Clinical Pharmacokinetics Quiz
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Questions and Answers

What aspect of a drug is primarily responsible for exerting its pharmacological effect?

  • The protein binding capacity of the drug
  • The free level of the drug (correct)
  • The total amount of drug administered
  • The drug's volume of distribution

    • What does a low volume of distribution (Vd) indicate about a drug?

  • The drug is excreted quickly from the body
  • The drug is widely distributed in body tissues
  • The drug has a low therapeutic index
  • A high percentage of the drug is bound to plasma proteins (correct)

    • Which of the following scenarios would make considering protein binding of a drug critical?

  • The drug is primarily excreted in the urine
  • The drug has a very narrow therapeutic index (correct)
  • The drug has a high volume of distribution
  • The drug does not bind to plasma proteins

    • How is the volume of distribution (Vd) expressed?

    <p>Liters (L) or liters per kilogram (L/kg) (B)</p> Signup and view all the answers

    Which drug would likely experience significant interactions due to its high level of protein binding?

    <p>Warfarin (D)</p> Signup and view all the answers

    What does pharmacokinetics refer to?

    <p>Study of administration, distribution, metabolism, and excretion (D)</p> Signup and view all the answers

    Which of the following is a key component of clinical pharmacokinetics?

    <p>Application of pharmacokinetic principles for individual patients (D)</p> Signup and view all the answers

    Which factor is NOT typically involved in drug absorption?

    <p>Time of day (C)</p> Signup and view all the answers

    What is the significance of loading doses in pharmacokinetics?

    <p>They help achieve steady state concentrations rapidly (C)</p> Signup and view all the answers

    What distinguishes linear pharmacokinetics from nonlinear pharmacokinetics?

    <p>The relationship between dose and concentration (A)</p> Signup and view all the answers

    What is the characteristic of metabolizing enzymes and transporters in terms of elimination kinetics?

    <p>They are unsaturated, following first order kinetics. (A)</p> Signup and view all the answers

    What determines how much of a drug is excreted in the urine?

    <p>Urine pH and the ionization state of the drug. (D)</p> Signup and view all the answers

    To reduce the tubular absorption of a weak acid like aspirin in case of overdose, how should urine pH be altered?

    <p>Make urine alkaline to increase ionization. (D)</p> Signup and view all the answers

    How long does it typically take to reach steady state for a drug following first order elimination?

    <p>4-5 half lives. (D)</p> Signup and view all the answers

    What is the purpose of administering a loading dose (LD)?

    <p>To quickly achieve effective plasma concentrations. (D)</p> Signup and view all the answers

    What is the primary organ responsible for drug metabolism in the body?

    <p>Liver (B)</p> Signup and view all the answers

    Which type of kinetics describes the metabolism of most medications under normal concentrations?

    <p>First order kinetics (C)</p> Signup and view all the answers

    What happens to the metabolism rate when drug concentration is greater than the Michaelis constant (Km)?

    <p>Metabolism rate is constant (D)</p> Signup and view all the answers

    What is a prodrug?

    <p>An inactive compound until metabolic activation (D)</p> Signup and view all the answers

    Which phase of drug biotransformation involves oxidation, reduction, and hydrolysis?

    <p>Phase I (B)</p> Signup and view all the answers

    Which of the following drugs is known to follow zero order kinetics at therapeutic concentrations?

    <p>Aspirin (C)</p> Signup and view all the answers

    What effect can liver dysfunction have on drug clearance?

    <p>Halves the drug clearance (D)</p> Signup and view all the answers

    Which of the following statements about metabolites is true?

    <p>Some metabolites have little or no pharmacological activity (D)</p> Signup and view all the answers

    What is a major disadvantage of the enteral route of drug administration?

    <p>Exposed to harsh gastrointestinal conditions (B)</p> Signup and view all the answers

    What does bioavailability indicate in pharmacology?

    <p>Fraction of drug reaching systemic circulation (B)</p> Signup and view all the answers

    Which of the following is NOT a factor that affects drug absorption?

    <p>Organ blood flow (D)</p> Signup and view all the answers

    What is a significant advantage of parenteral drug administration?

    <p>No gastrointestinal absorption required (B)</p> Signup and view all the answers

    What is the first pass effect in relation to oral medications?

    <p>Metabolism of drugs before reaching systemic circulation (A)</p> Signup and view all the answers

    Which of the following correctly describes a drawback of parenteral drug administration?

    <p>Higher risk of infection (A)</p> Signup and view all the answers

    Which substance is most likely to have a bioavailability of 100%?

    <p>Intravenous drug (A)</p> Signup and view all the answers

    What primarily determines the distribution of a drug within the body?

    <p>Organ blood flow (B)</p> Signup and view all the answers

    Which of the following statements about microsomal metabolism is correct?

    <p>Hydroxylation and dealkylation are common oxidations performed by these enzymes. (D)</p> Signup and view all the answers

    What effect does carbamazepine have on drug metabolism?

    <p>It enhances the metabolism of warfarin as an enzyme inducer. (C)</p> Signup and view all the answers

    Which of the following is a type of nonmicrosomal metabolism?

    <p>Hydrolysis (A)</p> Signup and view all the answers

    What processes are included in the elimination of drugs from the body?

    <p>Biotransformation to inactive compounds and renal excretion (D)</p> Signup and view all the answers

    What does the term half-life (T1/2) refer to in pharmacokinetics?

    <p>The interval necessary to decrease the plasma concentration of a drug to 50%. (C)</p> Signup and view all the answers

    Which statement correctly describes clearance (CL) in pharmacology?

    <p>Clearance is a constant value under clinical settings. (C)</p> Signup and view all the answers

    In phase II metabolism, which of the following is an example of glucuronidation?

    <p>Morphine (A)</p> Signup and view all the answers

    Which of the following statements is true about enzyme inhibitors?

    <p>Cimetidine is an example that affects the metabolism of diazepam. (A)</p> Signup and view all the answers

    Flashcards

    Pharmacokinetics

    The study of how the body affects a drug, including absorption, distribution, metabolism, and excretion (ADME).

    Clinical Pharmacokinetics

    Applying the principles of pharmacokinetics to individual patients for safe and effective drug treatment.

    Route of Administration

    The way a drug is given, such as orally, intravenously, or topically.

    Local Route of Administration

    The drug is delivered directly to the site of action, such as a cream applied to the skin.

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    Systemic Route of Administration

    The drug enters the bloodstream and is distributed throughout the body.

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    Enteral Route

    The route of drug administration where the drug is swallowed and absorbed through the digestive system.

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    Parenteral Route

    The route of drug administration where the drug is injected directly into the bloodstream, bypassing the digestive system.

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    Drug Absorption

    The process of a drug moving from the site of administration into the bloodstream.

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    Bioavailability

    The percentage of the administered drug that reaches the systemic circulation.

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    First Pass Metabolism

    The breakdown of a drug by enzymes, primarily in the liver, before it reaches the systemic circulation.

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    Drug Distribution

    The movement of a drug from the bloodstream to various organs and tissues.

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    Organ Blood Flow

    The extent to which blood flow to a specific organ or tissue influences drug distribution.

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    Plasma Protein Binding

    The binding of drugs to plasma proteins, which can limit their availability to reach target tissues.

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    Protein Binding

    The amount of drug bound to plasma proteins is important for determining the drug's effectiveness. Higher protein binding means less available drug for the body to use.

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    Small Volume of Distribution

    A small volume of distribution means that most of the drug stays in the bloodstream instead of distributing to other tissues. It's like the drug is comfortable just hanging out in the blood, not wanting to go explore.

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    Volume of Distribution (Vd)

    The volume of distribution is a measure of how much fluid is needed to contain all the drug in the body. It helps us understand where the drug is located (bloodstream vs. tissues).

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    Low Therapeutic Index

    A low therapeutic index means that there's a small difference between the effective dose and the toxic dose of the drug, making it harder to find the right dose.

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    Drug Elimination

    The process by which the body gets rid of drugs. It includes breaking the drug down (metabolism) and removing it from the body (excretion).

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    Drug Metabolism

    The process of converting drugs into more water-soluble compounds, making them easier to excrete from the body.

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    First-Order Kinetics

    The rate of metabolism is proportional to the drug concentration.

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    Zero-Order Kinetics

    The rate of metabolism is constant, regardless of the drug concentration.

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    Phase I Metabolism

    Chemical reactions that modify drug molecules, including oxidation, reduction, or hydrolysis. This is the first step in breaking down drugs.

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    Phase II Metabolism

    Reactions that attach water-soluble molecules to the drug, making it readily excretable.

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    Steady state

    The point at which the rate of drug input equals the rate of drug elimination.

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    Loading dose

    The amount of drug needed to rapidly achieve a therapeutic concentration in the body.

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    Renal drug excretion

    The process of removing drugs from the body, including filtration, secretion, and reabsorption.

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    Microsomal Enzymes (Cytochrome P450 Enzymes)

    A family of enzymes found in the endoplasmic reticulum (ER) of cells like the liver, lung, and gut, responsible for oxidizing drugs and other foreign compounds.

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    Enzyme Inducers

    Substances that increase the activity of cytochrome P450 enzymes, leading to faster drug metabolism and potentially lower drug levels.

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    Enzyme Inhibitors

    Substances that decrease the activity of cytochrome P450 enzymes, leading to slower drug metabolism and potentially higher drug levels.

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    Hydrolysis (Nonmicrosomal Metabolism)

    A process of drug metabolism that involves the addition of a water molecule, breaking down the drug molecule.

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    Monoamine Oxidases

    Enzymes that break down amine neurotransmitters and other compounds.

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    Elimination

    The process of removing drugs and their metabolites from the body.

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    Half-Life (T1/2)

    The time it takes for the plasma concentration of a drug to decrease by 50%.

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    Clearance (CL)

    The volume of plasma that is cleared of a drug per unit time. It represents the efficiency of drug removal from the body.

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    Study Notes

    Introduction to Pharmacology

    • The lecture is about pharmacokinetics.
    • Pharmacokinetics is the study of drug administration, distribution, metabolism and excretion (ADME).
    • Clinical pharmacokinetics applies these concepts to provide safe and effective patient care.

    Key Learning Outcomes

    • Understand pharmacokinetics in clinical settings.
    • Know the main routes of drug administration.
    • Understand influencing factors of drug absorption and distribution, and be able to apply relevant equations.
    • Know factors influencing drug metabolism and excretion and be familiar with drug half-life and clearance equations.
    • Understand the difference between linear and non-linear kinetics.
    • Understand how steady-state therapeutic plasma concentrations (Cpss) are reached and how loading doses are used to achieve them more rapidly.

    Routes of Drug Administration

    • Enteral: Oral, sublingual, rectal
      • Advantages: convenient, painless, non-invasive
      • Disadvantages: first pass metabolism, slow onset, variable absorption
    • Parenteral: Injections (IV, IM, SC, etc.), inhalational, transdermal, intradermal, intranasal, topical, ocular, otic.
      • Advantages: rapid onset, high bioavailability
      • Disadvantages: risk of infection, requires healthcare professional

    Site of Administration

    • There are two major classification of drug administration routes, systematic (which is absorbed into the systemic circulation)and local (which acts locally at the site of administration).
    • Routes listed in the slideshow: oral, sublingual, rectal, inhalational, intravenous, intramuscular, subcutaneous, intra-arterial, intra-articular, intrathecal, intradermal, skin topical, intranasal, ocular drops, mucosal-throat, vagina, mouth, ear, transdermal

    Pharmaceutical Process

    • Drug formulation (solid or liquid)
    • Site of administration (Local or Systemic)

    Absorption

    • Absorption rate
    • Bioavailability (f)
      • Fraction of drug reaching systemic circulation
      • Affected by route of administration, drug form, patient-specific factors like GI and hepatic transporters and enzymes
      • IV drugs have 100% bioavailability.
    • First-pass effect
      • Metabolism of drugs passing through the liver before reaching systemic circulation.
      • Affects bioavailability of oral drugs.
    • Determinants of drug absorption:
      • Solubility
      • Concentration gradients:
      • Surface area and vascularity

    Distribution

    • Distribution of drug molecules from systemic circulation into target organs and tissues.
    • Factors affecting distribution:
      • Organ blood flow
      • Plasma protein binding
      • Molecular size

    Plasma Proteins

    • Many drugs bind to plasma proteins.
    • Free drug level, not total, affects drug activity.
    • Important for highly protein-bound drugs, small volume of distribution, or drugs with low therapeutic index.

    Protein Binding Interactions

    • Interactions between a specific drug and other high-binding drug, thus resulting in decreased effect (availability) of the target drug.

    Volume of Distribution (Vd)

    • Volume of fluid needed to contain total amount of absorbed drug in the body.
    • Used to calculate loading dose.
    • Vd units are expressed as liters (L) or liters per kilogram (L/kg).
    • Higher Vd indicates greater distribution into tissues.
    • Low Vd indicates stronger plasma protein binding.

    Drug Elimination

    • Metabolism:
      • About 90% by the liver to make drugs ionized and readily excretable by kidneys.
      • Affected by hepatic or renal dysfunction; may halve drug clearance.
      • Phase I: oxidation, reduction, hydrolysis
        • Microsomal metabolism (cytochrome P450 enzymes)
      • Phase II: conjugation with endogenous compounds
        • Glucuronidation, acetylation, glutathione conjugation.
    • Non-microsomal metabolism
      • Hydrolysis: addition of water with subsequent bond breakage, e.g., amidases and esterases
      • Monoamine oxidases (MAO): metabolism of endogenous amine neurotransmitters & exogenous compounds
    • Zero-order Kinetics: constant amount of drug metabolized per unit of time.
    • First-order Kinetics: rate of drug metabolism is proportional to drug concentration.
      • Some drugs, aspirin etc, exhibit zero order kinetics while many others, using first order elimination kinetics
    • Excretion: Via kidneys, sweat, lungs (other routes)
      • Urine pH can affect excretion of weak acids and bases.
      • making urine alkaline to increase excretion of weak acids (e.g., aspirin) and acid to increase excretion of weak bases (e.g., amphetamines).

    Half-Life (t1/2)

    • Time needed to reduce plasma concentration by 50%.
    • Affected by Vd and clearance (Cl).

    Clearance (Cl)

    • Clearance rate of drug from systemic circulation (volume/time).
    • Clinically important because clearance is constant over a range of concentrations, and metabolizing enzymes and transporters are unsaturated so the rate of elimination follows first-order kinetics.

    Steady State

    • When rate of drug administration= rate of drug elimination.
    • Reaches after approximately 4-5 half-lives.
    • Independent of dosage frequency and dose amount.

    Loading Dose (LD)

    • Higher initial dose to quickly reach therapeutic plasma concentrations.
    • Calculated using Vd and bioavailability.

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