Benzodiazepines are classified according to their duration of action:
- Duration ultra short, less than 6 hours, referred to as hypnotics;
- Duration short, between 12 and 18 hours, indicated as anxiolytics and hypnotics;
- Duration average, 24 hours, referred to as anxiolytics and antidepressants;
- Duration long, between 24 and 48 hours, indicated above all as anxiolytic, but also as anticonvulsants, since the increase in the inhibitory signal of GABA reduces the excitability of the cell.
Pharmacodynamic characteristics of benzodiazepines:
- The administration takes place orally or intravenously, never intramuscularly since in this case the absorption of the benzodiazepines would not be constant;
- The half-life time varies from drug to drug, so as to guarantee the desired effect;
- The fat solubility varies according to the depressing action to be carried out, the higher it is and the greater the depressing action at the level of the CNS;
- Being fat-soluble drugs, benzodiazepines are able to cross the blood-brain barrier and spread into breast milk;
- The more complex drugs have active metabolites with half-lives longer than the original compound (for example Oxazepam is an active metabolite of Diazepam);
- Elimination occurs mainly via the kidney.
How do benzodiazepines work?
The inhibitory neurotransmitter GABA interacts with two different receptors, the channel A receptor and the B receptor; the interaction with the GABA A receptor is favored by the passage of chlorine ions, this involves a depolarization of the cell membrane and a consequential reduction of cellular excitability. Benzodiazebines bind to the allosteric site of the GABA A receptor, facilitating the passage of chlorine ions, so as to enhance the inhibitory signal of GABA; this action at the central level results in a general depression of the excitability of the neurons.
The hypnotic effects of benzodiazepines can occur in the different stages of the sleep phase, in fact they can: reduce the duration of stage 1 and limit the number of nocturnal awakenings; extend the duration of stage 2 and reduce the duration of stages 3 and 4; to maintain the REM phase longer, which instead is completely eliminated by "another important class of hypnotic drugs, the barbiturates.
The hypnotic effect of benzodiazepines, being dose-dependent, goes against phenomena of pharmacological tolerance in the case of prolonged therapies; for this reason it is good to act with combined therapies and always under strict medical supervision. At very high dosages, the following can occur: mental confusion , diurnal psycho-motor deficits, anterograde amnesia (i.e. one can forget the events that occurred during the administration of the drug ... this adverse effect is very useful in the case of very invasive tests, such as endoscopies and bronchoscopies), rebaund insomnia following the suspension of the treatment with benzodiazepines, which can be even more severe in the case of short-term hypnotics.
Other articles on "Benzodiazepines - How Do Benzodiazepines Work?"
- Hypnotic-sedative drugs
- Antidepressants, drugs for depression
