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Questions and Answers

What is the study of the actions, mechanisms, uses, and adverse effects of drugs?

  • Pharmacodynamics
  • Pharmacokinetics
  • Pharmacoepidemiology
  • Pharmacology (correct)

    • What is the risk associated with the use of any drug?

  • Pharmacodynamics
  • Adverse effects (correct)
  • Desired effects
  • Pharmacokinetics

    • What should the physician assess when deciding which drug to prescribe?

  • The balance of desired and adverse effects (correct)
  • Only the desired effects
  • Only the adverse effects
  • The cost of the drug

    • Pharmacology can be divided into how many disciplines?

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

    What is the first step in the process of pharmacokinetics?

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

    What happens to the drug during the metabolism phase?

    <p>It undergoes enzymatic alteration</p> Signup and view all the answers

    What is the definition of a drug?

    <p>A natural or synthetic substance that alters the physiological state of a living organism</p> Signup and view all the answers

    What is the purpose of using drugs?

    <p>For prevention, treatment, and diagnosis of diseases</p> Signup and view all the answers

    What determines the rate of drug absorption at any given pH?

    <p>The ratio of ionized to non-ionized forms of the drug</p> Signup and view all the answers

    What is the pH at which 50% of a drug is ionized and 50% is non-ionized?

    <p>The pKa of the drug</p> Signup and view all the answers

    What is the significance of pKa in drug absorption from the GIT?

    <p>It determines the site of drug absorption</p> Signup and view all the answers

    How can aspirin toxicity be treated?

    <p>By alkalinization of urine</p> Signup and view all the answers

    What is bioavailability?

    <p>The fraction of the administered dose of a drug that reaches the systemic circulation</p> Signup and view all the answers

    What is the oral bioavailability of a drug?

    <p>The ratio of the total amount of drug reaching the systemic circulation to the total amount of drug administered orally</p> Signup and view all the answers

    What does an oral bioavailability of 20% mean?

    <p>20% of the administered dose of the drug reaches the systemic circulation</p> Signup and view all the answers

    What is the apparent volume of distribution?

    <p>The volume of the organs and tissues that the drug is distributed to</p> Signup and view all the answers

    What is the main objective of pharmacokinetics?

    <p>To study the movement and disposition of drugs within and by the body</p> Signup and view all the answers

    What is the process of drug absorption?

    <p>The passage of drug molecules from the site of administration to the systemic circulation</p> Signup and view all the answers

    What is the effect of alkalinizing the urine on the excretion of a weak acid?

    <p>It accelerates the excretion</p> Signup and view all the answers

    What is the effect of acidifying the urine on the excretion of a weak base?

    <p>It accelerates the excretion</p> Signup and view all the answers

    Which of the following routes of administration does not require drug absorption?

    <p>Intravenous route</p> Signup and view all the answers

    What is the main factor affecting drug absorption?

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

    What is the rate of penicillin G excretion in urine per minute?

    <p>1200 mg/min</p> Signup and view all the answers

    What is the volume of plasma cleared from penicillin G per minute?

    <p>400 mL/min</p> Signup and view all the answers

    What is the relationship between molecular size and drug absorption?

    <p>Small molecules are absorbed more quickly</p> Signup and view all the answers

    What is the formula to calculate renal clearance of a drug?

    <p>Renal clearance = renal excretion rate / plasma drug concentration</p> Signup and view all the answers

    What is the effect of ionization on drug absorption?

    <p>Ionization decreases drug absorption</p> Signup and view all the answers

    What is the renal clearance of penicillin G if the renal excretion rate is 1200 mg/min and the plasma concentration is 3 mg/mL?

    <p>400 mL/min</p> Signup and view all the answers

    What is the effect of vascularity at the site of absorption on drug absorption?

    <p>Vascularity increases drug absorption</p> Signup and view all the answers

    What is the renal clearance of Drug X if 600 mL of urine was collected in one hour and the concentration of Drug X in the urine was 1 mg/mL and the mid-point plasma concentration was 0.1 mg/mL?

    <p>60 mL/min</p> Signup and view all the answers

    What is the term for the process by which the body removes drugs and their metabolites?

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

    What is the unit of renal clearance?

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

    What is the time required for complete drug elimination?

    <p>5 t1/2</p> Signup and view all the answers

    What is the definition of steady state plasma concentration (Cpss)?

    <p>The steady level of drug in plasma when rate of drug administration equals rate of drug elimination</p> Signup and view all the answers

    When is the Cpss reached?

    <p>After 5 t1/2</p> Signup and view all the answers

    What is the relationship between the rate of drug administration and the rate of drug elimination at Cpss?

    <p>The rate of drug administration is equal to the rate of drug elimination</p> Signup and view all the answers

    What is the abbreviation for elimination half-life?

    <p>t1/2</p> Signup and view all the answers

    What is the significance of 5 t1/2 in pharmacology?

    <p>It is the time required for complete drug elimination</p> Signup and view all the answers

    What is the definition of elimination half-life (t1/2)?

    <p>The time required for the concentration of the drug to decrease by half</p> Signup and view all the answers

    What is the relationship between the rate of drug administration and the rate of drug elimination at steady state?

    <p>The rate of drug administration is equal to the rate of drug elimination</p> Signup and view all the answers

    Study Notes

    Pharmacokinetics

    • Pharmacology is the study of the actions, mechanisms, uses, and adverse effects of drugs.
    • A drug is any natural or synthetic substance that alters the physiological state of a living organism.
    • Pharmacology can be divided into two disciplines: pharmacokinetics and pharmacodynamics.

    Pharmacokinetics

    • Pharmacokinetics is the branch of pharmacology that studies the movement and disposition of drugs within and by the body.
    • It includes:
      • Drug absorption
      • Distribution
      • Metabolism
      • Excretion

    Drug Absorption

    • Definition: passage of drug molecules from the site of administration to the systemic circulation.
    • Applies to all routes of administration, except for topical and intravenous routes.
    • Requires the drug to cross one or more layers of plasma membranes.
    • Factors affecting absorption:
      • Molecular size: small molecules are absorbed faster than large molecules.
      • Dose and concentration of the drug: absorption increases with increasing dose (up to a limit).
      • Lipid solubility: ionization of the drug affects its ability to cross biological membranes.
      • Route of administration: IM route is faster than oral route.
      • Integrity of the absorbing surface: ischemia decreases absorption.
      • Vascularity at the site of absorption: affects the rate of absorption.

    pKa and Drug Ionization

    • Most drugs are weak acids or bases that exist in both ionized and nonionized forms.
    • Only nonionized form (nonpolar) of the drug is lipid soluble and can cross biological membranes.
    • Ionized form (polar) of the drug is non-lipid soluble (water soluble) and cannot cross biological membranes.
    • The pKa of a drug determines the ratio between the two forms and affects the rate of drug absorption.
    • Clinical significance of pKa:
      • Site of drug absorption from the GIT: aspirin is a weak acid that becomes nonionized and more absorbable in the stomach (pH = 1.5).
      • Drug excretion by the kidney: aspirin toxicity can be treated by alkalinization of urine, and amphetamine toxicity can be treated by acidification of urine.

    Bioavailability

    • Definition: the fraction of the administered dose of a drug that reaches the systemic circulation.
    • Intravenously administered drug has 100% bioavailability.
    • Oral bioavailability of a drug can be calculated using the formula: (total amount of drug reaching circulation / total amount of drug administered) × 100.

    Apparent Volume of Distribution (Vd)

    • Definition: the volume of fluid that would be required to contain the total amount of drug in the body at the same concentration as found in the plasma.
    • Drugs are distributed to organs and tissues via the circulation, diffusing from the blood to the interstitial fluid and into the cells.

    Elimination Half-Life (t1/2)

    • Definition: the time required for the plasma concentration of a drug to decrease by one-half.
    • Steady-state plasma concentration (Cpss) is reached after 5 t1/2.
    • Cpss is the steady level of drug in plasma achieved when the rate of drug administration equals the rate of drug elimination.

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