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LCRS 1 - Pharmacology COPY COPY > 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 COPY COPY (33 decks)

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