GPAT–NIPER–Pharmacist Recruitment MCQs. Posology – Definition and Factors Affecting Posology

1. Which of the following BEST defines posology?

A. The study of poisons and their effects on the body

B. The branch of pharmacology dealing with drug dosages and their effects on living beings

C. The science of preparing and compounding medicines

D. The study of Prescription

Answer: B. The branch of pharmacology dealing with drug dosages and their effects on living beings

Explanation:

Posology = Study of drug doses and dosage regimens to produce the desired pharmacological effects.

Posology is the branch of pharmacology concerned with:

• Determination of appropriate drug doses

• Factors affecting dose selection

• Effects of drugs in relation to dosage in humans and animals

Conceptual Traps:

• A. Toxicology: Study of poisons and toxic effects

• C. Pharmaceutics: Preparation and compounding of medicines

• D. Prescription/Prescriptionology: Related to prescription writing, not posology

Tips:

Questions often confuse posology with:

• Toxicology

• Pharmaceutics

• Pharmacodynamics

Remember:

Posology = Dose science or drug dose quantity

2. The term "posology" is derived from Greek words that mean

A. Drug and Study
B. Poison and Logic
C. How much with science
D. Patient Therapy

Answer: C. How much + Science

Explanation:

The word Posology is derived from Greek words:

Posos = How much, Logos = Science or study

Therefore:

Posology = Science of drug dosage

Conceptual Traps:

• A. Drug + Study → More related to pharmacology

• B. Poison + Logic → Confused with toxicology

• D. Patient + Therapy → Related to therapeutics, not posology

Exam Tips (GPAT/NIPER):

Many exam questions ask:

• Origin of the term posology

• Difference between posology and dosage regimen

• Greek/Latin roots of pharmacological terms

3. Which one factor MOST significantly explains lower doses of drugs in neonates?

A. Increase in gastric emptying
B. Immature hepatic function and renal function
C. Increase in plasma proteins
D. Increase in metabolic rate

Answer: B

Explanation:

In neonates, the liver and kidneys are not fully developed, leading to:

• Reduced drug metabolism (immature hepatic enzymes)

• Reduced drug excretion (low glomerular filtration rate)

Neonates: Slow hepatic metabolism + slow renal excretion. Increased drug accumulation

This increases the risk of:

• Drug accumulation

• Toxicity

• Prolonged drug action

Hence, lower doses or increased dosing intervals are often required.

Conceptual Traps:

• A. Increase in gastric emptying: Neonates actually have slower/irregular gastric emptying

• C. Increase in plasma proteins: Neonates have lower plasma protein levels

• D. Increase in metabolic rate: Not the major reason for dose reduction

GPAT/NIPER Pearl:

Classic examples of neonatal toxicity due to immature metabolism:

• Chloramphenicol: Gray baby syndrome

• Sulfonamides: Kernicterus

4. Why do geriatric patients require low drug doses?

A. Very slow Drug absorption
B. Decrease in Hepatic and renal clearance with age
C. Low Gastric pH
D. Slow peristaltic movement

Answer: B Decrease in hepatic and renal clearance with age

Explanation:

In geriatric patients, aging causes:

• Reduced liver metabolism

• Reduced kidney function (Decreased GFR and renal clearance)

Aging decreased hepatic clearance, decreased renal clearance + increased drug half-life and toxicity

As a result:

• Drugs remain longer in the body

• Risk of adverse effects and toxicity increases

• Lower doses are often required

Conceptual Traps:

• A. Very slow drug absorption: Absorption usually changes minimally with age

• C. Low gastric pH: The elderly often have increased gastric pH (less acid)

• D. Slow peristaltic movement: May occur, but not the main reason for dose reduction

GPAT/NIPER Tips:

Common high-risk drugs in geriatrics:

• Benzodiazepines

• Digoxin

• Aminoglycosides

• NSAIDs

Rule:

“Start low and go slow” in elderly patients.

5. Which dosage calculation is based on body weight?

A. Fried’s formula
B. Clark’s formula
C. Young’s formula
D. Dilling’s formula

Answer: B Clark’s formula

Explanation:

• Clark’s formula calculates pediatric dose based on body weight (in pounds):

Child dose = Weight (lb)/150 X adult dose.

Other options:

• A. Fried’s formula: based on age (infants)

• C. Young’s formula: based on age

• D. Dilling’s formula: based on age

So, only Clark’s formula is weight-based.

7. Which one calculates pediatric dose depending on age?

A. Posological index
B. Surface area formula only
C. Young’s formula
D. Clark’s formula

Answer: C

The correct answer is:

C. Young’s formula

Explanation:

• Young’s formula calculates pediatric dose based on age:

Child dose = Age (years)/Age + 12 X Adult dose

Why others are incorrect:

• A. Posological index: not a standard age-based dosing formula (general term)

• B. Surface area formula only: based on body surface area (BSA), not age directly

• D. Clark’s formula: based on body weight

So, the age-based pediatric dosing formula among the options is Young’s formula.

8. A 4-year-old child requires a dose calculated by Young’s formula. If the adult dose is 250 mg, the child's dose will be

Child dose = Age/Age + 12 X Adult dose}

A. 55 mg
B. 60 mg
C. 63 mg
D. 100 mg

Answer: C

Calculation:
4/(4+12) × 250 = 62.5 mg

9. Select the factor that affects the dose of the drug because IV administration provides 100% bioavailability.

A. Age
B. Sex
C. Route of administration
D. Weight

Answer: C

IV administration gives 100% bioavailability because the drug directly enters systemic circulation. Therefore, the factor affecting the dose here is the C. Route of administration

Different routes (oral, IV, IM, etc.) change the amount of drug reaching the bloodstream, so dose adjustments may be needed.

10. Which phenomenon occurs after repeated administration of drug in short intervals, causing rapid loss of effect?

A. Tolerance
B. Synergism
C. Tachyphylaxis
D. Antagonism

Answer: C

Explanation:
Tachyphylaxis is a sudden decrease in drug effect occurring within a short time due to repeated dosing.

• Tolerance develops gradually over a longer period.

• Synergism means enhanced effect when two drugs are combined.

• Antagonism means one drug opposes the action of another.

11. Tachyphylaxis is commonly associated with:

A. Ampicillin
B. Ephedrine
C. Digitoxin
D. Warfarin

Answer: B

Ephedrine commonly shows tachyphylaxis because repeated use rapidly depletes stored norepinephrine from nerve endings.

• Ampicillin is not typically associated with tachyphylaxis

• Digitoxin is associated more with toxicity concerns

• Warfarin requires dose monitoring, not tachyphylaxis

12. Which factor that affects posology is MOST accurately matched?

A. Synergism: one drug opposes another
B. Antagonism: enhanced combined action
C. Idiosyncrasy: abnormal genetically determined response
D. Tolerance: immediate allergic response

Answer: C

Explanation:

• Idiosyncrasy = unusual or genetically determined abnormal response to a drug

• Synergism means enhanced combined action, not opposition

• "Antagonism" means drug opposition, not enhancement

• Tolerance is a reduced response over time, not an immediate allergy

13. The combined therapeutic action of two drugs exceeds the sum of individual effects is

A. Antagonism
B. Potentiation/Synergism
C. Tachyphylaxis
D. Idiosyncrasy

Answer: B

Synergism occurs when two drugs work together to produce a stronger therapeutic effect.

• Antagonism: opposite effect

• Tachyphylaxis: rapid decrease in response

• Idiosyncrasy: unusual response due to genetic factors

14. Which one condition REQUIRES dose reduction due to impaired drug excretion?

A. Hyperthyroidism
B. Renal failure
C. Hypertension
D. Migraine

Answer: B

Renal failure reduces the excretion of many drugs, causing drug accumulation and possible toxicity. Therefore, dose reduction is often required.

• Hyperthyroidism — may alter metabolism but not mainly excretion

• Hypertension — does not directly require dose reduction for excretion problems

• Migraine — unrelated to impaired drug excretion

15. Which factor is MOST useful to calculate dose accurately in obese or lean patients?

A. Age
B. Gender
C. Body surface area
D. Emotional status

Answer: C

Body surface area is considered the most accurate method for dose calculation in obese or lean patients because it correlates better with metabolic activity, blood volume, and organ function.

• Age alone may not reflect body composition

• Gender is less accurate for dose calculation

• Emotional status does not determine drug dose directly

16. Which one is the average adult body surface area (BSA) considered for dose calculation?

A. 0.70 m²
B. 1.0 m²
C. 1.73 m²
D. 2.70 m²

Answer: C

The body surface area of an average adult is generally considered to be 1.73 m², and it is commonly used as the standard reference in dose calculations and renal function assessment.

17. Drug accumulation occurs when:

A. Elimination exceeds absorption
B. Drug metabolism is absent
C. Absorption rate exceeds elimination rate
D. Drug is administered orally only

Answer: C

Drug accumulation occurs when the body cannot eliminate the drug as quickly as it is absorbed or administered, leading to increased drug concentration and possible toxicity.

• If elimination exceeds absorption, accumulation will not occur

• Metabolism may be reduced, but not necessarily absent

• Drug accumulation can occur with any route of administration, not only oral drugs

18. Which one is an example of tolerance?

A. Reduced response to repeated nicotine use
B. Penicillin allergy
C. Morphine-induced rash
D. Aspirin-induced bleeding

Answer: A

Tolerance develops when repeated exposure to a drug causes decreased effectiveness, so larger doses may be needed to produce the same effect.

• Penicillin allergy is a hypersensitivity reaction

• Morphine-induced rash is an adverse effect

• Aspirin-induced bleeding is a side effect/adverse reaction

19. "Idiosyncrasy" is

A. Expected pharmacological action
B. Abnormal, unusual response to a drug
C. Drug antagonism
D. Psychological dependence

Answer: B

Idiosyncrasy refers to an unusual and unexpected reaction to a drug, often due to genetic differences in an individual.

• Expected pharmacological action = normal drug effect

• Drug antagonism = one drug opposes another

• Psychological dependence = emotional reliance on a drug

20. Which factor affecting posology is MOST related to the placebo effect?

A. Environmental factor
B. Emotional factor
C. Body weight
D. Route of administration

Answer: B

The placebo effect mainly depends on the patient's beliefs, expectations, emotions, and psychological state. Therefore, it is most closely related to the emotional factor affecting drug response.

21. Which one for pediatric posology is CORRECT?

A. Children need higher doses than adults
B. Pediatric doses do not depend upon body weight
C. Immature blood-brain barrier (BBB) and enzyme activities alter drug responses.
D. Rapid Renal excretion in neonates

Answer: C

In pediatric patients, especially neonates and infants, the BBB and liver enzyme systems are not fully developed, which can significantly change drug action and toxicity.

Why others are incorrect:

• A. Children usually require lower or carefully adjusted doses, not higher than adults.

• B. Pediatric doses often depend on body weight or body surface area.

• D. Neonates generally have slow renal excretion due to immature kidney function, not rapid excretion.

22. MATCH the pair CORRECTLY.

A. Antagonism: enhanced action
B. Synergism: opposing action
C. Tachyphylaxis: rapid tolerance
D. Idiosyncrasy: cumulative toxicity

Answer: C

Explanation:

• Tachyphylaxis refers to a rapid decrease in response to a drug after repeated administration over a short period.

Why others are incorrect:

• A. Antagonism = opposing action, not enhanced action.

• B. Synergism = enhanced/combined action, not opposing action.

• D. Idiosyncrasy = unusual abnormal response to a drug, not cumulative toxicity.

23. Choose the correct definition of "dose" in pharmacology:

A. Drug quantity to produce a toxic effect only
B. Drug quantity to produce the desired therapeutic effect
C. Drug quantity administered at once
D. Drug quantity to control disease.

Answer: B

Dose is defined as the amount of a drug required to produce the intended or desired therapeutic effect in the body.

24. Which factor may change the sedatives' effectiveness between day and night?

A. Body weight
B. Environment
C. Sex
D. Synergism

Answer: B

Environmental factors such as day-night cycle, light, noise, sleep pattern, and surroundings can influence the effectiveness of sedatives. Sedatives often show different effects during daytime and nighttime due to changes in physiological and environmental conditions.

25. A patient requiring a higher dose develops due to a reduced response after prolonged use of morphine. This is

A. Potentiation
B. Idiosyncrasy
C. Tolerance
D. Tachyphylaxis

Answer: C

Tolerance develops when repeated or prolonged use of a drug like morphine causes a reduced response, so progressively higher doses are needed to produce the same effect.

• Tachyphylaxis = rapid tolerance occurring in a short time.

• Potentiation = enhancement of drug effect.

• Idiosyncrasy = abnormal, unusual response.

26. Which route requires the LOWEST dose?

A. Intravenous
B. Intramuscular
C. Subcutaneous
D. Sublingual

Answer: A

The intravenous (IV) route requires the lowest dose because the drug is delivered directly into the bloodstream with 100% bioavailability and no first-pass metabolism.

27. The therapeutic effect of one drug reduced by another is:

A. Synergism
B. Potentiation
C. Antagonism
D. Accumulation

Answer: C

Antagonism occurs when one drug reduces or blocks the therapeutic effect of another drug.

28. Which one of the following is NOT a factor that affects posology?

A. Sex
B. Age
C. Body weight
D. Tablet color

Answer: D

29. Under which condition do women require a dose adjustment?

A. Menstruation
B. Pregnancy
C. Lactation
D. All of the above

Answer: D

Women may require dose adjustment during the following:

• Menstruation – hormonal changes can affect drug response.

• Pregnancy – physiological changes alter drug absorption, distribution, metabolism, and excretion.

• Lactation – drugs may pass into breast milk and affect the infant.

30. Rapid decrease in drug response after repeated administration of ephedrine is due to

A. Drug antagonism
B. Tachyphylaxis
C. Hypersensitivity
D. Drug accumulation

Answer: B

Tachyphylaxis is a rapid decrease in response to a drug after repeated administration in a short period. Ephedrine is a classic example.

High-Yield GPAT/NIPER: Pharmacist exams Revision Points

• Posology = Science of dosage

• Major factors: Age, weight, BSA, sex, disease, route, tolerance, tachyphylaxis

• Neonates & geriatrics usually require lower doses

• IV route → highest bioavailability

• Tachyphylaxis = rapid tolerance

• Synergism > additive effect

• Antagonism = opposing effect

  Dr Alok Singh