Pharmacodynamics · Pharmacology

A 'Spare Receptor' population exists when:

  1. The maximal drug response occurs at less than full receptor occupancy
  2. A drug cannot bind to any receptors in the tissue
  3. All receptors must be occupied to see any effect
  4. The drug binds preferentially to plasma proteins instead of tissue receptors
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Correct answer: The maximal drug response occurs at less than full receptor occupancy

Spare receptors increase the sensitivity of a cell to an agonist. If a system has spare receptors, the $EC_{50}$ of the drug will be lower than its $K_d$ (the concentration needed to occupy 50% of receptors).

Difficulty: Medium Question 11 of 20

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