Pharmacology Drug Clearance Quiz
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Questions and Answers

What is the term used for the clearance of a drug that is removed from the blood by renal excretion?

  • Systemic clearance
  • Hepatic clearance
  • Renal clearance (correct)
  • Metabolic clearance

    • The liver is solely responsible for the process of renal clearance.

    False

    What does systemic clearance refer to?

    The sum of all individual organ clearances that contribute to the overall elimination of drugs.

    A small clearance and a large volume of distribution will promote ______ elimination and a ______ half-life.

    <p>slow; long</p> Signup and view all the answers

    Which of the following statements about clearance is TRUE?

    <p>A higher clearance indicates a more efficient eliminating organ.</p> Signup and view all the answers

    What is the primary process through which drugs are eliminated from the body?

    <p>Metabolism and excretion</p> Signup and view all the answers

    Match the following clearance types with their correct definitions:

    <p>Renal clearance = Clearance of drug removed via kidney excretion Metabolic clearance = Clearance of drug removed via metabolism Hepatic clearance = Clearance of drug removed by hepatic metabolism Systemic clearance = Total body clearance sum of all organ clearances</p> Signup and view all the answers

    Name the two principal organs responsible for drug elimination.

    <p>Kidney and liver</p> Signup and view all the answers

    Elimination of drugs primarily occurs via first-order processes for all drugs.

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

    Clearance remains constant as long as the rate of drug elimination is a first-order process.

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

    What is the term for the time interval required to eliminate 50% of the amount of drug in the body?

    <p>Elimination half-life</p> Signup and view all the answers

    The process of conversion of one chemical species to another is called ________.

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

    Match the following terms with their definitions:

    <p>Elimination = Irreversible loss of drug from systemic circulation Clearance = Volume of plasma from which drug is eliminated per unit time Excretion = Loss of unchanged drug in urine, bile, or feces Metabolism = Conversion of one chemical species to another</p> Signup and view all the answers

    Which of the following equations represents the relationship between the elimination rate and drug concentration?

    <p>All of the above</p> Signup and view all the answers

    What is the unit of clearance commonly expressed in?

    <p>mL/min or L/h</p> Signup and view all the answers

    The elimination rate is the sum of metabolism rate and excretion rate.

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

    What is the approximate volume of blood the kidneys receive per minute?

    <p>1.2–1.5 L</p> Signup and view all the answers

    Blood cells can pass through the glomerular membrane during filtration.

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

    What is the measured rate of glomerular filtration known as?

    <p>Glomerular Filtration Rate (GFR)</p> Signup and view all the answers

    Drugs that are ___ bound to plasma proteins cannot be filtered through the glomerulus.

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

    What drug is often used to measure the Glomerular Filtration Rate (GFR)?

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

    Match the following substances with their filtration characteristics:

    <p>Inulin = Measured to evaluate GFR Plasma proteins = Cannot pass through glomerular membrane Small drugs = Readily filtered from blood Blood cells = Too large to be filtered</p> Signup and view all the answers

    A drug that is 70% bound to plasma proteins will have its clearance equal to the GFR.

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

    If the GFR is 120 ml/min and a drug is 30% free, its clearance would be ___ ml/min.

    <p>36</p> Signup and view all the answers

    Which process is commonly seen with endogenous substances or nutrients that the body needs to conserve?

    <p>Active Tubular Reabsorption</p> Signup and view all the answers

    If a drug is completely reabsorbed, the clearance of the drug is equal to the GFR of 120 mL/min.

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

    What factors contribute to the appearance of a drug in the urine?

    <p>Filtration, secretion, and reabsorption.</p> Signup and view all the answers

    Lipid-soluble drugs are reabsorbed from the lumen primarily during __________ tubular reabsorption.

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

    Match the following renal clearance terms with their definitions:

    <p>GFR = Rate of filtration at the glomerulus Clearance (Clr) = Measure of renal excretion Ku = Urinary excretion rate constant V = Apparent volume of distribution</p> Signup and view all the answers

    What is the impact of reabsorption on the half-life of a drug?

    <p>Increases the half-life</p> Signup and view all the answers

    How much must tubular reabsorption exceed tubular secretion to maintain proper clearance according to the content provided?

    <p>70 mL/min</p> Signup and view all the answers

    The renal clearance of a drug can be estimated using the formula where _______ is the mass of drug excreted in urine.

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

    What process requires energy input for drug transport during renal excretion?

    <p>Active tubular secretion</p> Signup and view all the answers

    Active tubular secretion is highly specific for the substances being secreted.

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

    Name a drug that is transported by the organic anion transporter during active tubular secretion.

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

    The process of __________ allows for the reabsorption of water into the systemic circulation in the kidneys.

    <p>tubular re-absorption</p> Signup and view all the answers

    How does protein binding affect the elimination of drugs excreted by active secretion?

    <p>It has very little effect on elimination.</p> Signup and view all the answers

    What happens to lipophilic drugs during tubular re-absorption?

    <p>They are reabsorbed back into circulation.</p> Signup and view all the answers

    Match the following transport processes with their characteristics:

    <p>Glomerular filtration = Passive process influenced by blood concentration Active tubular secretion = Requires energy and carriers for transport Tubular re-absorption = Water and substances are returned to circulation Organic anion transporter = Transports organic acids like penicillins</p> Signup and view all the answers

    As the filtrate moves through the distal tubule, approximately __________ of filtered water has been reabsorbed.

    <p>80%</p> Signup and view all the answers

    What occurs when urine pH is acidic for weak acids?

    <p>Weak acids exist in their non-ionized form and are reabsorbed.</p> Signup and view all the answers

    Sodium bicarbonate injection is used to treat overdosing with weak bases.

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

    What is the role of hemodialysis?

    <p>To remove toxic waste material from the blood.</p> Signup and view all the answers

    Ammonium chloride injection ________ urine pH and promotes ionization of weak bases.

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

    Match the drugs with their case for intervention in overdose:

    <p>Phenobarbital = Sodium bicarbonate injection Codeine = Ammonium chloride injection Aspirin = Sodium bicarbonate injection Amphetamine = Ammonium chloride injection</p> Signup and view all the answers

    Which factors can affect renal clearance?

    <p>All of the above</p> Signup and view all the answers

    What size of molecules is particularly important for removal during hemodialysis?

    <p>Small molecules less than 500 molecular weight.</p> Signup and view all the answers

    Lipid-soluble drugs have a fast renal clearance.

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

    Study Notes

    Drug Excretion

    • Drug excretion is the irreversible loss of a drug from the systemic circulation through metabolism and/or excretion.
    • Elimination of drugs occurs via metabolism or excretion, or both.
    • Metabolism is the process of converting one chemical species to another chemical species.
    • Excretion is the irreversible loss of the unchanged form of the drug in urine, bile, feces, and other body fluids.

    Elimination Rate

    • Renal excretion and metabolism are primarily first-order processes for over 90% of drugs.
    • Elimination not following first-order kinetics results in nonlinear pharmacokinetics.
    • Elimination rate is the amount of a drug eliminated in a unit time.
    • First-order elimination rate equation: -dX/dt = KX
      • (-dX/dt) represents the rate of drug decrease in the body over time.
      • K represents the first-order elimination rate constant.
      • X represents the amount of drug in the body at time t.
    • Elimination rate of a drug at any time depends on:
      • The elimination rate constant.
      • The amount of drug in the body.

    Elimination Half-Life

    • Elimination half-life (t1/2) is the time interval required to eliminate 50% of the drug present in the body at the beginning of the interval.
    • Equation for elimination half-life: t1/2 = 0.693/K.

    Clearance Definitions

    • Clearance is a fundamental, independent pharmacokinetic parameter for elimination.
    • It's a proportionality constant describing the relationship between the rate of elimination and plasma concentration.
    • Clearance is expressed as a volume of plasma containing drug eliminated per unit time.
    • The units for clearance are typically mL/min or L/h.
    • Clearance is the most useful pharmacokinetic parameter for evaluating the elimination mechanism and eliminating organs (kidney and liver). A larger clearance indicates a more efficient eliminating organ.

    Renal Clearance

    • Renal clearance (ClR) is the clearance of a drug that is removed from the blood by renal excretion.
    • Renal excretion is the removal of a drug, or its metabolites, from the blood in chemically unchanged form.
    • The kidney is the major excretory organ for removing metabolic wastes and maintaining fluid and electrolyte balance.
    • The kidney consists of functional units called nephrons.

    Renal Excretion Processes

    • The kidney's nephrons have three main processes: glomerular filtration, active tubular secretion, and passive tubular reabsorption.
    • Glomerular filtration is a unidirectional process where small molecules (including many drugs) are filtered into the renal tubule. Larger molecules and plasma proteins typically aren't filtered.
    • Active tubular secretion actively transports drug molecules against a concentration gradient into the tubular fluid, usually requiring energy.
    • Passive tubular reabsorption passively returns lipid-soluble drug molecules back into the blood.
    • The net result of these processes determines a drug's appearance in the urine.
      • Rate of excretion = Rate of filtration + Rate of secretion - Rate of reabsorption
        • ClR = Filtration rate + Secretion rate - Reabsorption rate

    Factors Affecting Renal Clearance

    • Kidney perfusion: Kidney blood flow is crucial for active secretion and glomerular filtration. Reduced blood flow slows renal clearance which is affected by age or diseases.
    • Renal activity: Lower renal activity results in slower renal clearance, common in newborns, elderly and those with kidney disease.
    • Drug molecular size: Small molecules (<500) are more easily cleared by the kidneys than larger ones.
    • Protein binding: Drugs highly bound to plasma proteins have slower renal clearance as only the unbound portion is filtered. Active tubular secretion is more efficient for some of these drugs.
      • Some drugs (e.g. probenecid) competitively inhibit the tubular secretion of other drugs.
    • Urine pH: Urine pH influences renal clearance of weak electrolytes, impacting the ionization and reabsorption of weak acids and bases. - Drug Lipid Solubility: Lipid-soluble drugs have slower renal clearance due to their reabsorption in the distal tubules by passive diffusion.
    • Solute Concentration in Urine: Fluid intake impacts solute concentration, affecting tubular reabsorption, and renal clearance.

    Hemodialysis

    • Hemodialysis ('artificial kidney') is a procedure used to remove toxic wastes from the blood in renal failure, when the kidneys can't perform this function adequately.
    • During hemodialysis, blood is passed externally through a semi-permeable membrane immersed in an aqueous, isotonic solution.
    • Small molecules (including nitrogenous wastes and some drugs) diffuse from the blood across the membrane into the solution, thus being eliminated.
    • This technique is especially helpful for drugs with small molecular weights, not tightly bound to plasma proteins, low apparent volume of distribution, or good water solubility.

    Measurement of Renal Clearance

    • Renal clearance can be calculated from urine and plasma data to understand a drug's elimination.
    • The calculation (ClR) involves collecting urine samples over a defined period and measuring the drug concentration in the samples.
    • The volume of urine collected and the concentration of the drug measured are used along with data of plasma drug concentration to calculate renal clearance using the formula, ClR= (Rate of excretion) / (Plasma Drug Concentration).

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    Drug Excretion PDF

    Description

    Test your knowledge on drug clearance processes, renal excretion, and the roles of the liver and kidneys in drug elimination. This quiz covers key concepts such as systemic clearance, first-order processes, and definitions related to pharmacology. Perfect for students studying pharmacology or medicine.

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