Therapeutic Index · Pharmacology

Which change would widen the therapeutic index of a drug?

  1. Increase in ED50
  2. Decrease in LD50
  3. Increase in LD50 with constant ED50
  4. Decrease in ED50 with constant LD50
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Correct answer: Increase in LD50 with constant ED50

Therapeutic index equals LD50 divided by ED50. Increasing LD50 while keeping ED50 constant increases the ratio, thereby widening the therapeutic index. This indicates a greater margin of safety.

Difficulty: Medium Question 19 of 20

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