Which of the following observations is undertaken in repeat-dose but not single-dose toxicity studies?

Question

BlackTom AI · Accepted Answer

Question restatement: The task asks which observation is undertaken in repeat-dose toxicity studies but not in single-dose toxicity studies.

Option 1: Mortality
- Mortality is a fundamental endpoint in both single-dose and repeat-dose toxicity studies. It reflects acute and cumulative toxicity, and data from a single high dose can yield mortality, while repeat-dose studies also monitor mortality over time. Therefore, this option is incorrect as an exclusive repeat-dose observation.

Option 2: Body weight
- Body weight change is commonly tracked in both study designs. In a single-dose study, body weight may be monitored to assess acute effects, and in repeat-dose studies it is tracked regularly to identify progressive or cumulative toxicity. Thus, this is not exclusive to repeat-dose studies.

Option 3: Clinical chemistry
- Clinical chemistry (blood/serum biomarkers such as liver enzymes, kidney function markers, etc.) is routinely measured in repeat-dose toxicity studies to detect organ-specific toxicities and subclinical effects that may not be evident from gross observations or mortality alone. In many protocols, clinical chemistry is either not collected or limited in single-dose studies, making this observation more characteristic of repeat-dose investigations. This aligns with the idea that cumulative exposure reveals biochemical changes requiring monitoring.

Option 4: Necropsy
- Necropsy (gross pathological examination) is typically performed in toxicity studies to identify organ-level effects after the study ends. It can be conducted in both single-dose and repeat-dose studies, depending on design and regulatory requirements. Therefore, it is not exclusive to repeat-dose studies.

Summary of reasoning: Among the options, mortality and body weight can be observed in both single-dose and repeat-dose studies, and necropsy is commonly performed in both contexts as well. Clinical chemistry, however, is more specifically associated with repeat-dose toxicity studies where repeated exposure can reveal biochemical changes over time that are not assessed in a single-dose design. This makes Clinical chemistry the observation undertaken in repeat-dose but not in single-dose toxicity studies.

PCOL2021 2025 Practice MCQ Section A - 2025

Which of the following observations is undertaken in repeat-dose but not single-dose toxicity studies?

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