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Sedative and Hypnotics: Classification, Mechanism, Therapeutic Uses, Adverse Effects, and Contraindications

Sedative and hypnotic drugs are primarily used to induce relaxation, reduce anxiety, and promote sleep. They are classified into benzodiazepines, barbiturates, non-benzodiazepine hypnotics, and other sedatives.

Classification

  • Benzodiazepines (e.g., diazepam, lorazepam)
  • Barbiturates (e.g., phenobarbital, secobarbital)
  • Non-benzodiazepine hypnotics (e.g., zolpidem, eszopiclone)
  • Other sedatives (e.g., antihistamines like diphenhydramine)

Mechanism of Action

  • Benzodiazepines: Enhance GABAergic activity at the GABA-A receptor, increasing chloride influx, leading to neuronal inhibition.
  • Barbiturates: Enhance GABAergic activity and directly open chloride channels in GABA-A receptors, causing CNS depression.
  • Non-benzodiazepine hypnotics: Selectively act on the GABA-A receptor alpha-1 subunit, promoting sleep with fewer side effects.

Therapeutic Uses

  • Benzodiazepines: Anxiety, insomnia, seizures, muscle relaxation, alcohol withdrawal
  • Barbiturates: Seizures, general anesthesia, insomnia
  • Non-benzodiazepine hypnotics: Short-term treatment of insomnia

Adverse Effects

  • Benzodiazepines: Drowsiness, memory impairment, dependence, respiratory depression
  • Barbiturates: Sedation, respiratory depression, dependence, overdose risk
  • Non-benzodiazepine hypnotics: Drowsiness, dizziness, tolerance, sleepwalking

Contraindications

  • Benzodiazepines: Acute narrow-angle glaucoma, severe respiratory disorders, pregnancy
  • Barbiturates: Hepatic impairment, respiratory depression, pregnancy
  • Non-benzodiazepine hypnotics: Sleep apnea, alcohol intoxication

Benzodiazepines vs. Barbiturates

    Benzodiazepines are preferred over barbiturates due to their wider therapeutic index, lower risk of overdose, fewer drug interactions, and a lower risk of addiction.

    Newer Non-Benzodiazepine Hypnotics

    Newer non-benzodiazepine hypnotics, such as zolpidem, eszopiclone, and zaleplon, are preferred for insomnia due to their specific action on the GABA-A receptor, reducing side effects and risk of dependence.