Pharmacology and Toxicology: Sedatives, Hypnotics, and CNS Stimulants

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Questions and Answers

What is the consequence of taking high doses of benzodiazepines?

  • Enhanced REM sleep
  • Coma and respiratory depression (correct)
  • Respiratory stimulation
  • Increased slow-wave sleep

What is the mechanism of action of benzodiazepines?

  • Activate GABA receptors without GABA presence
  • Directly hyperpolarize neuronal membranes
  • Inhibit GABA binding and decrease chloride channel opening
  • Bind to a BZ allosteric site and increase chloride channel opening (correct)

What is a characteristic of benzodiazepines compared to barbiturates?

  • They have no ceiling effect
  • They have a similar effect on sleep patterns
  • They have a greater margin of safety (correct)
  • They have a smaller margin of safety

What is the effect of benzodiazepines on sleep patterns?

<p>They reduce slow-wave sleep and REM sleep (C)</p> Signup and view all the answers

What is a therapeutic use of benzodiazepines?

<p>Short-term management of anxiety disorders (C)</p> Signup and view all the answers

What is a characteristic of oxazepam, temazepam, and lorazepam?

<p>They are metabolized by phase II conjugation (D)</p> Signup and view all the answers

What is the mechanism of action of barbiturates?

<p>They bind to an allosteric site on the GABA A receptor–chloride ion channel and increase the affinity of the receptor for GABA (A)</p> Signup and view all the answers

What is the main therapeutic use of thiopental?

<p>Short IV anesthetic in short procedures (B)</p> Signup and view all the answers

What is a characteristic of barbiturates that distinguishes them from benzodiazepines?

<p>They have a GABA-mimic action (A)</p> Signup and view all the answers

What is a contraindication for the use of barbiturates?

<p>Acute intermittent porphyria (D)</p> Signup and view all the answers

What is a side effect of barbiturates?

<p>Rebound insomnia after discontinuation (A)</p> Signup and view all the answers

What is the classification of phenobarbitone?

<p>Long acting (C)</p> Signup and view all the answers

What is the use of phenobarbital in neonates?

<p>Treatment of hyperbilirubinemia (A)</p> Signup and view all the answers

Why are barbiturates limited in their therapeutic use?

<p>Due to their strong sedative effects (B)</p> Signup and view all the answers

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Study Notes

Sedatives, Hypnotics, and CNS Stimulants

Barbiturates

  • Classification: Ultrashort acting (Thiopental), Short acting (Pentobarbitone), Long acting (Phenobarbitone)
  • Mechanism of Action: Bind to an allosteric site on the GABA A receptor–chloride ion channel, increasing the affinity of the receptor for GABA, opening chloride channel, and enhancing hyperpolarization of neurons
  • Therapeutic uses:
    • Anesthesia: Thiopental is used as a short IV anesthetic in short procedures
    • Anticonvulsant: Phenobarbital is used in the treatment of grand mal epilepsy
    • Neonatal jaundice: Phenobarbital is used in the treatment of hyperbilirubinemia in neonates (physiological jaundice)
  • Adverse effects:
    • Tolerance and dependence
    • Sedation and hangover effect
    • Rebound insomnia after discontinuation
    • Induce the rate-limiting enzyme in porphyrin biosynthesis, making them contraindicated in acute intermittent porphyria
    • Acute poisoning may occur at high doses, leading to coma and respiratory depression
  • Drug interactions: Microsomal enzyme inducers

Benzodiazepines

  • Classification: Short acting (Triazolam, Midazolam), Intermediate acting (Temazepam, Lorazepam, Oxazepam), Long acting (Diazepam, Clonazepam)
  • Mechanism of Action: Bind to a BZ allosteric site, facilitating GABA binding and increasing the frequency of chloride channel opening, leading to neuronal membrane hyperpolarization
  • Characteristics:
    • Great margin of safety compared to barbiturates
    • Can produce anterograde amnesia, useful for stressful procedures
    • Reduce slow-wave sleep and REM sleep, disrupting sleep patterns
  • Pharmacokinetics:
    • Oxazepam, Temazepam, and Lorazepam are metabolized only by phase II conjugation, making them safer for elderly patients
  • Therapeutic uses:
    • Anxiety disorders: effective for short-term management

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