Examples of genetic factors as a source of variability in drug response?

• A. Change in number/function of receptors and metabolism
• B. Diet alone
• C. Sleep patterns
• D. Hair color

Answer: (A)

Genetic differences in how drugs work and are processed create variability in responses. If someone has fewer receptors or receptors with altered function, a given dose may produce a weaker effect or different signaling. Conversely, more receptors or receptors with higher affinity can enhance responsiveness. Similarly, genetic polymorphisms in drug-metabolizing enzymes, like members of the cytochrome P450 family, can make a person a poor, intermediate, extensive, or ultrarapid metabolizer. This changes both the concentration of the drug in the body and how long it stays there, affecting efficacy and risk of toxicity. These genetic factors directly shape pharmacodynamics (receptor target) and pharmacokinetics (metabolism), leading to meaningful variability in drug response.

Diet, sleep patterns, and hair color aren’t genetic factors that determine drug response in the same direct way. Diet and sleep can influence drug effects through non-genetic mechanisms or physiology, and hair color is a phenotypic trait not typically involved in how a drug is targeted or metabolized.