Pharmacology Drug Interaction Quiz
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Questions and Answers

Which of the following factors increases the risk of drug interactions due to a small therapeutic window?

  • Single drug therapy
  • Low protein-binding
  • Young age
  • Impaired renal or liver function (correct)

    • What is a potential consequence of altered gastrointestinal pH on drug absorption?

  • Increased protein binding
  • Altered extent of drug ionization (correct)
  • Enhanced drug metabolism
  • Decreased formation of drug chelates

    • Which mechanism of pharmacokinetic interaction involves the transport of drugs within the body?

  • Altered GIT motility
  • Drug absorption changes
  • Drug displacement (correct)
  • Altered drug metabolism

    • Which of the following statements is true regarding absorption interactions?

    <p>They can be caused by the formation of drug chelates.</p> Signup and view all the answers

    In which patient population is the risk of beneficial drug interactions particularly high due to polypharmacy?

    <p>Elderly patients</p> Signup and view all the answers

    Which drug interaction is characterized by opposing physiological actions?

    <p>NSAIDs and antihypertensive agents</p> Signup and view all the answers

    Which of the following drugs is least likely to cause first dose hypotension?

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

    What is a potential side effect of drug combinations involving anticoagulants?

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

    Which of the following conditions may be caused by antagonistic drug interactions?

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

    Which mechanism can cause increased serum potassium levels?

    <p>Certain antihypertensive agents causing nephrotoxicity</p> Signup and view all the answers

    What is a significant risk when patients taking insulin also use β-blockers?

    <p>Inhibition of the corrective mechanisms triggered by catecholamines</p> Signup and view all the answers

    Which herbal supplement is known to affect drug clearance through enzyme induction?

    <p>St John's Wort</p> Signup and view all the answers

    What condition can result from a significant rise in blood pressure during a hypertensive crisis?

    <p>Severe headaches and risk of intracranial haemorrhage</p> Signup and view all the answers

    Which of the following best describes the effect of Ginkgo biloba when taken with anticoagulants?

    <p>Increased risk of bleeding</p> Signup and view all the answers

    What compensatory mechanism is triggered in response to hypoglycaemia?

    <p>Release of catecholamines leading to increased blood glucose levels</p> Signup and view all the answers

    What is the primary mechanism by which enzyme inducement increases pharmacological effects?

    <p>Increased gene expression</p> Signup and view all the answers

    Which of the following is a common effect of enzyme inducers on oral contraceptives?

    <p>Decrease effectiveness</p> Signup and view all the answers

    What is a distinguishing characteristic of enzyme inhibition compared to induction?

    <p>Manifests within 2-3 days</p> Signup and view all the answers

    Which of the following is NOT a recognized mechanism of enzyme inhibition?

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

    What common pathway is most often associated with both enzyme induction and inhibition?

    <p>Phase I oxidation</p> Signup and view all the answers

    Which of the following is considered an enzyme inducer?

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

    Why might raising the dose of affected drugs due to enzyme induction be risky?

    <p>There is a risk of overdose.</p> Signup and view all the answers

    Which enzyme inhibitor can significantly increase the anticoagulant effects of drugs like warfarin?

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

    What is the effect of diuretics on sodium reabsorption?

    <p>They decrease sodium reabsorption by promoting urinary sodium excretion.</p> Signup and view all the answers

    Which drug mechanism is utilized by probenecid to affect penicillin excretion?

    <p>Competing for the same active transport systems for renal excretion.</p> Signup and view all the answers

    In an acidified tubular filtrate, how do weakly acidic drugs behave?

    <p>They are predominantly in unionized form and re-enter the blood.</p> Signup and view all the answers

    What effect does alkalized tubular filtrate have on the excretion of acidic drugs?

    <p>Increases ionization, leading to more drug excretion in urine.</p> Signup and view all the answers

    Which statement correctly describes a characteristic of P-glycoprotein in drug excretion?

    <p>It actively transports ionized drugs into the tubular lumen.</p> Signup and view all the answers

    How do thiazides and loop diuretics differ in their site of action within the nephron?

    <p>Thiazides have a more relevant effect in the proximal convoluted tubule compared to loop diuretics.</p> Signup and view all the answers

    Which mechanism is primarily responsible for drug return to the blood from tubular filtrate?

    <p>Simple passive diffusion following a concentration gradient.</p> Signup and view all the answers

    What is the small significance of urinary pH changes regarding drug metabolism?

    <p>It primarily affects the elimination of weak acids and bases in the urine.</p> Signup and view all the answers

    During drug excretion, what is the primary fate of acidic drugs in an acidified environment?

    <p>They are reabsorbed more efficiently and less is lost in urine.</p> Signup and view all the answers

    What is the consequence of competition between drugs for active transport systems in renal excretion?

    <p>Prolonged retention of one or more drugs in the renal system.</p> Signup and view all the answers

    Which of the following foods is known to decrease the effect of warfarin due to Vitamin K content?

    <p>Green leafy vegetables</p> Signup and view all the answers

    Which juice is a CYP450 inhibitor that can increase the warfarin effect?

    <p>Cranberry juice</p> Signup and view all the answers

    What is the primary mechanism by which grapefruit juice affects drug metabolism?

    <p>Inhibition of intestinal CYP3A4</p> Signup and view all the answers

    Large doses of vitamin C can inhibit the excretion of which of the following drug classes?

    <p>Pain relievers (NSAIDs)</p> Signup and view all the answers

    What effect does garlic have on drug interaction with anticoagulants?

    <p>Increases platelet activity</p> Signup and view all the answers

    Which food item is identified as an enzyme inhibitor affecting clozapine and phenytoin?

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

    The interaction with which of the following drug classes can be influenced by ginger due to thromboxane synthetase inhibition?

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

    Which of the following is a key consideration when dealing with drugs that have a narrow therapeutic window?

    <p>Monitoring serum levels</p> Signup and view all the answers

    Study Notes

    Drug Interactions Lectures 1-3

    • Drug interactions are changes in the effect of one drug due to another drug, herbal medicine, food, drink, or environmental chemicals
    • Two main types of drug interactions are pharmacokinetic and pharmacodynamic
    • Pharmacokinetic interactions affect how the body processes the drug (absorption, distribution, metabolism, excretion)
    • Pharmacodynamic interactions affect how the drug works on the body (e.g., by affecting receptor sites)
    • Drug interactions can result in a variety of outcomes, including loss of therapeutic effect, toxicity, unexpected increases in pharmacological activity, and intended or unintended beneficial effects.
    • Chemical or physical interactions, such as IV incompatibilities in fluid mixtures, can also occur.

    Types of Drug Interactions

    • Pharmacokinetic interactions are changes in drug absorption, distribution, metabolism, or excretion as a result of taking more than one drug.
      • Absorption (e.g., pH changes, altered motility)
      • Distribution (e.g., protein binding displacement)
      • Metabolism (e.g., enzyme induction/inhibition)
      • Excretion (e.g., changes in urinary pH, renal blood flow)
    • Pharmacodynamic interactions are changes in the drug's action on the body.
      • Interactions at receptor sites (e.g., competition, receptor alterations)
      • Interactions within the same physiological system (e.g., additive/synergistic, antagonistic)

    Sites of PK Interactions

    • Drug absorption: Transport of the drug within the body; influenced by factors such as absorption sites, formulation, and pH
    • Drug metabolism (biotransformation): Mostly occurs in the liver; involves enzymes like CYP3A4, CYP2D6 etc.
    • Drug displacement (protein-binding): Drugs competing for binding sites on plasma proteins, leading to changes in the amount of free drug available to act
    • Drug excretion: Removal of the drug from the body, affected by renal function and urinary pH

    Outcomes of Drug Interactions

    • Loss of therapeutic effect
    • Toxicity
    • Unexpected increases in pharmacological activity
    • Beneficial (intended) or antagonistic (unintended) effects
    • Chemical or physical interactions

    Importance of Drug Interactions

    • Adverse drug reactions (ADRs) are the 4th leading cause of death.
    • Two-thirds of ADRs are caused by drug interactions.
    • Interactions are often unpredictable.

    Drug Interactions and the Therapeutic Window

    • Therapeutic window: The range of drug concentrations that is effective without causing adverse effects.
    • Narrow therapeutic window drugs need careful monitoring to prevent toxicity.

    Absorption Interactions

    • Mechanisms: Altered pH, drug chelation, altered GI motility, induction/inhibition of drug transport proteins, drug-induced mucosal damage, altered bacterial flora
    • Changes in GI motility affect drug absorption rates.
    • Food can alter the rate of gastric emptying.
    • Induction or inhibition of drug transport proteins (e.g., P-glycoprotein) can affect oral bioavailability.
    • Separate doses of drugs to allow time for their absorption to occur
    • Activated charcoal is used for overdose, which can bind drugs and prevent their absorption.

    Distribution Interactions

    • Mechanisms: Protein binding (displacement), induction/inhibition of drug transport proteins
    • Protein-binding: Drugs compete for binding sites on plasma proteins.
    • Protein binding sites include albumin and alpha-1-acid glycoprotein.
    • Displacement can lead to increased free drug levels, which can increase the risk of overdose in some patients.

    Metabolism Interactions

    • Mechanisms: Changes in 1st-pass metabolism, enzyme activity (induction/inhibition)
    • 1st-pass metabolism: Drugs are metabolized during their first pass through the liver.
    • Enzyme induction increases the rate of metabolism, causing the drug to be eliminated more rapidly.

    Enzyme Activity

    • Environmental factors such as pH and temperature, and the concentration of substrate/enzyme can affect enzyme activity
    • Enzyme induction and inhibition
    • CYP450 enzymes (important enzymes involved in drug metabolism)
      • Induction: Increased synthesis (e.g., by St. John's Wort)
      • Inhibition: Reduced activity (e.g., by grapefruit juice)

    Excretion Interactions

    • Mechanisms: Changes in active renal tubular secretion, effects on tubular reabsorption, changes in urinary pH, changes in renal blood flow, Biliary excretion
    • Changes in urinary pH can affect the excretion of drugs.
    • Changes in renal blood flow can decrease the excretion rate of a drug.
    • Drugs that use similar renal secretion transport systems may compete for elimination.

    Drug Transporter Proteins (DTPS)

    • Drugs cross cell membranes by both passive diffusion and DTPS
    • P-glycoprotein (P-gp)
    • Location: present in intestinal walls, blood-brain barrier, and renal tubules
    • Effects: Uptake/efflux of drugs, altered bioavailability, distribution, excretion
    • Induction/inhibition: Can alter the uptake or elimination of drugs.

    Pharmacodynamic Interactions

    • Interactions at receptor sites: Competition, receptor alterations
    • Physiological interactions: Drugs affecting the same physiological systems.
    • Predictable from drug pharmacology
    • Likely to occur with related drugs

    Receptor Alteration

    • Receptor upregulation/downregulation: Chronic drug use or high plasma levels can alter the number or sensitivity of receptors, leading to changes in the drug's effect.

    Pharmacological Interaction

    • Competition for receptor sites between drugs
    • Agonists and antagonists: The effect of one drug can be enhanced or opposed by another drug.

    Physiological Interaction

    • Drugs interact with different receptors and enhance/oppose one another's action.

    Chemical Interactions

    • Two or more drugs interacting directly to alter their desired effects, and might be incompatible if mixed.

    Chemical Drug Interactions

    Additive or Synergistic Interactions

    • The combined effect of two or more drugs is greater than the sum of their individual effects.
    • Synergistic effects can be beneficial or harmful.

    Antagonistic or Opposing Interactions

    • The combined effect is less than the sum of the individual effects
    • Often the direct effect at the receptor or an opposing physiological action.
    • Direct opposition to one another

    Signal Transduction Mechanisms

    • Hypoglycemia can trigger compensatory mechanisms that involve catecholamine release.
    • Beta blockers can block the effects of catecholamines, impacting the compensatory mechanisms.

    Drug or Neurotransmitter Uptake Interactions

    • Drugs acting at adrenergic neurons
    • Receptor blocking
    • Reuptake mechanisms

    Hypertensive Crisis

    • Increased availability of noradrenaline from MAO inhibitors with indirect-acting sympathomimetics or from tricyclic antidepressants preventing noradrenaline removal.
    • Massive stimulation in blood vessels.
    • Marked rise in blood pressure.

    Drug Interactions with Food and Herbs

    • Drugs interact with food (e.g., some foods can lower/increase the amount of a drug in the body).

    Summary of Important Drugs to Watch

    • Anti-hypertensives, digoxin, theophylline, anticonvulsants, anticoagulants, cytoxics, hypoglycemics, antidepressants, and others.

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    Drug Interactions Lectures 1-3 PDF

    Description

    Test your knowledge on pharmacokinetic and pharmacodynamic drug interactions. This quiz covers various factors influencing drug absorption, risks in polypharmacy, and specific drug interactions. Challenge yourself with questions that assess your understanding of therapeutic windows and the impact of herbal supplements on drug clearance.

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