Tolerance

Definition of Tolerance:

• It is a condition where increasing doses of a drug are required to produce the same effect previously achieved with a lower dose.

Types:

1. Pharmacokinetic:

   • Due to increased drug metabolism (e.g., enzyme induction).
   • Example: Barbiturates increase liver enzymes that metabolize drugs.

2. Pharmacodynamic:

   • Due to cellular changes at the receptor level (e.g., receptor downregulation or desensitization).

3. Cross:

   • Tolerance to one drug leads to tolerance to another similar drug.
   • Example: Tolerance to alcohol can lead to tolerance to benzodiazepines.

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