Pharmacology: Drug Absorption and Distribution
21 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which factor has the greatest impact on the rate of drug absorption when comparing different administration routes?

  • The solubility of the drug
  • The thickness of tissue
  • The blood supply at the site of administration (correct)
  • The formulation of the drug

    • How does a drug's solubility affect its absorption?

  • Higher solubility allows it to cross the plasma membrane easily. (correct)
  • Lower solubility results in a faster absorption.
  • Solubility has no effect on absorption.
  • Drugs must be solid to be absorbed.

    • What is the primary benefit of intravascular drug administration?

  • It is always less expensive than oral administration.
  • It requires less precise dosing.
  • It provides a longer duration of action.
  • It bypasses absorption barriers. (correct)

    • Which of the following descriptions best explains why absorption is faster through the small intestine compared to the skin?

    <p>There is only a single layer of epithelial cells in the small intestine.</p> Signup and view all the answers

    Which condition could potentially slow down the absorption rate of a drug in a subcutaneous injection?

    <p>Presence of cardiovascular disease</p> Signup and view all the answers

    Which type of drugs can pass through the plasma membrane via simple diffusion?

    <p>Lipid-soluble drugs</p> Signup and view all the answers

    What primarily affects the pharmacological action of a drug after entering systemic circulation?

    <p>The proportion of unbound drug in circulation</p> Signup and view all the answers

    Which barrier provides protection to the CNS from harmful substances?

    <p>Blood-brain barrier</p> Signup and view all the answers

    What factor does NOT affect the distribution of a drug within the body?

    <p>Age of the patient</p> Signup and view all the answers

    Which of the following describes how water-soluble drugs typically cross plasma membranes?

    <p>Through facilitated diffusion or active transport</p> Signup and view all the answers

    What type of tissues are drugs likely to distribute to more slowly?

    <p>Poorly perfused tissues like adipose tissue</p> Signup and view all the answers

    What factor can limit drug distribution across the placental barrier?

    <p>Molecular weight of the drug</p> Signup and view all the answers

    The permeability of which type of tissue barriers can significantly influence drug absorption?

    <p>Brain tissue barriers</p> Signup and view all the answers

    What is primarily responsible for the irreversible loss of a drug from the plasma?

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

    Which of the following factors can influence the process of renal excretion of drugs?

    <p>Urinary pH</p> Signup and view all the answers

    Which route is primarily used by the body for the excretion of volatile substances?

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

    What percentage of the original drug dose ultimately reaches systemic circulation after absorption and metabolism?

    <p>20%</p> Signup and view all the answers

    Which factor does NOT play a role in the reabsorption of lipid-soluble drugs in the kidneys?

    <p>Drug volume in plasma</p> Signup and view all the answers

    What term describes the range of drug concentration offering therapeutic effects while minimizing toxicity?

    <p>Therapeutic window</p> Signup and view all the answers

    Which of the following is a primary site for drug excretion from the body?

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

    How does the solubility of a drug primarily affect its absorption?

    <p>Lipid soluble drugs are absorbed more rapidly than water-soluble drugs.</p> Signup and view all the answers

    Study Notes

    Drug Absorption

    • Drugs are absorbed from the site of administration into the bloodstream.
    • The rate of absorption depends on various factors, including:
      • Drug solubility (lipid-soluble drugs are absorbed faster)
      • Route of administration – oral vs. intravenous
      • Tissue surface area and thickness
      • Blood supply at the site of administration
    • Example:
      • A patient takes a 100mg dose of a drug
      • 80 mg of the dose is absorbed from the small intestine and reaches the liver via the hepatic portal vein → 20 mg was not absorbed from the small intestine
      • The liver then metabolises the remaining 80 mg → 60 mg is irreversibly lost (eliminated)
      • Only 20 % of the original dose reaches the systemic circulation
      • The amount of drug that reaches systemic circulation is known as the BIOAVAILABILITY of the drug

    Drug Distribution

    • The drug is distributed to various body compartments after reaching the systemic circulation.
    • Distribution depends on:
      • Drug solubility
      • Cardiovascular functioning
      • Perfusion of the area
      • Degree of blood flow
      • The permeability of the capillaries
      • pH of the area
      • Binding of drug to plasma proteins
    • Barriers to drug distribution:
      • Blood-brain barrier
      • Placental barrier
    • Intravascular administration:
      • Intravenous and intra-arterial routes bypass absorption
      • Drugs are immediately distributed around the body.
      • Medication (tablet) taken orally must disintegrate, dissolve, and be absorbed from the small intestine into the hepatic portal system before entering the systemic circulation.

    Drug Elimination

    • The pharmacological effects of a drug continue until it is removed from the body.
    • Elimination is the irreversible loss of the drug from the plasma, which occurs through metabolism and excretion.
    • The liver is the primary site of elimination due to metabolism.
    • Excretion is the irreversible loss of the drug from the body:
      • Kidneys excrete most drugs and their metabolites
      • Drugs can be eliminated in bile and removed from the body in faeces
      • Lungs are the primary route for excretion of volatile substances like inhalation anaesthetics
      • Other routes include intestine, salivary, sweat and mammary glands

    Renal Excretion

    • Kidneys are the main site of drug excretion from the body.
    • Free unbound drug can be filtered from the blood into the renal filtrate.
    • Lipid-soluble drugs may be reabsorbed from the renal filtrate back into systemic circulation.
    • Water-soluble drugs can also be secreted from the blood into the filtrate.
    • The process of excretion is dependent on:
      • Urinary pH
      • Renal function
      • Cardiovascular function

    Pharmacokinetics - How the Body Affects the Drug

    • Pharmacokinetics describes how the body absorbs, distributes, metabolizes, and excretes drugs.
    • It is essential for understanding how a drug will act within the body and for determining the most appropriate dosage.

    Rational Drug Use: Dosage Regime Development

    • The therapeutic range is the concentration of a drug that has a high probability of producing the desired therapeutic effect with a low probability of toxic effects.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Pharmacology PDF

    Description

    This quiz covers key concepts in pharmacology related to drug absorption and distribution. Learn how various factors influence the bioavailability of drugs and their subsequent distribution throughout the body. Test your understanding of the mechanisms behind these vital pharmacokinetic processes.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser