Tachyphylaxis MCQs With Answer

Tachyphylaxis MCQs With Answer

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Introduction

Tachyphylaxis MCQs With Answer is a concise, high-yield review designed for B.Pharm students studying pharmacology and drug tolerance. This set focuses on tachyphylaxis — the rapid loss of drug effect after repeated dosing — covering mechanisms such as receptor desensitization, internalization, second messenger depletion, and clinical implications for drugs like nitrates, topical decongestants and β2-agonists. Questions emphasize differentiation between tachyphylaxis and tolerance, experimental measurement, management strategies (drug holidays, dose adjustment, switching classes) and molecular pathways (GRKs, arrestins). Ideal for exam prep and concept mastery, these MCQs reinforce understanding of pharmacodynamics, therapeutic planning and patient safety. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the best definition of tachyphylaxis?

  • A rapid decrease in drug effect after repeated administration over a short period
  • A gradual reduction in response due to metabolic enzyme induction over weeks
  • An allergic reaction following first exposure to a drug
  • An increase in drug effect after dose escalation

Correct Answer: A rapid decrease in drug effect after repeated administration over a short period

Q2. Which mechanism most commonly explains tachyphylaxis at the receptor level?

  • Receptor internalization and sequestration
  • Hepatic enzyme induction
  • Increased renal excretion
  • Formation of drug antibodies

Correct Answer: Receptor internalization and sequestration

Q3. How does tachyphylaxis differ from pharmacokinetic tolerance?

  • Tachyphylaxis is usually rapid and pharmacodynamic; pharmacokinetic tolerance involves metabolic changes over time
  • Tachyphylaxis always involves immune mechanisms; pharmacokinetic tolerance does not
  • Tachyphylaxis increases drug plasma levels; pharmacokinetic tolerance decreases plasma levels
  • They are identical; both terms are interchangeable

Correct Answer: Tachyphylaxis is usually rapid and pharmacodynamic; pharmacokinetic tolerance involves metabolic changes over time

Q4. Which clinical example is classically associated with tachyphylaxis?

  • Topical nasal decongestants like oxymetazoline
  • Long-term beta-blocker therapy for hypertension
  • Chronic warfarin anticoagulation
  • Steady dosing of levothyroxine

Correct Answer: Topical nasal decongestants like oxymetazoline

Q5. Which intracellular event can lead to tachyphylaxis of G-protein coupled receptor (GPCR) agonists?

  • Phosphorylation of the receptor by GRKs and binding of arrestin
  • Increased mRNA transcription for the receptor
  • Activation of mitochondrial biogenesis
  • Direct DNA alkylation

Correct Answer: Phosphorylation of the receptor by GRKs and binding of arrestin

Q6. A decrease in which pharmacodynamic parameter is commonly seen with tachyphylaxis?

  • Maximal effect (Emax)
  • Drug half-life
  • Volume of distribution
  • Plasma protein binding

Correct Answer: Maximal effect (Emax)

Q7. Which drug class used in asthma can show tachyphylaxis with frequent use?

  • Short-acting β2-agonists (e.g., salbutamol)
  • Inhaled corticosteroids
  • Leukotriene receptor antagonists
  • Long-acting muscarinic antagonists

Correct Answer: Short-acting β2-agonists (e.g., salbutamol)

Q8. Which experimental observation would most strongly indicate tachyphylaxis rather than pharmacokinetic change?

  • Unchanged plasma drug concentration with reduced pharmacologic effect
  • Decreased plasma drug concentration with reduced effect
  • Increased urinary excretion of unchanged drug
  • Elevation of liver enzymes after chronic dosing

Correct Answer: Unchanged plasma drug concentration with reduced pharmacologic effect

Q9. Which management strategy is frequently recommended to reverse or prevent tachyphylaxis?

  • Drug-free interval or “drug holiday”
  • Immediate doubling of dose indefinitely
  • Combining with a nephrotoxic agent
  • Abrupt cessation without monitoring

Correct Answer: Drug-free interval or “drug holiday”

Q10. Tachyphylaxis caused by depletion of intracellular mediators is best described as which type of mechanism?

  • Second messenger depletion
  • Transcriptional downregulation
  • Autoimmune neutralization
  • Enhanced biliary excretion

Correct Answer: Second messenger depletion

Q11. Which of the following drugs is known for rapid tachyphylaxis when used topically for rhinitis?

  • Phenylephrine nasal spray
  • Oral loratadine
  • Topical mupirocin
  • Intranasal cromolyn

Correct Answer: Phenylephrine nasal spray

Q12. Receptor downregulation leading to decreased receptor number primarily involves which cellular process?

  • Accelerated receptor degradation after internalization
  • Increased ribosomal protein synthesis
  • Enhanced receptor glycosylation on the cell surface
  • Activation of cytochrome P450 enzymes

Correct Answer: Accelerated receptor degradation after internalization

Q13. Which laboratory technique can demonstrate receptor internalization contributing to tachyphylaxis?

  • Immunofluorescence microscopy of receptor localization
  • Serum creatinine measurement
  • Urine drug screen for metabolites
  • Complete blood count

Correct Answer: Immunofluorescence microscopy of receptor localization

Q14. If tachyphylaxis reduces Emax without changing EC50, what does this suggest about the drug-receptor interaction?

  • Noncompetitive mechanism reducing efficacy
  • Competitive antagonism at the receptor
  • Purely pharmacokinetic elimination
  • Enhanced receptor affinity

Correct Answer: Noncompetitive mechanism reducing efficacy

Q15. Which of the following is least likely to cause tachyphylaxis?

  • Once-weekly dosing of a stable receptor agonist
  • Continuous topical application of an α-agonist
  • Repeated high-frequency dosing of a β-agonist
  • Rapid, repeated administration of epinephrine-like drugs

Correct Answer: Once-weekly dosing of a stable receptor agonist

Q16. In clinical practice, how is nitrate tolerance (tachyphylaxis) commonly managed?

  • Providing a nighttime nitrate-free interval
  • Increasing oral nitrate dose continuously
  • Combining nitrates with nitrates from another source
  • Stopping aspirin therapy

Correct Answer: Providing a nighttime nitrate-free interval

Q17. Which molecular adaptor is directly involved in uncoupling GPCRs during tachyphylaxis?

  • Arrestin
  • NF-κB
  • Tubulin
  • Heat-shock protein 70

Correct Answer: Arrestin

Q18. A patient using topical decongestant for 10 days complains of worsening congestion. This clinical picture most likely represents:

  • Tachyphylaxis (rebound congestion)
  • Immediate hypersensitivity
  • Systemic toxicity from overuse
  • Primary disease progression only

Correct Answer: Tachyphylaxis (rebound congestion)

Q19. Which pharmacological measurement curve shift is characteristic of a decrease in potency (increase in EC50) without change in Emax?

  • Rightward parallel shift of dose-response curve
  • Downward lowering of maximal response only
  • Leftward shift indicating increased potency
  • No change in curve despite clinical unresponsiveness

Correct Answer: Rightward parallel shift of dose-response curve

Q20. Which strategy can minimize tachyphylaxis to β2-agonists in asthma management?

  • Using inhaled corticosteroids to reduce receptor desensitization
  • Increasing frequency of short-acting β2-agonist doses daily
  • Stopping all controller medications abruptly
  • Using systemic antibiotics prophylactically

Correct Answer: Using inhaled corticosteroids to reduce receptor desensitization

Q21. Tachyphylaxis due to second messenger depletion is most likely when the drug acts through which pathway?

  • Signaling that exhausts intracellular mediators (e.g., nitric oxide or cGMP pathways)
  • Direct DNA intercalation
  • Enzyme replacement therapy
  • Passive diffusion into adipose tissue

Correct Answer: Signaling that exhausts intracellular mediators (e.g., nitric oxide or cGMP pathways)

Q22. Which experimental change would indicate receptor downregulation as the cause of tachyphylaxis?

  • Reduced receptor density on cell surface measured by radioligand binding
  • Increased drug clearance by liver enzymes
  • Rise in plasma protein binding
  • Enhanced renal tubular reabsorption

Correct Answer: Reduced receptor density on cell surface measured by radioligand binding

Q23. Which phrase correctly describes tachyphylaxis onset?

  • Rapid onset over minutes to days after repeated dosing
  • Slow onset over months due to genetic adaptation
  • Immediate on first exposure only
  • Only occurs after drug accumulation in fat

Correct Answer: Rapid onset over minutes to days after repeated dosing

Q24. Combining an agonist with which of the following is least likely to prevent tachyphylaxis?

  • An antagonist of the same receptor given continuously
  • A drug that restores second messenger levels
  • An agent that reduces receptor phosphorylation
  • A dosing schedule that includes drug-free intervals

Correct Answer: An antagonist of the same receptor given continuously

Q25. Which observation during dose–response studies suggests a noncompetitive mechanism underlying tachyphylaxis?

  • Decrease in maximal effect regardless of agonist concentration
  • Reserve of effect recovered by increasing agonist concentration
  • No change in Emax but increased slope of curve
  • Complete restoration of response after adding more agonist

Correct Answer: Decrease in maximal effect regardless of agonist concentration

Q26. In preclinical models, which intervention can demonstrate reversibility of tachyphylaxis?

  • Allowing a washout period and re-challenging with the agonist
  • Continuous infusion of the agonist for a longer time
  • Co-administering an enzyme inducer
  • Measuring hepatic enzyme levels only

Correct Answer: Allowing a washout period and re-challenging with the agonist

Q27. Which wording best reflects the clinical implication of tachyphylaxis for prescribers?

  • Monitor response closely and adjust regimen using holidays or alternative agents
  • Assume efficacy will remain constant and never adjust therapy
  • Always double the dose at the first sign of reduced response
  • Discontinue all other medications immediately

Correct Answer: Monitor response closely and adjust regimen using holidays or alternative agents

Q28. Tachyphylaxis involving immune-mediated neutralization of a biologic would be classified as which mechanism?

  • Antibody-mediated pharmacodynamic change
  • Hepatic enzyme induction
  • Second messenger depletion
  • Membrane lipid peroxidation

Correct Answer: Antibody-mediated pharmacodynamic change

Q29. Which measurement distinguishes tachyphylaxis from simple disease progression?

  • Stable drug concentration with falling pharmacologic effect suggests tachyphylaxis
  • Progressive worsening of symptoms always indicates tachyphylaxis
  • Improved effect despite same dosing indicates tachyphylaxis
  • Any adverse reaction reflects tachyphylaxis

Correct Answer: Stable drug concentration with falling pharmacologic effect suggests tachyphylaxis

Q30. For exam preparation, which study focus will best deepen understanding of tachyphylaxis for B.Pharm students?

  • Mechanisms of receptor desensitization, clinical examples, and management strategies
  • Only drug pricing and pharmacy law
  • Basic sterile compounding techniques exclusively
  • Nutrition counseling unrelated to pharmacology

Correct Answer: Mechanisms of receptor desensitization, clinical examples, and management strategies

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