Reduced response to a medication after repeated use is known as?

• A. Tolerance
• B. Refractory
• C. Synergism
• D. Controlled Substances

Answer: (A)

The concept tested is tolerance. When a drug is used repeatedly, the body often adapts so the same dose produces a smaller effect. This diminished response can arise from changes at the drug’s target receptors (fewer receptors or receptors that are less responsive) or from increased drug metabolism that clears the drug faster. Clinically, this means you may need higher or more frequent doses to achieve the same effect, a phenomenon you’ll see with various medications used in the prehospital setting, such as opioids or sedatives.

It’s not about the disease resisting treatment (that would be refractoriness), nor about two drugs producing a greater combined effect (that’s synergism), and it’s not a regulatory category (controlled substances). A rapid subset of this concept, tachyphylaxis, describes a particularly quick drop in response after repeated administration.