How is drug tolerance defined?

• A. The body becomes more sensitive, requiring smaller doses.
• B. The drug becomes ineffective regardless of dose.
• C. The body develops tolerance, requiring more of the drug to achieve the same effect.
• D. The drug's side effects disappear.

Answer: (C)

Drug tolerance happens when the body adapts to regular drug use, so the same amount produces a smaller effect and a larger dose is needed to achieve the same response. This happens because the body can change how it handles the drug (pharmacokinetic tolerance) by metabolizing it more quickly, or because the drug’s targets in the body become less responsive over time (pharmacodynamic tolerance), such as through receptor changes or altered signaling. With alcohol and other substances, tolerance can develop and often means users may escalate doses, which raises the risk of dependence and overdose. The idea that the body becomes more sensitive requiring smaller doses describes sensitization, not tolerance; the notion that the drug becomes ineffective no matter the dose isn’t accurate, since higher doses can still produce effects (albeit with greater danger); and side effects disappearing isn’t the defining feature of tolerance.