What are benzodiazepines and how do they work?
Many benzodiazepines (BZs), sometimes called “benzos”, exist and are prescribed therapeutically for several physical and psychological conditions. Click here for a list of their names. They are central nervous system (CNS) depressants and psychoactive drugs which are also known as GABAergic agents, sedative-hypnotics, or minor tranquilizers.
Benzodiazepines work by enhancing a very important neurotransmitter called GABA (gamma-aminobutyric acid) at the GABA A receptor. This results in the sedative, hypnotic (sleep-inducing), anxiolytic (anti-anxiety), anticonvulsant, and muscle relaxant properties for which the drugs are prescribed.
GABA is the chief inhibitory neurotransmitter in the mammalian central nervous system. Its role is in reducing neuronal excitability and, in humans, it is also responsible for the regulation of muscle tone. If your nervous system was a car, GABA functions much like the “brakes”. When the “car” takes off speeding down the road (excitability of the nervous system), GABA functions as the “brakes” to calm and slow it down.
Without getting too technical, GABA sends its inhibitory message by binding at special sites called GABA-receptors on the outside of the receiving neuron. Once GABA is bound to the GABA-receptor, the neuron opens a channel which allows chloride ions to pass inside of the neuron. These negative chloride ions make the neuron less responsive to other neurotransmitters (norepinephrine [noradrenaline], serotonin, acetylcholine and dopamine) which would normally excite it. Benzodiazepines also bind to their own receptors (benzodiazepine receptors) that are situated on the GABA-receptor. Combination of a benzodiazepine at this site acts as a booster to the actions of GABA, allowing more chloride ions to enter the neuron, making it even more resistant to excitation.
This short (1:23) video explains this concept visually:
A simplified visual of how benzodiazepines (and barbiturates) work is illustrated in this simple animation video (1:57):
There are also various subtypes of benzodiazepine receptors, all of which have slightly different actions. The alpha 1 subtype is responsible for sedative effects, the alpha 2 for anti-anxiety effects, and both alpha 1 and alpha 2 (as well as alpha 5) for anticonvulsant effects. All benzodiazepines combine, to a greater or lesser extent, with all these subtypes and all enhance GABA activity in the brain.
What are Z-drugs and how are they similar to benzodiazepines?
Non-benzodiazepines, sometimes referred to as ‘Z-drugs’ or hypnotics, are also a class of psychoactive drugs that are very similar to the benzodiazepines. Many exist and are prescribed. Click here for a list of their names.
Most Z-drugs are approved and prescribed for ‘treating’ insomnia or sleep ‘disorders’. For this reason, they have very short half-lives ranging from 2-6 hours (in the non-elderly).
The pharmacodynamics (biochemical and physiological effects) of Z-drugs are almost identical to the benzodiazepine drugs. For this reason, the Z-drugs have similar effects and also risks to the benzodiazepines. Where the Z-drugs do differ from benzodiazepines is in their chemical structure, which makes them unrelated molecularly to benzodiazepines.
The nonbenzodiazepines are activators of the GABA-A receptor. Like the benzodiazepines, they exert their effects by binding to and activating the benzodiazepine site of the receptor complex. Many of the Z-drugs are subtype selective (see subtypes discussed above) and are therefore novel in that they can provide specific effects (e.g., hypnotics with no anxiolytic effects).
A review of the literature regarding hypnotics, including the nonbenzodiazepine Z-drugs, concluded that these drugs cause an unjustifiable risk to the individual and to public health and lack evidence of long-term effectiveness due to tolerance. The risks include dependence, accidents, and other adverse effects. Gradual discontinuation of hypnotics leads to improved health without worsening of sleep. If difficult interdose withdrawal symptoms arise between doses of these short-acting Z-drugs, sometimes a diazepam substitution taper may be necessary. It is preferred that the Z-drugs should be prescribed for only a few days at the lowest effective dose and avoided altogether wherever possible in the elderly.
Both benzodiazepines and Z-drugs are recommended for short-term use only and both classes of drugs can cause tolerance, interdose, physical dependence, and withdrawal upon discontinuation. They both require slow and gradual tapers to discontinue them properly as well.