Introduction

Benzodiazepines are an important class of medicines.

They have been around for a very long time, as far back as the mid-1950s. Back then it was Leo Sternbach – a Polish chemist – who was researching tranquilisers when, almost accidentally, he came across what would become known as chlordiazepoxide; the first benzodiazepine.

Benzodiazepines have since flourished – branching further and faster, never bearing more clinical relevance than their use today.

They are used in the treatment of a wide range of conditions:

  • Seizures
  • Anxiety disorders
  • Panic disorders
  • Insomnia
  • Sedation
  • Agitation
  • Alcohol dependence

Of course, not all benzodiazepines have the same duration of effect.

Some benzodiazepines are short-acting, while others are intermediate and long-acting. This classification has clinical significance. For example – long-acting benzodiazepines, such as diazepam, accumulate in the elderly. They also accumulate more in patients with hepatic dysfunction.

Recalling this classification of benzodiazepines is difficult, but not impossible.

Each benzodiazepine comes with their own half-life and, through this half-life, we can determine how long its effect is likely to last. Some benzodiazepines – again, let’s consider diazepam – have long-acting, active metabolites; in this case, desmethyldiazepam. Always keep these metabolites in mind.

Below, we review some clever benzodiazepine mnemonics that help you remember this important, clinically-relevant classification.

Short-acting benzodiazepines

There are four short-acting benzodiazepines we consider:

  • Alprazolam – used in the treatment of anxiety and panic disorders.
  • Triazolam – predominantly used to treat severe insomnia.
  • Oxazepam – insomnia and alcohol withdrawal.
  • Midazolam – procedural sedation and anesthesia.

Of course, these indications are not exhaustive. For example, midazolam may be used to treat insomnia. However, the most common indications are listed. Short-acting benzodiazepines have an approximate half-life between 1 and 15 hours.

Below, we find that all four medicines align to produce the “ATOM” pharmacology mnemonic.

short-acting benzodiazepines

Intermediate-acting benzodiazepines

Let’s consider the following four intermediate-acting benzodiazepines:

  • Temazepam – used to treat insomnia.
  • Lorazepam – used to treat anxiety and seizures.
  • Clonazepam – seizures and panic disorder
  • Estazolam – short-term treatment of insomnia.

Again, these indications are not necessarily exhaustive. Intermediate-acting benzodiazepines have an approximate half-life of between 15 and 40 hours.

A great way of remembering intermediate-acting benzodiazepines is to think about the pharmacology mnemonic, “Best TLC”.

Long-acting benzodiazepines

Finally, let’s now consider the following four long-acting benzodiazepines:

  • Diazepam – anxiety, seizures, alcohol withdrawal, muscle spasm, sedation.
  • Flurazepam – insomnia.
  • Clorazepate – anxiety disorders, insomnia, alcohol withdrawal seizures.
  • Chlordiazepoxide – anxiety and alcohol withdrawal syndrome.

Again, these indications are not necessarily exhaustive. Long-acting benzodiazepines have an approximate half-life of between 40 and 260 hours.

Always think about the pharmacology mnemonic, “FC-DC” – easy to recall because both “C” elements related to “clor/chlor”. Diazepam and flurazepam are among the most widely known benzodiazepines, making this mnemonic that much easier.

Liver metabolism mnemonic

Before we finish up, let’s briefly talk about benzodiazepines and liver disease.

Many benzodiazepines, particularly the long-acting examples, can accumulate to quite a significant extent in the liver – an effect which can prove hazardous in patients with liver failure.

As a result, some benzodiazepines are safer than others – the LOT medicines:

  • Lorazepam
  • Oxazepam
  • Temazepam

Because LOT members are not metabolised to active compounds, their kinetics, become a lot more predictable in patients with liver disease because their half-life remains more-or-less constant.

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