What is tolerance?

• A. Needing lower doses over time
• B. Immediate effect
• C. Dependence only
• D. Needing higher doses over time for the same effect

Answer: (D)

Tolerance is when repeated exposure to a drug produces a smaller effect, so you need higher doses over time to achieve the same level of analgesia or other effect. This can arise from changes at the drug’s target receptors (receptor desensitization or downregulation) or from the body increasing the rate at which the drug is metabolized. In pain management with opioids, tolerance to analgesia often develops, which is why dose escalation is sometimes observed. It’s different from immediate onset or from dependence and withdrawal, which are separate phenomena. Needing lower doses over time would reflect sensitization, not tolerance. The pattern of requiring more drug over time to achieve the same effect is the defining feature.