
