Benzodiazepines are a class of medications that act as a central nervous system depressant.
They have a wide variety of uses including anxiolytic effects, or to relieve anxiety; as anticonvulsants, or to manage seizure disorders; as a hypnotic for insomnia; as an anesthetic; and to treat withdrawal syndromes.
They act by enhancing the main inhibitory neurotransmitter gamma-aminobutyric acid, or GABA, by binding to its receptor.
It’s pretty well-established that your brain’s really important. It controls your feelings, your movements, your sleep, your memory… It controls everything, whether you’re aware of it or not.
The cells that make up our brain are called neurons.
Neurons communicate with each other through neurotransmitters.
When one neuron is stimulated, it’ll release excitatory neurotransmitters like glutamate which bind to receptors on the next neuron. This causes the next neuron to depolarize and release its own excitatory neurotransmitters, propagating the signal throughout the brain.
Now, we also have inhibitory neurons that will shut down this chain of events.
These neurons release the main inhibitory neurotransmitter gamma-aminobutyric acid, or GABA, which binds to GABA receptors on other neurons. These receptors are large, multi unit complexes that form ligand-gated ion channels that open up to let Cl- ions into the cell.
The influx of negatively charged ions causes hyperpolarization, where the cell’s membrane potential becomes more negative, which means it’s much more difficult for it to depolarize and fire off an action potential, meaning it’s less responsive to stimuli.
Alright, now there are cases where neurons in the brain start sending out more excitatory signals than normal.
This can occur due to either too much excitation by the excitatory neurotransmitters, or too little inhibition by the inhibitory neurotransmitters like GABA.
Excessive excitatory signals can cause psychiatric disorders like anxiety, and neurological disorders like seizures and epilepsy.
Okay, so one way we can decrease the excitatory signals is by enhancing the effect of inhibitory neurons through medication like benzodiazepines.
They are composed of a benzene ring that consists of six carbon atoms fused to a diazepine ring that is made up of 5 carbon atoms and two nitrogen atoms.
They can be roughly divided into the long acting benzos like diazepam and chlordiazepoxide and short acting benzos, like midazolam, alprazolam, lorazepam, oxazepam, and temazepam. These medications target the GABAA receptors, but they bind at a seperate site than GABA.
When both benzodiazepine and GABA bind to their separate sites on the receptor, the Cl- ion channel opens more frequently and increases the intracellular chloride level.
Now, a similar group of medications called barbiturates also function by binding to GABAA receptors.
The important distinction is barbiturates cause the channels to open longer and unlike benzodiazepines, they can cause the channels to open even in the absence of GABA.
Alright, so benzodiazepines are indicated when the neurons get “super excited” and we want to calm them down like in anxiety disorders, or during a panic attack.
Benzodiazepines are also very effective anticonvulsants and are considered the treatment of choice for status epilepticus, which is when a person has over 5 minutes of ongoing seizures or multiple seizures without returning to normal in between.
Certain benzodiazepines are also used for anesthesia since we basically want to depress the function of the patient’s nervous system. For the same reason, they are an effective treatment for insomnia, but they decrease REM sleep.
Since alcohol and barbiturates also work by targeting GABAA receptors, benzodiazepines can be used to manage their withdrawal symptoms by decreasing their severity.
Finally, they are sometimes used as muscle relaxants to treat spasms, like those caused by cerebral palsy.
Moving on to side effects! Benzodiazepines can have some adverse effects even when used at therapeutic levels. And when it’s combined with alcohol or other medications that depress the nervous system, like barbiturates and antihistamines, the nervous system depression can get even more severe.
That said, benzodiazepines have relatively fewer and less severe side effects when compared to barbiturates. These include drowsiness, and decreased concentration, problem solving abilities, and reaction time. Due to this, they should not be taken before driving.