What is the distinction between resistance and tolerance in drug response?

The distinction between tolerance and resistance lies in the specific contexts in which these terms are used and their implications for drug response.

Tolerance refers to a condition that develops in individuals as a result of continued exposure to a drug. Over time, a person's body may become accustomed to the drug, leading to a diminished pharmacological effect. This means that higher doses may be needed to achieve the same therapeutic effect initially experienced. This phenomenon is particularly relevant in pharmacology when discussing how individuals may react differently to medication over time as their bodies adapt.

On the other hand, resistance typically refers to the diminished efficacy of a drug in targeting a specific pathogen, such as bacteria or cancer cells. For example, certain cancer cells may become resistant to chemotherapy drugs, meaning that the drugs that once effectively targeted and killed these cells are no longer effective. In this context, resistance involves microorganisms or cancer cells that evolve or acquire mechanisms to evade the effects of drugs.

This understanding clarifies why the correct answer emphasizes the relationship between tolerance in individuals and resistance in cancer cells, highlighting the specific mechanisms at play in each scenario.