NROSCI 0081 Lecture Notes - Lecture 15: Drug Tolerance, Pharmacodynamics, Pharmacokinetics
23 Feb 2018
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O(cid:272)(cid:272)urs (cid:449)hen a su(cid:271)je(cid:272)t"s rea(cid:272)tion to a ps(cid:455)(cid:272)hoa(cid:272)ti(cid:448)e drug (cid:894)su(cid:272)h as a painkiller(cid:895) de(cid:272)reases after repeated exposure to that drug: larger doses are required to achieve the same effect. Drug tolerance can involve: physiological factors, pharmacodynamics (functional tolerance, pharmacokinetic, psychological (behavioral) drug tolerance. Reversible (stop taking it for a while) Dependent on dose, frequency of drug use, and setting (environment) May occur rapidly, after long periods of chronic use, or never. Not all effects of a drug show the same amount of tolerance (often true of side effects) Several different mechanisms explain our tolerance: functional (pharmacodynamics, metabolic (pharmacokinetic, behavioral (context specific, cross-tolerance. Changes in mechanisms that cause drug effect at the cellular level. Compensation for the continued presence of the drug: this is because the brain seeks homeostasis. Agonists down regulation (removing receptors in the post-synaptic membrane) Tolerance: need a greater dose to get the same effect. Can also change efficacy (same dose does not have the same drug effect)
