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LCRS 1 - Pharmacology > Anxiolytics, sedatives & hypnotics > Flashcards

Anxiolytics, sedatives & hypnotics Flashcards

1
Q

How is GABA metabolised?

A

GABA –> succinic semialdehyde (SSA) by GABA transaminase
SSA –> succinic acid by SSA dehydrogenase

Mitochondrial enzymes

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2
Q

What receptor is involved in GABAergic central neurotransmission?

A

GABA A receptor complex

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3
Q

Explain the GABA A receptor complex

A

Cl- ionophores - cause hyperpolarisation:

GABA modulin + GABA R protein + Barbiturate R protein + BDZ R protein in ring with Cl- channel protein in middle

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4
Q

What are the principal clinical uses of barbiturates?

A

Sedatives/hypnotics

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5
Q

What are the principal clinical uses of benzodiazepines?

A
  • Long-acting = anxiolytics, e.g. diazepam

- Short-acting = sedatives/hypnotics, e.g. temazepam

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6
Q

What are the adverse effects of barbiturates?

A
  • Enzyme inducers
  • Alter natural sleep (reduce REM) –> hangover, irritability
  • Depress respiration (tf low safety margins)
  • O.d. is lethal
  • Dependence - withdrawal syndrome
  • Tolerance
  • Potentiate effects of other CNS depressants (alcohol)w
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7
Q

What are the adverse effects of benzodiazepines?

A
  • Dependence - withdrawal syndrome (less intense than barbs)
  • Tolerance (less than barbs)
  • Potentiate other CNS depressants (alcohol, barbs)
  • Sedation, confusion, amnesia, ataxia
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8
Q

What drugs can increase free [plasma] of benzodiazepines?

A

Aspirin

Heparin

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9
Q

What are the advantages of benzodiazepines over barbiturates?

A
  • Mild effect on REM sleep
  • Don’t induce liver enzymes
  • Wide safety margin - overdose –> prolonged rousable sleep –> flumazenil
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10
Q

Why do the pharmacokinetics of benzodiazepines determine clinical use?

A
  • 20+ different benzodiazepines with very small differences in structure (3 rings, differ in R1, R2, R3, R4)
  • Same mechanisms of action
  • Similar potency
  • Tf pharmacokinetics determine clinical use
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11
Q

Summarise the pharmacokinetics of benzodiazpepines

A
  • Duration of action - varies - short or long-acting
  • Admin - peak [plasma] in 1h, well-absorbed orally, i.v. for status epilepticus
  • Distribution - binds PPs strongly, highly lipid soluble –> wide distribution
  • Extensive hepatic metabolism
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12
Q

What do hypnotics do?

A

Induce sleep

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13
Q

What do anxiolytics do?

A

Remove anxiety without impairing mental or physical activity

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14
Q

What do sedatives do?

A

Reduce mental and physical activity without producing loss of consciousness

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15
Q

What would an ideal benzodiazepine or barbiturate do?

A
  • Produce natural sleep
  • Not depress respiration
  • Have a wide margin of safety
  • Not produce hangovers or dependence
  • Not interact with other drugs
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16
Q

How does GABA binding affect the GABA A receptor complex?

A
  • Linkage of GABA receptor protein and BDZ receptor protein mediated by GABA modulin
  • Enhances BDZ binding
  • Momentary opening of Cl- channel
17
Q

How does BDZ binding affect the GABA A receptor complex?

A
  • Facilitates action of GABA on Cl- channel

- Enhances GABA binding - increases affinity

18
Q

How does Barb binding affect the GABA A receptor complex?

A
  • Enhances GABA binding
  • Direct agonist of Cl- channel
  • Enhances GABA action on Cl- channel
19
Q

How do barbiturates and benzodiazepines differ?

A
  • Different binding sites and mechanisms: BZs increase frequency of openings, barbs increase duration, opening caused by GABA
  • Barbs are less selective - other membrane effects, decrease excitatory transmission (may explain induction of surgical anaesthesia and low margin of safety)
20
Q

Why do benzodiazepines and barbiturates have no activity alone?

A

They are positive allosteric modulators

Only increase freq or duration of opening caused by GABA

21
Q

How is GABA synthesised?

A

Glutamate –> GABA by glutamate decarboxylase

22
Q

What are the clinical uses of benzodiazepines and barbiturates?

A
  • Sedatives/hypnotics
  • Anxiolytics
  • Anaesthetics - barbs
  • Anti-convulsants
  • Anti-spastics
23
Q

What can long-acting benzodiazepines be metabolised into?

A

Short-acting benzodiazepines

LCRS 1 - Pharmacology (33 decks)

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