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YR1 - Pharmacology SEM 2 > 21. Benzodiazepines > Flashcards

21. Benzodiazepines Flashcards

1
Q

On which neurotransmitter do Benzodiazepines work on?

A

Benzodiazepines are centrally acting medications which potentiate the actions of gamma amino butyric acid (GABA), the major inhibitory transmitter within the brain.

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2
Q

Give 3 examples of Benzodiazepines.

A

Benzodiazepines

  1. Diazepam
  2. Nitrazepam
  3. Temazepam
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3
Q

What are the 5 pharmacological and therapeutic actions of benzodiazepines?

A

Benzodiazepines

Pharmacological and therapeutic actions of benzodiazepines include:

  1. Hypnotic → puts you to sleep
  2. Anxiolytic → anti-anxiety
  3. Anticonvulsant → epileptic
  4. Skeletal muscle relaxation → eg. back pain due to muscular spasm
  5. Anterograde amnesia → Dose dependent effect = don’t lay down new memories = don’t remember what happens when under the influence of the drug
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4
Q

What is Gamma Amino Butyric Acid (GABA)?

Where is it found in the body?

What is its action?

Which cells release GABA?

A

Gamma Amino Butyric Acid (GABA)

  • GABA is found primarily in the brain
  • It is the major inhibitory transmitter in the CNS
  • It acts as an inhibitory transmitter in many parts of the CNS
  • About 20% of neurones in the CNS are GABAergic (they release GABA)
  • Virtually all neurons in the CNS are sensitive to the inhibitory effects of GABA
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5
Q

On which 2 receptors does GABA work?

A

GABA acts on two different types of receptors:

1) GABAA receptors = ligand-gated ion channel receptors
* Fastest receptors in body
2) GABAB receptors = G protein-coupled receptors

  • Most receptor in body are GPCRs
  • Slower than ligand-gated
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6
Q

What happens when GABA binds to GABAA receptors?

A
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7
Q

What happens when a G-Protein Coupled Receptor (GPCR) is stimulated?

A
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8
Q

What type of receptors are GABAA Receptors?

What is the GABAA Receptor channel selectively permeable to?

What is the effect on the cell?

A

GABAA Receptors

  • GABAA receptors are ligand-gated ion channel receptors
  • The GABAA receptor channel is selectively permeable to Cl- ions
  • Increasing the permeability and concentration of Cl- ions in the cell hyperpolarises the cell and reduces excitability
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9
Q

What is the structure of GABAA Receptors?

A

GABAA Receptor - Structure

  • They are pentamers made up of different subunits (alpha, beta, gamma, delta, epsilon, pi and theta).
  • 19 GABAA receptor subunits have been identified.
  • The most common configuration is α1β2γ2 arranged as α1-β2-α1-β2-γ2
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10
Q

Where do Benzodiazepines bind at GABAA Receptors?

A
  • Benzodiazepines potentiate the effects of GABA at some GABAA receptors depending on the subunit composition of the receptor
  • Benzodiazepines bind to a site on the GABAA receptor distinct from the GABA binding site
    • NOT agonists at the GABA binding site
  • Benzodiazepines facilitate the binding of GABA and increase its effects
  • Benzodiazepines increase the frequency of opening of GABA activated chloride channels
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11
Q

How do the following affect GABA at GABAA Receptors?

  • Benzodiazepines?
  • Barbiturates?
  • Alcohol?
A

GABAA Receptors

  • Benzodiazepines increase the frequency of opening.
  • Barbiturates increase the duration of the opening.
  • Alcohol increases both the frequency and the duration of the opening.
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12
Q

What is the pharmacological basis for the different therapeutic effects of Benzodiazepines?

A

Benzodiazepines

  • 19 GABAA receptor subunits have been identified
  • These are (α1-6, β1-3, γ1-3, δ, ε, θ, π and ρ1-3)
  • Various combinations occur in GABAA receptors in different parts of the brain.
  • Stimulation of these different receptors can produce different responses.
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13
Q

Which therapeutic effects of Benzodiazepines are attributed to the GABAΑ receptor subtype α1?

A

GABAΑ receptors containing the α1 subunit mediate the:

  • Hypnotic
  • Sedative
  • Anticonvulsant
  • Addictive effects
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14
Q

Which therapeutic effects of Benzodiazepines are attributed to the GABAΑ receptor subtype α2?

A

GABAΑreceptorscontainingthe α2 subunit mediate the anxiolytic effect.

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15
Q

Which therapeutic effects of Benzodiazepines are attributed to the GABAΑ receptor subtype α2, α3 and α5?

A

GABAΑ receptors containing the α2, α3 and α5 subunits mediate muscle relaxation.

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16
Q

Which GABAΑ receptor subtypes are responsible for the amnesic effects of benzodiazepines?

A

GABAΑ receptors containing the α1 and α5 subunits mediate the amnesic effects.

17
Q

Which 2 Benzodiazepines are used in the treatment of insomnia?

A

Benzodiazepines

Those used in the treatment of insomnia include:

  1. Nitrazepam
  2. Temazepam
18
Q

Which 3 Benzodiazepines are used in the treatment of anxiety?

A

Benzodiazepines

Those used in the treatment of anxiety include:

  1. Diazepam
  2. Oxazepam
  3. Alprazolam
19
Q

Which Benzodiazepine is used in the treatment of skeletal muscle spasm?

A

Benzodiazepines

Those used in the treatment of skeletal muscle spasm include:

  1. Diazepam
20
Q

Which 2 Benzodiazepines are used in the treatment of epilepsy and convulsions?

A

Benzodiazepines

Those used in the treatment of epilepsy and convulsions include:

  1. Clonazepam
  2. Diazepam
21
Q

How long should Benzodiazepams be used for?

A

As a general rule benzodiazepines should only ever be used for the shortest time possible (weeks rather than months).

22
Q

Which group of patients should you take care when prescribing Benzodiazepines to?

A

Take particular care in elderly patients who may experience excess sedation, confusion, ataxia, falls etc

23
Q

What is the “hangover effect” of benzodiazepines?

How is it fixed?

A

“Hangover effect” (morning drowsiness) may occur with the use of benzodiazepines as hypnotics

Solution = reduce dose + use shorter t1/2

e.g. change from nitrazepam (t1/2 16 - 48 hours) to temazepam (t1/2 5 - 15 hours)

24
Q

What are some of the different half lives of Benzodiazepines?

A
25
Q

What causes the wide variation of half lives of different benzodiazepines?

A

= Pharmacokinetics - Metabolism

  • eg. Phase 1 then Phase 2 reactions
26
Q

What is Tolerance?

Which effects of Benzodiazepines can you build tolerance towards?

A

Tolerance = A reduced response to the same dose OR the need to increase dose to achieve same effect.

Benzodiazepines - Tolerance

  • Tolerance has been reported to develop fairly rapidly to the hypnotic effect of benzodiazepines
  • Tolerance towards the anxiolytic effects, when detected, appears to develop more slowly
  • Inconsistent findings regarding the need to increase the dose
  • Mechanism by which tolerance develops is not fully understood
27
Q

What is a major adverse effect/concern with the use of Benzodiazepines?

How does this manifest (symptoms?)

A

Benzodiazepine use may result in dependence

  • May occur following longer-term use of therapeutic doses, and rarely in some patients following short term use e.g. 2-4 weeks
  • Manifests as a withdrawal syndrome following the abrupt cessation of the benzodiazepine
  • Symptoms may include insomnia, anxiety, nervousness, irritability, palpitations etc
    • Withdrawal symptoms are very similar to the symptoms benzodiazepines are used to treat
      • Need to be able to determine if WSs or just underlying pathology resurfacing
  • Can’t go cold turkey!
  • Abrupt withdrawal following long term use of high doses may also produce convulsions
28
Q

What affect does a benzos half life have on the onset of withdrawal symptoms?

How long do WSs last?

A

Benzodiazepines - Tolerance & WSs

  • Withdrawal symptoms occur earlier (1-2 days) with short t1/2 drugs
    • e.g. oxazepam, temazepam
  • May take up to 5 days to appear with longer t1/2 drugs
    • e.g. diazepam
  • Abrupt withdrawal of short t1/2 drugs may produce more intense symptoms
  • Withdrawal duration is variable and can be up to 8 weeks
29
Q

How are withdrawal symptoms relieved?

How can they be avoided?

A

Withdrawal symptoms may be relieved by recommencing the benzodiazepine.

Avoiding Withdrawal Symptoms

  • When withdrawing therapy, dosage reduction should be gradual
    • e.g. 15% per week with monitoring of symptoms
  • Patients taking high doses for prolonged periods of short t1/2 drugs may be stabilised on an equivalent dose of diazepam (long t1/2), and the dose gradually reduced (10 -15%) per week
30
Q

What are 10 adverse effects of Benzodiazepines?

A

Benzodiazepines - Adverse effects

  1. Fatigue
  2. Drowsiness
  3. Confusion
  4. Memory impairment
  5. Cognitive impairment
  6. Muscle weakness
  7. Ataxia
  8. Dry mouth
  9. Constipation
  10. Drug interactions

Elderly patients are far more susceptible to the adverse effects of benzodiazepines (confusion, memory loss, ataxia, falls etc)

31
Q

Can you overdose on Benzodiazepines?

What are 5 symptoms?

What is the name of the benzodiazepine antagonist?

A

Benzodiazepine Overdose

  • Benzodiazepines have a high therapeutic index
    • How close the therapeutic dose is to the toxic dose
    • = Wide = fairly safe drug
  • Benzodiazepine overdose alone is generally not life threatening
    • BUT combination with other sedative products may be very serious - eg. alcohol
  • Symptoms
    1. Drowsiness
    2. Confusion
    3. Hypotension
    4. Coma
    5. Respiratory depression
  • Treatment is generally supportive
  • Benzodiazepine antagonist flumazenil is available, but is not used routinely
    • Has affinity but no intrinsic activity = competes with benzos at receptor binding sites = blocks effects
  • Activated charcoal can be considered if within 1-2 hours of overdose

YR1 - Pharmacology SEM 2 (8 decks)

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