Tolerance and Sensitization

• Repeated administration of a drug can alter its subsequent effectiveness

  • Tolerance: Repeated drug administration results in diminished drug effect (or requires increased dosage to maintain constant effect)
  • Sensitization: Repeated drug administration results in heightened drug effectiveness

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Withdrawal effects are often the opposite of the drug effect and often accompanies tolerance

Tolerance can reflect decreased drug-receptor binding, decreased numbers of receptors, or reduced postsynaptic action of the drug

More and more (higher dosage) is required to get the same effect as the original dose; decreased effectiveness=tolerance

Sensitization is increase in the effectiveness of the drug