Sedative-Hypnotic Drugs Chapter 22

Introduction to Sedative-Hypnotic Drugs

• Sedative drugs (anxiolytics) alleviate anxiety and promote calmness.
• Hypnotic drugs induce drowsiness, assisting with sleep onset and maintenance.
• Increased doses lead to more pronounced central nervous system (CNS) depression.

Types of Sedative-Hypnotics

• Major drug categories include:
  • Benzodiazepines: Serve as anxiolytics and hypnotics.
  • Barbiturates: Limited to anesthesia and epilepsy management.
  • Miscellaneous agents.

Related Drugs with Sedative-Hypnotic Effects

• β-blockers (e.g., Propranolol).
• Antipsychotics and antidepressants (including SSRIs, TCAs, venlafaxine, duloxetine, MAOIs).
• Antihistamines:
  • Agonists include benzodiazepines, Zolpidem, zaleplon, and eszopiclone (selective at BZ1 site).
  • Antagonist: Flumazenil (blocks benzodiazepines but not barbiturates).
  • Inverse agonists can induce anxiety and seizures.

Pharmacokinetics of Benzodiazepines

• Benzodiazepines vary in duration of action: long, intermediate, and short-acting.
• Absorption: Lipid-soluble benzodiazepines penetrate the CNS rapidly.
• Distribution: Crosses the placental barrier; can affect neonates if administered pre-delivery.
• Metabolism: Biotransformation to water-soluble metabolites via phase 1 and 2 reactions.

Effects of Benzodiazepines

• Long-acting agents may convert to active metabolites with prolonged effects.
• Muscle relaxation and CNS depression can occur, particularly at high doses.
• Anterograde amnesia prevents memory formation while under influence.

Classification of Barbiturates

• Generalized CNS inhibition with significant respiratory and cardiovascular effects at therapeutic doses.
• Respiratory depression common, particularly fatal in overdoses; caution in patients with pulmonary issues.

Unwanted Effects of Benzodiazepines

• Tolerance: Reduced responsiveness leading to increased dosage for effect.
• Dependence: Risk of withdrawal symptoms after prolonged use; symptoms include rebound insomnia, anxiety, and CNS excitability.
• Adverse effects: Include drowsiness, impaired judgment, and diminishing motor skills; impacts driving and relationships.

Toxic Effects and Overdoses

• Barbiturate overdoses lead to severe respiratory and cardiovascular depression.
• Benzodiazepine overdoses are less likely to be fatal but still pose risks, especially in vulnerable populations.

Rationale for Clinical Use of Benzodiazepines

• Preferred for anxiety management over barbiturates due to:
  • Rapid onset.
  • Higher therapeutic index.
  • Flumazenil availability for overdose treatment.
  • Lower risk of drug interactions and minimal effects on cardiovascular/ autonomic systems.

Treatment Guidelines

• Alprazolam and clonazepam show greater efficacy in managing anxiety and phobias long-term.
• Benzodiazepines should be employed for severe anxiety only, with caution due to addiction potential; recommended for short durations.
• Antianxiety effects less prone to tolerance compared to hypnotic effects.

This quiz focuses on Chapter 22, which explores sedative-hypnotic drugs, including their effects as anxiolytics and hypnotics. Understand the relationship between normal CNS activity and sedation or hypnosis. Test your knowledge of these essential pharmacological agents.