Toxicity tests: acute MCQs With Answer

Toxicity tests: acute MCQs With Answer

Introduction: Acute toxicity testing is a cornerstone of preclinical safety evaluation and an essential topic for M.Pharm students preparing for examinations and research work. This collection of focused multiple-choice questions covers principles, guidelines (OECD methods), study designs (LD50, LC50, limit and fixed dose tests), ethical considerations (3Rs, humane endpoints), statistical approaches (probit, up-and-down), and practical endpoints (clinical signs, observation period, routes). The questions emphasize conceptual understanding and practical implications for designing, interpreting, and applying acute toxicity data in drug development. Use these MCQs to strengthen your knowledge and exam readiness in biological evaluation of drug therapy.

Q1. What best defines an acute toxicity study?

• A single dose or multiple doses given within 24 hours to assess immediate toxic effects
• Repeated dosing for 28 days to assess subacute toxicity
• Chronic administration over 6 months to detect long‑term effects
• Continuous exposure for 90 days to evaluate subchronic outcomes

Correct Answer: A single dose or multiple doses given within 24 hours to assess immediate toxic effects

Q2. What does LD50 represent in toxicity testing?

• The dose that produces a therapeutic effect in 50% of subjects
• The dose that is lethal to 50% of the test population
• The dose that causes any toxic sign in 50% of animals
• The concentration in air causing death of 50% of animals

Correct Answer: The dose that is lethal to 50% of the test population

Q3. Which OECD guideline describes the Up-and-Down Procedure for acute oral toxicity?

• OECD 420
• OECD 423
• OECD 425
• OECD 408

Correct Answer: OECD 425

Q4. Which OECD guideline corresponds to the Acute Toxic Class (ATC) method?

• OECD 420
• OECD 423
• OECD 425
• OECD 414

Correct Answer: OECD 423

Q5. In many acute oral limit tests the standard limit dose commonly used is:

• 5 mg/kg
• 50 mg/kg
• 2000 mg/kg
• 10,000 mg/kg

Correct Answer: 2000 mg/kg

Q6. The primary objective of the Fixed Dose Procedure (OECD 420) is to:

• Determine the exact LD50 value to two decimal places
• Identify a dose producing clear signs of toxicity but not death
• Assess chronic toxic effects after repeated dosing
• Evaluate genetic toxicity after a single exposure

Correct Answer: Identify a dose producing clear signs of toxicity but not death

Q7. A main advantage of the Up-and-Down method over traditional LD50 tests is:

• It provides lifetime carcinogenicity data
• It uses a larger number of animals for statistical power
• It reduces the number of animals required while estimating LD50
• It eliminates the need for clinical observation

Correct Answer: It reduces the number of animals required while estimating LD50

Q8. Which route is evaluated in an acute dermal toxicity test?

• Oral gavage
• Intravenous injection
• Percutaneous (skin) exposure
• Inhalation exposure

Correct Answer: Percutaneous (skin) exposure

Q9. A validated in vitro alternative to the Draize ocular irritation test is:

• Liver microsomal assay
• BCOP (Bovine Corneal Opacity and Permeability)
• Ames bacterial reverse mutation test
• Local lymph node assay

Correct Answer: BCOP (Bovine Corneal Opacity and Permeability)

Q10. What is meant by a “humane endpoint” in acute toxicity studies?

• The time when the entire study is scheduled to end regardless of animal condition
• The earliest sign or measure that allows intervention to prevent unnecessary suffering
• A requirement to withhold analgesia to observe full toxic signs
• The point at which an animal must be excluded from statistical analysis

Correct Answer: The earliest sign or measure that allows intervention to prevent unnecessary suffering

Q11. How is the Therapeutic Index (TI) commonly calculated?

• ED50 divided by LD50
• LD50 multiplied by ED50
• LD50 divided by ED50
• LD10 divided by ED90

Correct Answer: LD50 divided by ED50

Q12. Which statistical method is commonly used to estimate LD50 from dose‑response data?

• ANOVA
• Probit analysis
• Kaplan‑Meier survival analysis
• Chi‑square test

Correct Answer: Probit analysis

Q13. According to typical acute toxicity protocols, what is the usual observation period after dosing?

• 24 hours
• 72 hours
• 14 days
• 90 days

Correct Answer: 14 days

Q14. The “3Rs” principle in animal research stands for:

• Reduce, Reuse, Recycle
• Replacement, Reduction, Refinement
• Randomization, Replication, Reproducibility
• Reduction, Restraint, Rehabilitation

Correct Answer: Replacement, Reduction, Refinement

Q15. Which of the following is a common clinical sign observed in acute systemic toxicity?

• Piloerection and lethargy
• Improved grooming and hyperactivity
• Increased body weight and appetite
• Enhanced social behavior

Correct Answer: Piloerection and lethargy

Q16. The purpose of a limit test in acute toxicity is to:

• Determine chronic toxicity endpoints over months
• Assess whether a substance produces lethal effects below a fixed high dose
• Compare two compounds for relative potency
• Evaluate genotoxic potential after a single dose

Correct Answer: Assess whether a substance produces lethal effects below a fixed high dose

Q17. In acute inhalation toxicity testing the primary metric reported is:

• LD50 (lethal dose)
• LC50 (lethal concentration)
• ED50 (effective dose)
• NOAEL (no observed adverse effect level)

Correct Answer: LC50 (lethal concentration)

Q18. The Maximum Tolerated Dose (MTD) in an acute study is defined as:

• The smallest dose that produces any measurable effect
• The highest dose that does not cause unacceptable toxicity or death
• The dose that causes 50% mortality
• The dose equivalent to human therapeutic exposure

Correct Answer: The highest dose that does not cause unacceptable toxicity or death

Q19. What is the primary purpose of including satellite animals in an acute toxicity study?

• To replace control animals during weekends
• To provide additional animals for breeding after the study
• To allow clinical pathology sampling and recovery observation without compromising main-group mortality data
• To increase the number of animals for LD50 calculation

Correct Answer: To allow clinical pathology sampling and recovery observation without compromising main-group mortality data

Q20. Under the GHS classification for acute toxicity, which category denotes the least severe acute oral toxicity?

• Category 1
• Category 2
• Category 3
• Category 5

Correct Answer: Category 5

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