Posology definition MCQs With Answer

Introduction

Posology is the science of drug dosing—defining the right dose, route, frequency, and duration to achieve safe and effective therapy. For B. Pharm students, mastering posology means understanding the definition of posology, dose-response relationships, therapeutic index, loading and maintenance doses, and factors affecting dosage like age, weight, body surface area (BSA), renal/hepatic function, pharmacogenetics, and bioavailability. This topic links pharmacokinetics (Vd, CL, t½) and pharmacodynamics with clinical decision-making, including pediatric dosing rules (Clark’s, Young’s, BSA), dose adjustments, and therapeutic drug monitoring. This set—Posology definition MCQs With Answer—will solidify core concepts and calculations crucial for practice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the best definition of posology?

• The study of drug mechanisms at the receptor level
• The science of determining appropriate drug doses for individuals and populations
• The classification of drugs based on chemical structure
• The process of manufacturing dosage forms

Correct Answer: The science of determining appropriate drug doses for individuals and populations

Q2. The primary goal of posology is to:

• Maximize drug plasma concentration regardless of side effects
• Minimize the number of doses per day
• Balance efficacy and safety by optimizing dose and dosing regimen
• Ensure the cheapest possible therapy

Correct Answer: Balance efficacy and safety by optimizing dose and dosing regimen

Q3. Which of the following is NOT a typical factor influencing dosage in posology?

• Age and body weight
• Renal and hepatic function
• Genetic polymorphisms (pharmacogenetics)
• Color of the tablet

Correct Answer: Color of the tablet

Q4. Clark’s rule for pediatric dosing is based on:

• Body surface area
• Age in years
• Weight in pounds
• Gender and puberty status

Correct Answer: Weight in pounds

Q5. The correct formula for Clark’s rule is:

• Child dose = (Age / 12) × adult dose
• Child dose = (Weight in lb / 150) × adult dose
• Child dose = (BSA / 1.73) × adult dose
• Child dose = (Weight in kg / 70) × adult dose

Correct Answer: Child dose = (Weight in lb / 150) × adult dose

Q6. Young’s rule for pediatric dosing uses:

• Age in years
• Body surface area
• Creatinine clearance
• Lean body mass

Correct Answer: Age in years

Q7. The formula for Young’s rule is:

• Child dose = (Age / (Age + 12)) × adult dose
• Child dose = (Age / 12) × adult dose
• Child dose = (Age × Weight) / 70 × adult dose
• Child dose = (Age + 12) / Age × adult dose

Correct Answer: Child dose = (Age / (Age + 12)) × adult dose

Q8. For pediatric dosing, the most physiologically accurate method among these is:

• Clark’s rule
• Young’s rule
• Body surface area method
• Fixed fraction (half adult dose)

Correct Answer: Body surface area method

Q9. The BSA method for pediatric dosing is correctly expressed as:

• Child dose = (BSA / 1.73) × adult dose
• Child dose = (BSA × 1.73) / adult dose
• Child dose = (1.73 / BSA) × adult dose
• Child dose = (BSA × Weight) / 1.73

Correct Answer: Child dose = (BSA / 1.73) × adult dose

Q10. The correct formula for a loading dose (LD) is:

• LD = (Target concentration × Vd) / F
• LD = (Clearance × Target concentration) / F
• LD = (Vd × Clearance) / F
• LD = (F × Target concentration) / Vd

Correct Answer: LD = (Target concentration × Vd) / F

Q11. The maintenance dose rate for chronic therapy is best given by:

• MD rate = (Vd × Target concentration) / F
• MD rate = (Clearance × Target concentration) / F
• MD rate = (F × Vd) / Target concentration
• MD rate = (Half-life × Target concentration) / F

Correct Answer: MD rate = (Clearance × Target concentration) / F

Q12. Therapeutic index (TI) is usually defined as:

• ED50/TD50
• TD50/ED50
• LD50/ED50 only
• Cmax/Cmin

Correct Answer: TD50/ED50

Q13. Which statement about loading and maintenance doses is correct?

• Loading dose depends mainly on clearance
• Maintenance dose depends mainly on volume of distribution
• Loading dose depends mainly on volume of distribution and bioavailability
• Maintenance dose is independent of bioavailability

Correct Answer: Loading dose depends mainly on volume of distribution and bioavailability

Q14. Which drug property typically necessitates therapeutic drug monitoring due to narrow therapeutic index?

• Paracetamol
• Vancomycin
• Cetirizine
• Amoxicillin

Correct Answer: Vancomycin

Q15. About steady state in first-order kinetics, which is true?

• Reached after 1 half-life
• Reached after 2 half-lives
• Reached after approximately 4–5 half-lives
• Never reached with maintenance dosing

Correct Answer: Reached after approximately 4–5 half-lives

Q16. Oral drugs with extensive first-pass metabolism typically require:

• Lower oral doses than IV
• Higher oral doses than IV
• Equal oral and IV doses
• No dose adjustment

Correct Answer: Higher oral doses than IV

Q17. Bioavailability (F) is best defined as:

• The rate of drug absorption from the GI tract
• The proportion of administered dose reaching systemic circulation unchanged
• The fraction of drug bound to plasma proteins
• The distribution of drug into tissues

Correct Answer: The proportion of administered dose reaching systemic circulation unchanged

Q18. Which statement about renal impairment and dosing is MOST accurate?

• Maintenance dose rate should generally be reduced for renally cleared drugs
• Loading dose should always be reduced
• Dosing interval must always be shortened
• No change is needed if creatinine clearance is reduced

Correct Answer: Maintenance dose rate should generally be reduced for renally cleared drugs

Q19. Which drug exhibits nonlinear (saturable) kinetics making dose adjustments highly sensitive?

• Phenytoin
• Metformin
• Ceftriaxone
• Loratadine

Correct Answer: Phenytoin

Q20. Which factor increases drug accumulation at steady state for a fixed dose and interval?

• Shorter half-life
• Longer dosing interval
• Longer half-life
• Lower bioavailability

Correct Answer: Longer half-life

Q21. For aminoglycosides in obesity, dosing weight is often based on:

• Actual body weight without adjustment
• Ideal body weight (IBW) only
• Adjusted body weight (AdjBW)
• Lean body mass for all patients

Correct Answer: Adjusted body weight (AdjBW)

Q22. Which parameters are used in the Cockcroft–Gault equation for creatinine clearance?

• Age, sex, serum creatinine, and height
• Age, weight, sex, and serum creatinine
• Age, BSA, albumin, and serum creatinine
• Weight, height, and albumin

Correct Answer: Age, weight, sex, and serum creatinine

Q23. Dose–response curves on a semi-log scale are typically:

• Linear with a positive slope
• Sigmoidal (S-shaped)
• Parabolic
• Exponential with no plateau

Correct Answer: Sigmoidal (S-shaped)

Q24. If oral bioavailability (F) decreases from 1 to 0.5 and the target exposure must be maintained, the oral dose should be:

• Halved
• Doubled
• Unchanged
• Stopped

Correct Answer: Doubled

Q25. Which statement about posology in hepatic impairment is correct?

• All drugs require dose reduction
• High first-pass drugs may need reduced oral dose due to decreased clearance
• Only hydrophilic drugs are affected
• Maintenance dose is unaffected by hepatic function

Correct Answer: High first-pass drugs may need reduced oral dose due to decreased clearance

Q26. Which concept best describes the ratio of dose that produces toxicity to the dose that produces desired effect in an individual patient?

• Therapeutic index
• Therapeutic window
• Potency
• Efficacy

Correct Answer: Therapeutic window

Q27. Which is TRUE regarding dosing in neonates for renally eliminated drugs?

• Use shorter dosing intervals due to faster clearance
• Use longer dosing intervals due to immature renal function
• No change from adult dosing
• Always use adult loading and maintenance doses

Correct Answer: Use longer dosing intervals due to immature renal function

Q28. Time of administration (chronopharmacology) matters because:

• Drug potency changes randomly during the day
• Circadian rhythms can affect absorption, metabolism, and response
• Dose calculations are only valid at night
• Therapeutic index is independent of dosing time

Correct Answer: Circadian rhythms can affect absorption, metabolism, and response

Q29. Which statement correctly links pharmacokinetics to dosing?

• Increasing volume of distribution increases maintenance dose requirement
• Increasing clearance increases maintenance dose rate to maintain target concentration
• Half-life determines loading dose directly
• Bioavailability has no effect on loading dose

Correct Answer: Increasing clearance increases maintenance dose rate to maintain target concentration

Q30. For a drug with ED50 = 10 mg and TD50 = 40 mg, the therapeutic index is:

• 4
• 0.25
• 30
• 400

Correct Answer: 4

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