PS268 Chapter Notes - Chapter 5: Blood Vessel, Neuroglia, Blood Proteins
The Actions of Drugs
Mechanisms of Drug Action: Getting the Drug to the Brain
-the chemistry of drug molecules determines whether drugs act quickly or slowly
Lipid solubility:
-the tendency of a chemical to disolve in fat as opposed to water
-most psychoactive drugs dissolve to some extent in either water or lipids
-all psychoactive drugs reach brain tissue through bloodstream
Drug Distribution and Transport in the Blood:
-when drug enters bloodstream its molecules will often attach to a protein molecule in blood
(usually albumin)
-as long as a protein-drug complex exists, drug is inactive and cannot leave blood
-equilibrium is established b/w free (unbound) drug and protein-bound forms of drug in the
bloodstream
-as unbound drug moves across capillary walls to sites of action, protein-bound drug is
released to maintain proportion of bound-to-free molecules
-alcohol has low affinity for binding w plasma proteins thus exists bloodstream primarily
unbound
Document Summary
Mechanisms of drug action: getting the drug to the brain. The chemistry of drug molecules determines whether drugs act quickly or slowly. The tendency of a chemical to disolve in fat as opposed to water. Most psychoactive drugs dissolve to some extent in either water or lipids. All psychoactive drugs reach brain tissue through bloodstream. When drug enters bloodstream its molecules will often attach to a protein molecule in blood (usually albumin) As long as a protein-drug complex exists, drug is inactive and cannot leave blood. Equilibrium is established b/w free (unbound) drug and protein-bound forms of drug in the bloodstream. As unbound drug moves across capillary walls to sites of action, protein-bound drug is released to maintain proportion of bound-to-free molecules. Alcohol has low affinity for binding w plasma proteins thus exists bloodstream primarily unbound. Thc have high affinity for bonding and only small fraction is free to enter brain/other tissues. =higher dose required to reach effective tissue concentration.
