Pharmacy Preboard Review: Drug Receptors
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Questions and Answers

What determines the necessity, route, and extent of metabolism?

  • Chemical structure of the drug (correct)
  • Type of metabolic enzyme
  • Drug dosage
  • Physiologic or disease state
  • What happens to drug concentrations when the drug dosage is increased?

  • They decrease
  • They become unpredictable
  • They increase (correct)
  • They remain the same
  • What can be affected by pathologic factors that alter liver function?

  • Hepatic clearance (correct)
  • Cardiac output
  • Metabolic enzyme activity
  • Renal clearance
  • What is a result of congestive heart failure?

    <p>Decreased hepatic blood flow</p> Signup and view all the answers

    What is a factor that influences drug metabolism?

    <p>Physiologic or disease state</p> Signup and view all the answers

    What can be saturated by increased drug concentrations?

    <p>Metabolic enzymes</p> Signup and view all the answers

    What happens to the fraction of unbound drug when albumin production decreases?

    <p>The fraction of unbound drug increases.</p> Signup and view all the answers

    What determines the acetylation rate?

    <p>The amount of N-acetyltansferase present</p> Signup and view all the answers

    Who is more prone to hepatoxicity from isoniazid?

    <p>Fast acetylators</p> Signup and view all the answers

    What is the effect of a low protein diet on oxidative drug metabolism capacity?

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

    What can lead to a deficiency of certain amino acids?

    <p>Low protein diet</p> Signup and view all the answers

    What can affect the fraction of unbound drug?

    <p>Albumin production</p> Signup and view all the answers

    What is the primary function of esterases in plasma?

    <p>To hydrolyze esters</p> Signup and view all the answers

    Where does the first-pass metabolism of drugs administered intravenously occur?

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

    What is the primary function of nasal mucosa in drug metabolism?

    <p>To metabolize drugs using CYP450 enzymes</p> Signup and view all the answers

    What is the primary function of placental metabolism?

    <p>To transport drugs from the maternal to the fetal circulation</p> Signup and view all the answers

    What is a strategy to manage drug metabolism?

    <p>Using a different dosage form to avoid rapid metabolism</p> Signup and view all the answers

    What is a site of extrahepatic metabolism?

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

    What is a portal of entry for drugs?

    <p>GI mucosa</p> Signup and view all the answers

    What is a portal of excretion for drugs?

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

    Where are drug receptors typically located?

    <p>Embedded within the cell membrane</p> Signup and view all the answers

    What is the primary function of a drug receptor?

    <p>Exert the characteristic effects of a drug</p> Signup and view all the answers

    What is another term for drug receptor interactions?

    <p>Ligand-receptor interactions</p> Signup and view all the answers

    What is the significance of specific regions on a receptor?

    <p>They interact with complementary functional groups of drugs</p> Signup and view all the answers

    What is the term for a molecule that binds to a receptor?

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

    What is the primary mechanism by which receptors are activated?

    <p>Binding of a ligand</p> Signup and view all the answers

    What is the primary purpose of administering carbidopa along with levodopa?

    <p>To prevent the peripheral formation of dopamine</p> Signup and view all the answers

    Which enzyme is primarily responsible for the Phase I metabolism of drugs?

    <p>Cytochrome P-450</p> Signup and view all the answers

    What mechanism do beta-lactamase inhibitors utilize to combat antibiotic resistance?

    <p>They inhibit the action of beta-lactamase enzymes</p> Signup and view all the answers

    Which of the following is an example of a Phase II metabolism enzyme?

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

    Which component is not typically involved in the metabolism of levodopa?

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

    Which of the following statements about beta-lactam antibiotics is incorrect?

    <p>They are effective against all bacteria.</p> Signup and view all the answers

    What function does glucuronyl transferase serve in drug metabolism?

    <p>Conjugation of drugs with glucuronic acid</p> Signup and view all the answers

    Why is it important to block peripheral metabolism of levodopa?

    <p>To ensure adequate concentrations reach the CNS</p> Signup and view all the answers

    Study Notes

    Drug Receptors

    • A protein molecule embedded in the cell membrane with part of its structure exposed on the outside of the cell, where the drug exerts its characteristic effects.
    • Contains specific regions that react with complementary functional groups.
    • Also referred to as Ligand-Receptor Interactions.

    Receptor Activation

    • The process by which receptors are activated, leading to a response.

    Factors Influencing Drug Metabolism

    • Chemical structure: the presence or absence of functional groups determines the necessity, route, and extent of metabolism.
    • Drug dosage: increased dosage can saturate metabolic enzymes, leading to increased drug concentrations.
    • Physiologic or disease state: pathologic factors that alter liver function can affect a drug's hepatic clearance.
    • Genetic variation: acetylation rate depends on the amount of N-acetyltransferase present.
    • Nutritional status: low protein diet can lead to deficiency of certain amino acids, decreasing oxidative drug metabolism capacity.

    Metabolism Sites

    • Liver: primary site of drug metabolism.
    • Plasma: contains esterases responsible for hydrolysis of esters.
    • Intestinal mucosa: lipid-soluble drugs are metabolized into polar or inactive metabolites before entering the blood.
    • Nasal mucosa: provides a high level of CYP450 activity, altering the amount of drug that reaches the systemic circulation.
    • Lung: responsible for first-pass metabolism of drugs administered intravenously, intramuscularly, transdermally, or subcutaneously.
    • Placenta and fetus: drugs in their active form in the maternal circulation pass unchanged into the fetal circulation.

    Strategies to Manage Drug Metabolism

    • Pharmaceutical strategies: involve the use of different dosage forms to either avoid or compensate for rapid metabolism.
    • Decreasing the overall extent of metabolism and increasing the duration of action.

    Examples of Strategies to Manage Drug Metabolism

    • Levodopa: concurrent administration of carbidopa prevents peripheral formation of dopamine, ensuring adequate concentrations of L-dopa reach the CNS.
    • Beta-lactam antibiotics: beta-lactamase inhibitor (clavulinic acid) is used in conjunction with a penicillin (amoxicillin) to treat infections.

    Enzymes Catalyzing Phase I Metabolism

    • Cytochrome P-450
    • Aldehyde and alcohol dehydrogenase
    • Deaminases
    • Esterases
    • Amidases
    • Epoxide hydratases

    Enzymes Catalyzing Phase II Metabolism

    • Glucuronyl transferase (glucuronide conjugation)
    • Sulfotransferase (sulfate conjugation)
    • Transacylases (amino acid conjugation)
    • Acetylases
    • Ethylases
    • Methylases
    • Glutathione transferase

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