Sensitization refers to what phenomenon in pharmacology?

• A. A decreased response after repeated exposure
• B. An increased response after repeated exposure
• C. No change in response
• D. A delayed onset

Answer: (B)

Sensitization is an increased response after repeated exposure to the same drug dose. With each subsequent administration, the nervous system becomes more responsive, so the effect is amplified even though the dose hasn’t changed. This is the opposite of tolerance, where the effect diminishes with repeated use and a larger dose is needed to achieve the same effect. Mechanisms can include heightened receptor sensitivity or signaling efficiency, greater neurotransmitter release, and longer-lasting changes in neural pathways that reinforce the drug’s impact. A common example is repeated exposure to a stimulant, where locomotor activity or similar effects become more pronounced over time at the same dose. The other options describe decreased response, no change, or a delayed onset, none of which capture the idea of an enhanced effect with repeated exposure.