Which term describes needing more of a substance to achieve the same effect?

• A. Intoxication
• B. Withdrawal
• C. Tolerance
• D. Dependence

Answer: (C)

Tolerance is the body's adaptation to repeated substance exposure, leading to a diminished effect at the same dose and the need for larger amounts to achieve the same result. This happens because the body can change how it responds to the drug—receptors may become less responsive (pharmacodynamic tolerance) or the body may become more efficient at metabolizing the drug (metabolic tolerance). As a result, someone using regularly may escalate their dose to chase the same level of effect. It’s important to distinguish this from intoxication, which is the current state of impairment from the drug, and from withdrawal, which are the symptoms that occur when the drug is not used. It’s also related to dependence in that tolerance can be part of a dependent pattern, but tolerance itself simply describes needing more of the substance to achieve the same effect. Example: with regular opioid use, higher doses are often needed over time to feel the same analgesic or euphoric effect.