Handbook of Drug Interactions

426 Jones
Fig. 13. Schematic representation of the -aminobutyric acid receptor (GABA A ) showing
its ion channel for chloride and the different binding sites for GABA, benzodiazepines,
barbiturates, and ethanol. When activated chloride ions flow into the cell, a chain of
events is triggered, ending in a pharmacological response.
the action of second messengers. Activation of NMDA receptors was also suggested as
a mechanism to explain some of the antisocial and aggressive behaviors seen in drunken
people (324).
Both during and after drinking ethanol, the drug distributes rapidly with the bloodstream
to reach all parts of the body. Ethanol passes the blood–brain barrier with ease.
After a single drink people experience feelings of mild euphoria, indicating that ethanol
molecules have already entered the brain and started to interfere with neurochemical
transmission. Ethanol, like other low-mol wt alcohols, is classified as a CNS depressant,
which means that other CNS depressant drugs (e.g., barbiturates and benzodiazepines)
are obvious candidates for pharmacodynamic interaction (325–328). Drug-induced
effects on the brain depend on the dose taken, the route of administration, lipid solubility,
and the degree of tolerance development in the individual.
When BAC is relatively low (