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Questions and Answers
What is the most important plasma protein for drug binding?
What is the most important plasma protein for drug binding?
What primary factor does drug binding degree depend on?
What primary factor does drug binding degree depend on?
Which patients would likely experience the greatest alterations in drug binding?
Which patients would likely experience the greatest alterations in drug binding?
Drugs absorbed by the gastrointestinal tract must first pass through which organ?
Drugs absorbed by the gastrointestinal tract must first pass through which organ?
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What is the term for the effect that occurs when drugs first pass through the liver?
What is the term for the effect that occurs when drugs first pass through the liver?
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How does drug concentration influence diffusion across a membrane?
How does drug concentration influence diffusion across a membrane?
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Which of the following factors does NOT affect drug diffusion across a membrane?
Which of the following factors does NOT affect drug diffusion across a membrane?
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What is the primary mechanism by which drugs cross cell membranes?
What is the primary mechanism by which drugs cross cell membranes?
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What is the significance of chiral drugs in pharmacology?
What is the significance of chiral drugs in pharmacology?
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In pharmacokinetics, what does the term 'volume of distribution' refer to?
In pharmacokinetics, what does the term 'volume of distribution' refer to?
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What role do receptor modulators play in pharmacology?
What role do receptor modulators play in pharmacology?
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Which parenteral route allows for sustained dose release and avoids the GI tract?
Which parenteral route allows for sustained dose release and avoids the GI tract?
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What determines the half-life of a drug in the body?
What determines the half-life of a drug in the body?
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Which mechanism is responsible for the movement of drugs from an area of low concentration to high concentration?
Which mechanism is responsible for the movement of drugs from an area of low concentration to high concentration?
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Which statement correctly describes renal clearance?
Which statement correctly describes renal clearance?
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What type of drug absorption is characterized by complete absorption?
What type of drug absorption is characterized by complete absorption?
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Which route is commonly used for drug delivery in general anesthesia?
Which route is commonly used for drug delivery in general anesthesia?
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Which form of a drug is typically pharmacologically active?
Which form of a drug is typically pharmacologically active?
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In which scenario would you expect vasoconstrictors to be administrated?
In which scenario would you expect vasoconstrictors to be administrated?
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What is the primary transport mechanism that does not require energy?
What is the primary transport mechanism that does not require energy?
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Which parenteral route is often used for patients who do not have IV access?
Which parenteral route is often used for patients who do not have IV access?
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What is the primary focus of pharmacokinetics?
What is the primary focus of pharmacokinetics?
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Which of the following components is NOT part of pharmacokinetics?
Which of the following components is NOT part of pharmacokinetics?
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What is first-pass elimination?
What is first-pass elimination?
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Why is the study of drug distribution important in pharmacokinetics?
Why is the study of drug distribution important in pharmacokinetics?
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Which term describes the specific area where a drug interacts with its receptor for clinical effect?
Which term describes the specific area where a drug interacts with its receptor for clinical effect?
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What can impact the pharmacokinetic process of a drug?
What can impact the pharmacokinetic process of a drug?
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What advantage does an intravenous route provide in pharmacokinetics?
What advantage does an intravenous route provide in pharmacokinetics?
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What is the significance of studying pharmacodynamics in contrast to pharmacokinetics?
What is the significance of studying pharmacodynamics in contrast to pharmacokinetics?
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Which process primarily removes drugs from the plasma?
Which process primarily removes drugs from the plasma?
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What is directly related to the clearance of a drug?
What is directly related to the clearance of a drug?
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A high hepatic extraction ratio indicates that a drug is which of the following?
A high hepatic extraction ratio indicates that a drug is which of the following?
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Which route of elimination is primarily considered when referring to organ-independent elimination?
Which route of elimination is primarily considered when referring to organ-independent elimination?
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What factor does NOT influence renal elimination of a drug?
What factor does NOT influence renal elimination of a drug?
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What happens to drugs in acidic urine?
What happens to drugs in acidic urine?
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Which factor typically increases half-life of a drug?
Which factor typically increases half-life of a drug?
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What is true regarding drug clearance and half-life?
What is true regarding drug clearance and half-life?
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Which drug type is likely to undergo significant first-pass metabolism?
Which drug type is likely to undergo significant first-pass metabolism?
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What effect does renal insufficiency have on drug metabolism?
What effect does renal insufficiency have on drug metabolism?
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The term 'clearance' refers specifically to which of the following?
The term 'clearance' refers specifically to which of the following?
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What describes drugs with a low hepatic extraction ratio?
What describes drugs with a low hepatic extraction ratio?
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What is the primary determinant for renal excretion of drugs?
What is the primary determinant for renal excretion of drugs?
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In which condition would the elimination of a drug likely be highest?
In which condition would the elimination of a drug likely be highest?
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What is the theoretical definition of the Volume of Distribution (Vd)?
What is the theoretical definition of the Volume of Distribution (Vd)?
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When is a larger Volume of Distribution (Vd) likely to be required?
When is a larger Volume of Distribution (Vd) likely to be required?
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Which patient characteristic can significantly influence Volume of Distribution (Vd)?
Which patient characteristic can significantly influence Volume of Distribution (Vd)?
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If a drug has a Volume of Distribution (Vd) that exceeds total body water, what can be inferred?
If a drug has a Volume of Distribution (Vd) that exceeds total body water, what can be inferred?
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What effect does an increasing Volume of Distribution (Vd) have on plasma drug concentration?
What effect does an increasing Volume of Distribution (Vd) have on plasma drug concentration?
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Which of the following drugs is associated with a Volume of Distribution (Vd) less than total body water?
Which of the following drugs is associated with a Volume of Distribution (Vd) less than total body water?
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In a two-compartment model, the central compartment includes which of the following organs?
In a two-compartment model, the central compartment includes which of the following organs?
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What is the effect of bolus dosing in relation to Volume of Distribution (Vd)?
What is the effect of bolus dosing in relation to Volume of Distribution (Vd)?
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How does drug elimination impact the Volume of Distribution (Vd)?
How does drug elimination impact the Volume of Distribution (Vd)?
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How does protein binding affect the Volume of Distribution (Vd) of a drug?
How does protein binding affect the Volume of Distribution (Vd) of a drug?
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What constitutes a target controlled infusion in drug administration?
What constitutes a target controlled infusion in drug administration?
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Which of these factors affects the distribution of drugs within the compartments?
Which of these factors affects the distribution of drugs within the compartments?
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In which scenario would volume of distribution (Vd) approximately double?
In which scenario would volume of distribution (Vd) approximately double?
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What is one of the main assumptions made when considering Volume of Distribution (Vd)?
What is one of the main assumptions made when considering Volume of Distribution (Vd)?
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Study Notes
Introduction to Pharmacology: PharmacoKinetics
- Pharmacology aims to prevent, cure, and control disease.
- Anesthesia involves responses to physiological changes, using sedation, general anesthesia, and amnesia. Analgesia, muscle relaxation, and prevention of complications are also important.
- Safety is crucial in pharmacology.
- PharmacoKinetics studies how the body affects a drug. Dose and plasma concentrations are related here. Factors impacting this include absorption, distribution, metabolism, and elimination.
- PharmacoDynamics studies how a drug affects the body. The relationship between effect site concentration and clinical effects is central here.
- PharmacoBioPhasics focuses on specific areas/effects where drug/receptor engagement creates a clinical effect.
PharmacoKinetics
- Absorption is the transfer of a drug from the administration site into the bloodstream.
- Absorption rate and efficacy depend on the route of administration. Oral intake, injection, inhalation, and topical/transdermal routes are discussed.
- Distribution is the movement of a drug from the plasma into tissues/cells.
- Influencing factors include blood flow to tissues, capillary permeability, and drug structure.
- Molecular size influences how easily drugs cross cell barriers. Smaller molecules typically cross easier.
- Protein binding affects drug distribution.
- Binding to albumin is important.
Factors Affecting Drug Absorption
- Routes of administration: Intramuscular, inhaled, subcutaneous, intravenous, oral, buccal, rectal.
- Blood flow to absorption sites: Heat increases absorption; vasoconstriction decreases it.
- Drug solubility: High lipid solubility (lipophilic) drugs absorb faster.
- Surface area of the absorption site plays a role in absorption rate.
Distribution
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Distribution is the process by which a drug leaves the administration site and enters the plasma and cells.
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Influencing Factors:
- Blood flow to tissues
- Capillary permeability
- Drug structure
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Molecular size influences distribution.
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Active transport requires energy, whereas passive transport follows concentration gradients. This affects drug transfer speed.
Protein Binding
- Drugs bind to plasma proteins, often albumin.
- Bound drug is "trapped" in plasma; free drug enters tissues.
- Protein binding affects a drug's distribution and elimination.
Compartments
- Body water compartments are key for understanding drug distribution.
- The following are included:
- total body water
- intracellular fluid
- extracellular fluid
- interstitial fluid
- plasma
- A 70 kg person has approximately 42L total body water; intracellular, extracellular compartments are explained.
Volume of Distribution (Vd)
- Theoretical volume necessary to contain the same concentration of unbound drug in plasma & interstitial fluid
- Larger Vd suggests more drug in tissues compared to plasma.
- Vd is calculated using: Loading dose = Vd x Desired Plasma Concentration.
Metabolism
- Metabolism is the process altering drug structure to make it easier to eliminate, by turning it into a polar/water-soluble form.
- Sites include liver, plasma, kidneys, lungs, and gastrointestinal tract.
- Enzymes are important in this process.
- Metabolism can create active metabolites or inactive products
- Includes oxidation, reduction, and hydrolysis processes.
- The first phase often converts the compound to a more polar form increasing hydrophilicity (water-soluble).
- The second (conjugation) phase adds a polar group to the modified molecule
Elimination
- Elimination is the irreversible removal of drugs from the body.
- Routes include:
- Kidneys (urine)
- Liver (bile into feces)
- Lungs (exhalation)
- Other (sweat, saliva)
Clearance
- Removal of drug from plasma over time.
- Directly related to organ blood flow, fraction of removed drug and dose.
- Inversely related to the half-life, drug concentration in central compartment.
Hepatic Extraction Ratio
- Comparison of arterial versus venous concentration of a drug reflecting the efficiency of liver extraction.
- "High extraction ratio" suggests a drug extraction and clearance that is flow dependent.
- Propofol, ketamine, lidocaine, bupivacaine, fentanyl, morphine, metoprolol, nitroglycerin (are all examples of high extraction ratio drugs)
- "Low extraction ratio" suggests a drug extraction and clearance that is capacity-dependent
- Rocuronium, lorazepam, methadone, thiopental, warfarin, phenytoin (are all examples of low extraction ratio drugs)
Renal Elimination & Excretion
- Renal processes for drug removal
- Glomerular filtration - process
- Proximal tubular secretion - process of actively transporting drugs into tubular filtrate
- Distal tubular reabsorption - process whereby unionized drug potentially passively returns to the bloodstream
Half-Life (t1/2)
- Time for the plasma concentration of a drug to decrease by approximately 50%.
- Factors influencing half-life:
- Volume of distribution
- Clearance
Kinetics of Metabolism
- Zero-order kinetics: Constant amount of drug metabolized per unit time.
- Alcohol, aspirin
- First-order kinetics: Constant fraction metabolized per unit time.
- Most anesthetics
Steady State
- Steady state reached when the rate of drug administration equals the rate of drug elimination.
- Takes approximately 4-5 half-lives to reach.
Injection and Infusion Kinetics
- Injection and infusion kinetics describe drug movement and/or elimination from body.
- Important variables include:
- Distribution
- Redistribution
- Metabolism
- Excretion
- Important variables include:
- One or multi-compartment models demonstrate how drug distributes in the body.
Multi-Compartment Models
- Two- and three-compartment models demonstrate more complex drug distribution in the body.
- Drug movement between different compartments is dependent upon factors such as:
- Volume of Distribution
- Plasma and tissue concentration
- Rate constants (k)
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Description
Test your knowledge on the important aspects of drug binding in pharmacology. This quiz covers key concepts such as plasma proteins, drug absorption, and the effects of the liver on drugs. Challenge yourself with questions about how drugs interact with membranes and factors affecting drug diffusion.