Inter-individual variability in drug response refers to differences in drug response between which groups?

• A. The same individual over time
• B. Between different tissues within the same individual
• C. Between different individuals
• D. Across different species

Answer: (C)

The main idea is that people can respond differently to the same drug because of inherent differences between individuals. Inter-individual variability refers to how the drug’s effect can vary from one person to another, due to factors like genetics (enzyme variants), age, sex, organ function, disease states, other medications, and lifestyle. These factors can alter both pharmacokinetics (how the body handles the drug) and pharmacodynamics (how the drug affects the body), leading to different dose-response outcomes across people. Intra-individual variability would be changes in the same person over time, differences between tissues within one person reflect tissue-specific effects, and differences across species pertain to interspecies variability.