Introduction to Pharmacokinetics
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Questions and Answers

What is the primary characteristic of bound drugs?

  • They can easily pass through biological membranes.
  • They can produce biological effects.
  • They undergo rapid metabolism in the liver.
  • They are not available for distribution. (correct)

    • Which plasma protein do acidic drugs primarily bind to?

  • Alpha 1 acid glycoprotein
  • Fibrinogen
  • Albumin (correct)
  • Globulin

    • How do free drugs differ from bound drugs in pharmacokinetics?

  • Free drugs cannot bind to receptors.
  • Free drugs have a high molecular weight.
  • Free drugs can produce biological effects. (correct)
  • Free drugs cannot undergo elimination.

    • What is the main factor determining the binding of drugs to plasma proteins?

    <p>The type of drug's acidity or basicity</p> Signup and view all the answers

    What best describes temporary reservoir sites in pharmacokinetics?

    <p>They are not permanent storage sites.</p> Signup and view all the answers

    Which type of drugs primarily bind to alpha 1 acid glycoprotein?

    <p>Weakly basic drugs</p> Signup and view all the answers

    What implication does plasma protein binding have on a drug's pharmacodynamics?

    <p>It prevents the drug from binding to target receptors.</p> Signup and view all the answers

    What effect does strong affinity of a drug towards its binding protein have on its availability?

    <p>Decreases the drug's availability for action.</p> Signup and view all the answers

    How does extensive plasma protein binding affect drug concentration?

    <p>It decreases the free drug concentration.</p> Signup and view all the answers

    What is the primary factor influencing the need for dosing adjustments?

    <p>Alterations in plasma protein binding.</p> Signup and view all the answers

    What is a consequence of high plasma protein binding in patients with altered PPB?

    <p>Increased risk of drug toxicity.</p> Signup and view all the answers

    What condition can lead to hypoalbuminemia?

    <p>Acute renal failure.</p> Signup and view all the answers

    Which of these drugs is likely to require a dose adjustment when there is hypoalbuminemia?

    <p>Highly protein bound drugs.</p> Signup and view all the answers

    In which scenario would a physician most likely consider drug toxicity risk due to PPB alterations?

    <p>A patient with cirrhosis.</p> Signup and view all the answers

    What effect does increased free drug concentration have on drug dosing?

    <p>It can lead to harmful side effects without adjustments.</p> Signup and view all the answers

    What is the primary function of drug metabolizing enzymes in the liver?

    <p>Convert drugs into more water-soluble substances</p> Signup and view all the answers

    Which of the following is true regarding the CYP-450 enzyme system?

    <p>These enzymes are involved in the metabolism of the majority of drugs</p> Signup and view all the answers

    How can inflammation affect plasma protein binding of drugs?

    <p>It can either increase or decrease plasma protein binding.</p> Signup and view all the answers

    What effect does enzyme induction have on drug metabolism?

    <p>Increases the metabolism rate of drugs</p> Signup and view all the answers

    What is the outcome of enzyme inhibition on drug metabolism?

    <p>It prolongs the half-life of drugs</p> Signup and view all the answers

    What happens to the rate of drug elimination when the plasma concentration decreases?

    <p>The rate of elimination decreases.</p> Signup and view all the answers

    Which drug is known to induce CYP enzymes affecting drug metabolism?

    <p>Rifampicin</p> Signup and view all the answers

    What defines the steady state concentration of a drug?

    <p>When drug administration and elimination rates are equal.</p> Signup and view all the answers

    Why do quaternary ammonium compounds not require metabolism in the liver?

    <p>They are already water-soluble</p> Signup and view all the answers

    Which statement best describes the plasma half-life of ethanol?

    <p>It varies and depends on the individual metabolic rate.</p> Signup and view all the answers

    Which of the following is a consequence of CYP gene polymorphism?

    <p>Variability in drug metabolism among individuals</p> Signup and view all the answers

    What complication can arise from enzyme inhibition in drug interactions?

    <p>Unpredictable drug toxicity</p> Signup and view all the answers

    Why is the steady state concentration especially important for drugs with a low margin of safety?

    <p>It ensures that there is a constant level of drug without toxicity.</p> Signup and view all the answers

    At what point is the steady state concentration typically reached?

    <p>After the fourth or fifth half-life.</p> Signup and view all the answers

    Which factor is NOT associated with reaching a steady state concentration of drugs?

    <p>The body temperature of the patient.</p> Signup and view all the answers

    What happens when the inputs and outputs of a drug in the body are not equal?

    <p>The patient may experience acute toxicity or reduced drug effect.</p> Signup and view all the answers

    What is the primary structural difference between typical capillaries and blood brain capillaries?

    <p>Blood brain capillaries have tight junctions between endothelial cells.</p> Signup and view all the answers

    What is the pharmacological significance of maintaining a constant drug concentration in the body?

    <p>It prevents acute toxicity and maintains drug effects.</p> Signup and view all the answers

    Which substances can easily cross the blood brain barrier under normal conditions?

    <p>Lipid soluble and unionized molecules.</p> Signup and view all the answers

    In what situation might the blood brain barrier be compromised?

    <p>In cases of brain infections like meningitis.</p> Signup and view all the answers

    What role does the placental barrier serve in pregnancy?

    <p>Prevents harmful substances while regulating gases and nutrients.</p> Signup and view all the answers

    Why do gynecologists avoid prescribing certain medications during pregnancy?

    <p>To prevent harmful effects on the developing fetus.</p> Signup and view all the answers

    What characteristic determines a drug's apparent volume of distribution (aVd)?

    <p>The drug's lipid solubility and plasma protein binding.</p> Signup and view all the answers

    Which type of drugs typically has a low volume of distribution?

    <p>Highly bound drugs with significant plasma protein interaction.</p> Signup and view all the answers

    Which of the following drugs is unable to cross the blood brain barrier under normal conditions?

    <p>Penicillin under normal physiological conditions.</p> Signup and view all the answers

    What is the main reason why proteins with a large molecular weight cannot penetrate the basement membrane?

    <p>They undergo a high degree of ionization.</p> Signup and view all the answers

    What does the formula aVd = Dose/Concentration (plasma) help calculate?

    <p>The apparent volume of distribution.</p> Signup and view all the answers

    Which of the following drugs has a low apparent volume of distribution?

    <p>Warfarin</p> Signup and view all the answers

    What is the consequence of a drug with a high volume of distribution during an overdose?

    <p>Removal of the drug from tissue is impossible.</p> Signup and view all the answers

    In the context of drug dosing, what does 'loading dose' refer to?

    <p>The single largest dose to saturate binding sites.</p> Signup and view all the answers

    Which factors affect the apparent volume of distribution?

    <p>Molecular size &amp; weight, lipid solubility, and degree of ionization.</p> Signup and view all the answers

    Why is hemodialysis a significant procedure in drug poisoning cases?

    <p>It helps filter waste products and excess fluids.</p> Signup and view all the answers

    What is the significance of saturating binding sites with a loading dose?

    <p>It allows both bound and free drugs to exert pharmacological effects.</p> Signup and view all the answers

    Study Notes

    Introduction to Pharmacokinetics

    • Pharmacokinetics is the study of how drugs move through the body
    • It involves four key processes: ADME
      • Absorption
      • Distribution
      • Metabolism
      • Excretion

    ADME Details

    • Absorption: Process of drug entering the bloodstream from the site of administration

    • Distribution: Process of drug distributing from the bloodstream to tissues/organs

    • Metabolism: Process of drug breakdown / transformation in the body

    • Excretion: Process of drug removal from the body.

    Plasma Protein Binding

    • Plasma protein binding (PPB) occurs when drugs bind to plasma proteins (primarily albumin and α1-acid glycoprotein)
    • Bound drugs are unavailable for distribution, metabolism, or elimination
    • Free drugs are available for distribution, metabolism, and elimination
    • Acidic drugs bind to albumin
    • Basic drugs bind to alpha-1 acid glycoprotein
    • Affects both pharmacokinetics and pharmacodynamics of drugs
    • Important clinical implications for dosing adjustments, particularly in patients with altered PPB (e.g., renal or hepatic issues)

    Physiological Barriers

    • Blood-brain barrier: Tight junctions between endothelial cells, limits drug entry into the brain

    • Placental barrier: Separates maternal and fetal blood, restricts drug passage to the fetus

    Volume of Distribution

    • Apparent volume of distribution (Vd): Hypothetical volume in which a drug could be distributed to achieve the same plasma concentration
    • Vd values reflect drug distribution between the plasma and tissues.
      • Low Vd: Mostly distributed in blood
      • High Vd: More widely distributed through tissues
    • Factors affecting Vd: molecular weight, lipid solubility, protein binding, ionization state, and disease states

    Drug Metabolism (Biotransformation)

    • Phase I reactions: Enzyme-catalyzed chemical transformation of drugs from nonpolar to more polar compounds (e.g., oxidation, reduction, hydrolysis)
    • Phase II reactions: Conjugation of the Phase I metabolites with endogenous substrates (e.g., glucuronidation) to further enhance water solubility for excretion.

    Drug Excretion

    • Renal excretion: Major route; involves glomerular filtration, passive tubular reabsorption, and active tubular secretion
    • Biliary excretion: Conjugated drug metabolites in bile are excreted in feces, with enterohepatic circulation
    • Other minor routes: lungs, skin, breast milk, tears, saliva

    Plasma Half-life

    • Time taken for plasma concentration to decrease by 50%.
    • Important for determining dosing intervals and drug duration of action
    • Affects attainment of steady state

    Drug Clearance

    • Volume of blood cleared of the drug per unit time; reflects elimination rate.
    • For drugs with first-order kinetics, clearance is constant

    Rate and Patterns of drug elimination

    • Drugs can be eliminated from the body exponentially (first order) or as a constant rate (zero order).
    • First order is directly related to plasma concentration
    • Zero order is independent of plasma concentration

    Steady State

    • Steady state concentration (Css): Achieved when the rate of drug intake equals the rate of drug elimination.
    • Css is important as it helps to avoid toxic concentrations or the loss of therapeutic efficacy.

    Clinical Significance of Pharmacokinetics

    • Dose adjustments are often necessary in patients with altered pharmacokinetic parameters.
    • The rate is affected by a number of factors such as age.

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    Description

    This quiz explores the fundamental concepts of pharmacokinetics, focusing on the key processes of ADME: Absorption, Distribution, Metabolism, and Excretion. Additionally, it delves into plasma protein binding and its impact on drug behavior in the body. Test your knowledge on how these processes affect the pharmacokinetics and pharmacodynamics of drugs.

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