Which statement best describes intra-individual variability in drug response?

Which statement best describes intra-individual variability in drug response?

• A. Differences in drug response in the same individual.
• B. Differences in drug response between different individuals.
• C. Differences in drug response across species.
• D. Differences in drug response due to manufacturing differences.

Answer: (A)

Intra-individual variability refers to differences in a drug’s effect within the same person, across time or repeated administrations, due to factors like physiological changes, enzyme activity, organ function, adherence, or interactions that can vary for that individual. That’s why the statement describing differences in drug response in the same individual is the best fit. The other ideas describe different kinds of variability: differences between different people (inter-individual), differences across species (interspecies), or differences arising from manufacturing factors (extrinsic product variability), none of which capture the within-person fluctuations at the heart of intra-individual variability.

Intra-individual variability refers to differences in a drug’s effect within the same person, across time or repeated administrations, due to factors like physiological changes, enzyme activity, organ function, adherence, or interactions that can vary for that individual.

That’s why the statement describing differences in drug response in the same individual is the best fit. The other ideas describe different kinds of variability: differences between different people (inter-individual), differences across species (interspecies), or differences arising from manufacturing factors (extrinsic product variability), none of which capture the within-person fluctuations at the heart of intra-individual variability.