Applied Principles of Pharmacokinetics Flashcards
What is the therapeutic index of a drug?
The therapeutic index is the ratio between the toxic dose and the effective dose of a drug.
True or False: A higher therapeutic index indicates a safer drug.
True
Fill in the blank: The therapeutic index is calculated as _____ divided by the effective dose.
toxic dose
What does a low therapeutic index suggest about a drug?
It suggests that there is a narrow margin between effective and toxic doses.
Which of the following factors can affect the therapeutic index: a) Drug metabolism, b) Patient age, c) Drug interactions?
All of the above
Short Answer: Name one factor that can increase the therapeutic index of a drug.
Improved drug formulation or targeted delivery methods.
True or False: The therapeutic index is the same for all patients regardless of individual characteristics.
False
What is the significance of the effective dose (ED50) in relation to the therapeutic index?
It is the dose at which 50% of the population experiences the desired therapeutic effect.
Fill in the blank: The _____ is the dose at which 50% of the population experiences toxicity.
lethal dose (LD50)
What role does pharmacokinetics play in determining the therapeutic index?
Pharmacokinetics affects drug absorption, distribution, metabolism, and excretion, influencing both efficacy and toxicity.
Short Answer: How can drug interactions impact the therapeutic index?
They can either enhance toxicity or reduce efficacy, altering the therapeutic index.
True or False: A drug with a wide therapeutic index may require close monitoring.
False
What is meant by the term ‘narrow therapeutic index’?
It refers to drugs that have a small difference between therapeutic and toxic doses.
Multiple Choice: Which drug is an example of one with a narrow therapeutic index? a) Warfarin, b) Acetaminophen, c) Ibuprofen
a) Warfarin
What factors can lead to variability in therapeutic index among different populations?
Genetic differences, age, sex, comorbid conditions, and concurrent medications.
True or False: The therapeutic index is static and does not change over time.
False
Fill in the blank: The _____ of a drug can influence its therapeutic index by altering its pharmacodynamics.
mechanism of action
Short Answer: Why is the therapeutic index important in drug development?
It helps determine the safety and efficacy of a drug before it is approved for use.
What is the relationship between drug clearance and therapeutic index?
Increased clearance can lower drug levels, potentially reducing efficacy and the therapeutic index.
Multiple Choice: Which factor does NOT influence the therapeutic index? a) Drug formulation, b) Environmental temperature, c) Patient adherence
b) Environmental temperature
True or False: The therapeutic index can vary based on route of administration.
True
Fill in the blank: Therapeutic index is a crucial concept in _____ medicine.
clinical
Short Answer: What is the clinical implication of a drug with a high therapeutic index?
It can be administered with less risk of adverse effects.
What is the impact of age on the therapeutic index?
Age can influence drug metabolism and sensitivity, affecting the therapeutic index.
Multiple Choice: What is the primary goal of determining the therapeutic index? a) To increase drug efficacy, b) To ensure patient safety, c) To minimize costs
b) To ensure patient safety
What is renal clearance?
Renal clearance is the volume of plasma that is completely cleared of a substance by the kidneys per unit time.
True or False: Renal clearance can be used to assess kidney function.
True.
What is the formula for renal clearance (C)?
C = (U x V) / P, where U is the urine concentration of the substance, V is the urine flow rate, and P is the plasma concentration of the substance.
Fill in the blank: The renal clearance of a drug is directly related to its ______ concentration in plasma.
plasma.
How does increased plasma concentration of a drug affect its renal clearance?
Increased plasma concentration can lead to increased renal clearance, assuming the kidneys are functioning normally.
What is the significance of the renal clearance ratio?
The renal clearance ratio helps to determine whether a substance is filtered, secreted, or reabsorbed by the kidneys.
What does a renal clearance ratio greater than 1 indicate?
It indicates that the substance is secreted by the renal tubules.
What does a renal clearance ratio less than 1 indicate?
It indicates that the substance is reabsorbed by the renal tubules.
True or False: Drugs that are highly protein-bound have a higher renal clearance.
False.
What is the impact of renal impairment on drug clearance?
Renal impairment generally leads to decreased drug clearance, resulting in higher plasma concentrations.
Define ‘steady-state concentration’ in the context of drug clearance.
Steady-state concentration is the point at which the drug’s intake and clearance are balanced, leading to stable plasma levels.
What role does tubular secretion play in renal clearance?
Tubular secretion enhances renal clearance by actively transporting substances from blood into the renal tubules.
Fill in the blank: The process of _______ can decrease renal clearance by reabsorbing substances back into the bloodstream.
reabsorption.
What factors can influence renal clearance?
Factors include kidney function, age, body weight, drug properties, and interactions with other medications.
True or False: Only unbound drugs are filtered by the kidneys.
True.
What is the relationship between renal clearance and half-life of a drug?
A higher renal clearance generally leads to a shorter half-life of the drug.
How does urine pH affect the renal clearance of weak acids and bases?
Urine pH can alter the ionization of weak acids and bases, affecting their reabsorption and clearance.
What is the effect of diuretics on renal clearance?
Diuretics increase urine production and can enhance the clearance of certain drugs.
Fill in the blank: Clearance of a drug can be affected by its _______ binding characteristics.
protein.
What is the significance of glomerular filtration rate (GFR) in renal clearance?
GFR is a key indicator of kidney function and directly influences the renal clearance of substances.
True or False: Renal clearance is the same for all drugs.
False.
What is the primary site of drug excretion in the kidneys?
The primary site of drug excretion is the renal tubules.
How can renal clearance be measured clinically?
Renal clearance can be measured using substances like creatinine or inulin, which are filtered by the kidneys.
What does it indicate if a drug has a high renal clearance?
It indicates that the drug is efficiently eliminated from the body through the kidneys.
What does ‘plasma (t1/2)’ refer to in pharmacokinetics?
Plasma half-life (t1/2) refers to the time it takes for the concentration of a drug in the plasma to reduce to half its original value.
True or False: The plasma half-life is the same for all drugs.
False
What factors can influence plasma half-life?
Factors include the drug’s clearance rate, volume of distribution, metabolic rate, and patient-specific variables such as age and health status.
Fill in the blank: The steady state plasma concentration is typically achieved after _____ half-lives.
4-5
What is meant by ‘steady state’ in pharmacology?
Steady state refers to the condition where the overall intake of a drug is equal to its elimination, resulting in a stable concentration in the plasma.
How does the plasma half-life affect the dosing frequency of a drug?
A shorter plasma half-life often requires more frequent dosing to maintain therapeutic levels, while a longer half-life may allow for less frequent dosing.
Multiple Choice: Which of the following best describes the relationship between clearance and plasma half-life? A) Directly proportional B) Inversely proportional C) No relationship
B) Inversely proportional
What is the formula to calculate plasma half-life?
t1/2 = (0.693 × Vd) / Cl, where Vd is the volume of distribution and Cl is the clearance rate.
True or False: A drug with a long half-life will reach steady state more quickly than a drug with a short half-life.
False
What is the significance of achieving steady state in drug therapy?
Achieving steady state is crucial for ensuring that drug concentrations are maintained within the therapeutic range to maximize efficacy and minimize toxicity.
Fill in the blank: The time to reach steady state is generally _____ of the drug’s half-life.
4-5 times
Short Answer: Why is it important to monitor plasma drug levels?
Monitoring plasma drug levels helps ensure that the drug concentration stays within the therapeutic range and avoids toxicity or subtherapeutic effects.
What role does volume of distribution (Vd) play in determining plasma half-life?
Volume of distribution affects how widely a drug disperses throughout the body, influencing the concentration of the drug in the plasma and thus its half-life.
Multiple Choice: Which of the following factors does NOT affect plasma half-life? A) Age B) Route of administration C) Drug color
C) Drug color
True or False: Steady state is achieved regardless of the route of administration.
True
What is the impact of renal or hepatic impairment on plasma half-life?
Renal or hepatic impairment can prolong plasma half-life due to decreased clearance of the drug from the body.
Fill in the blank: The steady state concentration can be calculated using the formula: Css = _____ / Cl.
Dose rate
What does the term ‘loading dose’ refer to?
A loading dose is an initial higher dose of a drug given to quickly achieve a desired plasma concentration.
True or False: At steady state, the rate of drug administration equals the rate of drug elimination.
True
Short Answer: How can drug interactions alter plasma half-life?
Drug interactions can induce or inhibit metabolic enzymes, affecting the clearance and thus the half-life of a drug.
What is the relationship between plasma half-life and the therapeutic window of a drug?
A drug with a short plasma half-life may have a narrow therapeutic window, requiring careful monitoring to avoid toxicity or ineffectiveness.
Fill in the blank: The concept of ‘first-order kinetics’ indicates that the rate of elimination is _____ to the drug concentration.
proportional
Multiple Choice: Which of the following is a characteristic of zero-order kinetics? A) Constant fraction eliminated B) Constant amount eliminated C) Proportional to concentration
B) Constant amount eliminated
What is zero order kinetics?
A type of reaction rate that is independent of the concentration of the reactant.
What is first order kinetics?
A type of reaction rate that is directly proportional to the concentration of one reactant.
True or False: In zero order kinetics, the rate of reaction decreases as the concentration of the reactant decreases.
False.
In first order kinetics, if the concentration of the reactant is doubled, how does the rate of reaction change?
The rate of reaction also doubles.
What is the rate equation for a zero order reaction?
Rate = k, where k is the rate constant.
What is the rate equation for a first order reaction?
Rate = k[A], where [A] is the concentration of the reactant.
Fill in the blank: In zero order kinetics, the rate is constant and does not depend on __________.
the concentration of the reactant.
What happens to the concentration of a reactant in a zero order reaction over time?
It decreases linearly with time.
What is the half-life of a first order reaction dependent on?
The half-life is constant and depends only on the rate constant k.
True or False: The half-life of a zero order reaction changes as the concentration of the reactant changes.
True.
What type of graph represents zero order kinetics?
A plot of concentration vs. time gives a straight line.
What type of graph represents first order kinetics?
A plot of the natural logarithm of concentration vs. time gives a straight line.
In what type of kinetics does saturation occur when the enzyme or catalyst is fully occupied?
Zero order kinetics.
What is the significance of the rate constant k in first order kinetics?
It indicates the speed of the reaction; higher values mean faster reactions.
Fill in the blank: In zero order kinetics, the reaction rate is __________ of the concentration of the reactants.
independent.
What happens to the reaction rate as the substrate concentration approaches saturation in a zero order reaction?
The reaction rate remains constant.
What is the effect of increasing substrate concentration in a first order reaction?
The reaction rate increases proportionally.
What is the main difference between zero order and first order kinetics?
Zero order kinetics is independent of concentration, while first order is dependent on concentration.
In which type of kinetics does the reaction rate eventually become zero as the substrate is depleted?
First order kinetics.
True or False: All enzymatic reactions exhibit first order kinetics.
False.
What is an example of a zero order reaction?
The decomposition of nitrous oxide on a surface.
What is an example of a first order reaction?
Radioactive decay.
How does temperature affect the rate of reactions in first order kinetics?
Generally, increasing temperature increases the reaction rate.
What happens to the concentration of the product in a zero order reaction?
The concentration of the product increases linearly with time.
How can you determine whether a reaction follows first or zero order kinetics experimentally?
By plotting concentration vs. time and analyzing the resulting graph shape.
What does ADME stand for in pharmacokinetics?
Absorption, Distribution, Metabolism, and Excretion
True or False: Drug interactions can only affect one component of ADME.
False
Fill in the blank: Drug interactions can alter the __________ of a drug by affecting its absorption.
bioavailability
What is the primary organ responsible for drug metabolism?
Liver
How can drug interactions affect drug distribution?
By altering protein binding and tissue permeability.
Multiple choice: Which of the following factors can influence drug absorption? A) pH levels B) Food intake C) Drug form D) All of the above
D) All of the above
What role do cytochrome P450 enzymes play in drug metabolism?
They are involved in the oxidation of drugs, affecting their clearance.
True or False: Drug interactions can lead to increased toxicity of a drug.
True
What is one way drug interactions can affect excretion?
By altering renal function or transport mechanisms.
Fill in the blank: Drug interactions can lead to __________, which can enhance or inhibit drug effects.
synergistic or antagonistic effects
What is the significance of drug half-life in the context of drug interactions?
It determines the duration and intensity of drug action, which can be altered by interactions.
Multiple choice: Which type of drug interaction occurs when two drugs compete for the same metabolic pathway? A) Pharmacodynamic B) Pharmacokinetic C) Additive D) Synergistic
B) Pharmacokinetic
True or False: Drug interactions can only occur between prescription medications.
False
What is the potential impact of food-drug interactions on absorption?
Food can enhance or inhibit the absorption of certain drugs.
Fill in the blank: A drug that increases the metabolism of another drug is called a __________.
enzyme inducer
What is the term for a drug that decreases the metabolism of another drug?
enzyme inhibitor
Multiple choice: Which of the following can be a consequence of drug-drug interactions? A) Enhanced therapeutic effect B) Increased side effects C) Reduced efficacy D) All of the above
D) All of the above
What is the relevance of volume of distribution in drug interactions?
It indicates how extensively a drug is distributed throughout the body and can be affected by interactions.
True or False: Drug interactions do not affect pediatric patients differently than adults.
False
What is a common method for assessing potential drug interactions?
Drug interaction databases or software tools.
Fill in the blank: The __________ route of drug administration can be significantly affected by drug interactions.
oral
What is the impact of drug interactions on the therapeutic index?
They can narrow the therapeutic index, increasing the risk of toxicity.
Multiple choice: Which of the following factors does NOT influence drug metabolism? A) Age B) Gender C) Time of day D) Weight
C) Time of day
True or False: All drug interactions are clinically significant.
False
What is the clinical relevance of understanding drug interactions?
To optimize therapeutic outcomes and minimize adverse effects.
