PS268 Chapter Notes - Chapter 5: Central Nervous System Depression, Pharmacokinetics, Cross-Tolerance
Mechanisms of Tolerance and Withdrawal Symptoms
-the effect of a drug is proportional to its concentration at its site of action, increasing with
increasing doses
-over time with repeated use, the drug effect does not reach the predicted effect based on
dose and the drug effects are decreased (tolerance)
A reduced drug response can come about through at least 3 mechanisms: drug disposition
tolerance, behavioural tolerance, pharmacodynamic tolerance
-through any of these, the dose-response curve is shifted to the right, resulting in the same
dose having less effect or a greater dose being required to produce the same effect
Drug Disposition Tolerance:
-use of a drug increases the drug's rate of metabolism or excretion
-also called pharmacokinetic tolerance
-amphetamine is excreted unchanged in the urine, making the urine more acidic increases
the rate of excretion
Behavioural Tolerance:
-when the use of a drug interferes w normal behavioural functions, individuals learn to adapt
to the altered state of their nervous system and therefore compensate somewhat for the
impairment
Document Summary
The effect of a drug is proportional to its concentration at its site of action, increasing with increasing doses. Over time with repeated use, the drug effect does not reach the predicted effect based on dose and the drug effects are decreased (tolerance) A reduced drug response can come about through at least 3 mechanisms: drug disposition tolerance, behavioural tolerance, pharmacodynamic tolerance. Through any of these, the dose-response curve is shifted to the right, resulting in the same dose having less effect or a greater dose being required to produce the same effect. Use of a drug increases the drug"s rate of metabolism or excretion. Amphetamine is excreted unchanged in the urine, making the urine more acidic increases the rate of excretion. When the use of a drug interferes w normal behavioural functions, individuals learn to adapt to the altered state of their nervous system and therefore compensate somewhat for the impairment.
