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. (A)</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 (A)</p> Signup and view all the answers

Which drug interaction is characterized by opposing physiological actions?

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

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

<p>Furosemide (A)</p> Signup and view all the answers

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

<p>Thromboembolism (B)</p> Signup and view all the answers

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

<p>Hypotension (C)</p> Signup and view all the answers

Which mechanism can cause increased serum potassium levels?

<p>Certain antihypertensive agents causing nephrotoxicity (B)</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 (C)</p> Signup and view all the answers

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

<p>St John's Wort (D)</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 (D)</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 (C)</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 (D)</p> Signup and view all the answers

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

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

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

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

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

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

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

<p>Allosteric (D)</p> Signup and view all the answers

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

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

Which of the following is considered an enzyme inducer?

<p>Rifampicin (A)</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. (D)</p> Signup and view all the answers

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

<p>Ketoconazole (C)</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. (A)</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. (B)</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. (D)</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. (C)</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. (D)</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. (C)</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. (D)</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. (B)</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. (C)</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. (C)</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 (B)</p> Signup and view all the answers

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

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

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

<p>Inhibition of intestinal CYP3A4 (C)</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) (D)</p> Signup and view all the answers

What effect does garlic have on drug interaction with anticoagulants?

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

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

<p>Soya (D)</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 (A)</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 (C)</p> Signup and view all the answers

Flashcards

Pharmacokinetic Interactions

Changes in the concentration of a drug in the bloodstream due to interactions with other drugs.

Absorption Interactions

A drug interaction that affects how a drug is absorbed from the gut into the bloodstream.

Drug Metabolism

The process by which drugs are broken down in the body, primarily by enzymes in the liver.

Drug Displacement (Protein-Binding)

A drug interaction that occurs when two drugs compete for the same binding site on a protein in the blood, reducing the amount of one drug that is available to reach its target.

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Drug Excretion

The process by which drugs and their metabolites are eliminated from the body, mainly through the kidneys.

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Enzyme Induction

A process that increases the activity of enzymes in the body, primarily in the liver, by increasing the amount of enzyme produced.

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Enzyme Inducer

A substance that triggers enzyme induction, increasing the rate of enzyme production.

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Enzyme Inhibition

A process that decreases the activity of enzymes, slowing down or stopping their function.

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Enzyme Inhibitor

A substance that causes enzyme inhibition, reducing the activity of enzymes.

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Phase I oxidation

The most common pathway for drug metabolism, involving enzymes like cytochrome P450 (CYP450).

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Drug-Enzyme Interaction

A common interaction between drugs, insecticides, and even smoking tobacco, where one substance alters the activity of enzymes involved in drug metabolism.

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Time to Develop Enzyme Induction

The time it takes for enzyme induction to develop and become fully effective, typically 2-3 weeks.

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Time to Develop Enzyme Inhibition

The time it takes for enzyme inhibition to become evident, usually 2-3 days.

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Antagonistic Interactions

Interactions where drugs have opposing effects, leading to a reduction in their intended effect.

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Drug Displacement

Interactions that occur when two drugs compete for the same binding site on a protein in the blood, decreasing the concentration of one or both drugs.

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Signal Transduction Interference

A type of antagonistic interaction where one drug reduces the effectiveness of another drug by blocking its signaling pathway.

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NSAIDs and Antihypertensive Agents

Interactions that occur when a drug inhibits the synthesis of prostaglandins, which can lead to increased vascular tone and diminished effect of antihypertensive medications.

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Renal Excretion

The movement of drugs from the blood into the urine.

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Active Transport Competition

A type of drug interaction that occurs when two drugs compete for the same active transport system in the kidneys.

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P-glycoprotein

A protein that pumps certain drugs out of cells, including those in the kidneys and liver.

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Ion Trapping

A process used by some drugs to be excreted in urine, where the drug is eliminated in its ionized form.

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Urinary pH Changes

A change in the pH of the urine can affect the reabsorption of drugs, particularly weak acids and bases.

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Hypoglycemia

A condition where blood sugar levels are too low, often causing symptoms like sweating, dizziness, and confusion. It's usually caused by too much insulin or insufficient food intake.

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Catecholamines

Hormones like adrenaline and noradrenaline released from the adrenal glands in response to low blood sugar. They help raise blood sugar levels by stimulating the liver to release glucose.

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Hypertensive Crisis

A condition where blood pressure is extremely high, often resulting in severe headaches, intracranial bleeding, and even death.

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Beta-blockers

Drugs that block the effects of beta-adrenergic receptors, which are involved in the body's response to stress and low blood sugar. They can mask symptoms of hypoglycemia by preventing the release of catecholamines.

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How do green leafy vegetables affect warfarin?

Green leafy vegetables, like spinach and kale, reduce the effectiveness of warfarin by providing an alternative source of vitamin K, which is essential for blood clotting. Since warfarin works by inhibiting vitamin K, increased vitamin K intake decreases warfarin's effect.

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What effect do cruciferous veggies have on warfarin?

Cruciferous vegetables, including sprouts, cabbage, and broccoli, induce (increase the activity of) enzymes in the liver, particularly CYP450, which breaks down warfarin, decreasing its effectiveness.

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How do char-grilled meats and avocados affect warfarin?

Char-grilled meats and avocados can induce (increase the activity of) CYP450 enzymes, leading to a faster breakdown of warfarin, resulting in a reduced effect.

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How do cranberry juice, grapefruit juice, and soya affect warfarin?

Cranberry juice, grapefruit juice, and soya inhibit (decrease the activity of) CYP450 enzymes, causing warfarin to break down slower, leading to higher blood levels and potentially increased anticoagulant effect.

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How does grapefruit juice affect medication?

Grapefruit juice inhibits CYP3A4, an enzyme in the intestine, leading to reduced breakdown of some medications, like certain calcium channel blockers, cyclosporine, and terfenadine, resulting in higher drug levels and potentially increased effects.

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How does vitamin C affect certain medications?

Large doses of vitamin C acidify urine, preventing the excretion of certain medications like NSAIDs, acetaminophen, and tetracyclines, leading to increased blood levels and potential side effects.

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How does soya affect medication?

Soya contains compounds that can inhibit certain enzymes, leading to increased blood levels and potential side effects of medications like clozapine, haloperidol, NSAIDs, and phenytoin, which are broken down by these enzymes.

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How does garlic interact with anticoagulants and NSAIDs?

Garlic increases platelet activity, potentially increasing the risk of bleeding when combined with anticoagulants or NSAIDs, which also increase bleeding risk.

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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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