Sedative-Hypnotics

On this page

Introduction & Classification - Sleepy Science Sorted

  • Sedatives: ↓CNS activity, reduce anxiety, exert calming effect.
  • Hypnotics: Induce drowsiness, facilitate onset & maintenance of sleep.
  • Dose-dependent effects: Sedation → Hypnosis → Anesthesia → Coma.
  • Sleep Physiology: NREM (restorative), REM (dreams). GABA (major inhibitory NT).
  • Classification:
    • Benzodiazepines (BZDs): Diazepam, Lorazepam. (Safer profile).
    • Barbiturates: Phenobarbital. (Enzyme inducers, ⚠️ High risk).
    • Non-BZDs (Z-drugs): Zolpidem, Zaleplon. (Act on BZ1/ω1).
    • Melatonin Agonists: Ramelteon. (No abuse potential).
    • Orexin Antagonists: Suvorexant. (Targets wakefulness).

⭐ BZDs increase frequency of Cl- channel opening; Barbiturates increase duration of opening and can directly activate Cl- channels at high doses.

Benzodiazepines - Chill Pills Unpacked

  • Mechanism: Bind BZD site on GABA-A receptor → ↑ frequency Cl⁻ channel opening → potentiate GABA. 📌 "Ben likes Frequent Clubs".
  • Effects: Anxiolytic, sedative, hypnotic, anticonvulsant, muscle relaxant, anterograde amnesia.
  • Key BZDs:
    Drugt½ (hrs)MetabolismPrimary Uses
    Diazepam20-100CYP P450 (active met)Anxiety, status epilepticus, muscle spasm
    Lorazepam10-20GlucuronidationAnxiety, seizures, pre-anesthetic
    Oxazepam5-15GlucuronidationAnxiety (safer: elderly, liver disease)
    Midazolam1.5-3.5CYP P450Sedation, anesthesia induction
  • Adverse Effects: Drowsiness, ataxia, dependence, withdrawal, respiratory depression (↑ with alcohol).
  • Antidote: Flumazenil.

⭐ Lorazepam, Oxazepam, Temazepam (📌 LOT) bypass Phase I metabolism (direct glucuronidation); safer in elderly/liver disease.

Barbiturates - Old School Knockouts

  • Mechanism: Bind GABA-A receptor, ↑ duration of $Cl^-$ channel opening. 📌 Barbi-DURATESDURATion.
  • Types (Duration of Action):
    • Ultra-short: Thiopental (IV anesthesia induction).
    • Short/Intermediate: Pentobarbital, Secobarbital (insomnia - largely obsolete).
    • Long: Phenobarbital (anticonvulsant, neonatal jaundice).
  • Adverse Effects: Severe CNS/respiratory depression, high dependence/tolerance, potent CYP450 enzyme induction (drug interactions), paradoxical excitement.
  • ⚠️ No specific antidote; supportive care crucial.

⭐ Contraindicated in acute intermittent porphyria (AIP) due to induction of ALA synthase enzyme.

Non-BZDs & Novel Agents - Zzzs & Beyond

  • Z-Drugs: Selective BZ1 (ω1) receptor agonists on GABA-A. 📌 "Zzz-drugs help you catch Zzzs selectively."
    DrugOnsetDurationKey Notes
    ZolpidemRapidShort (2-3h)Sleep onset/maintenance; less hangover, amnesia risk
    ZaleplonVery RapidUltra-short (~1h)For sleep initiation; minimal next-day sedation
    EszopicloneRapidInt. (~6h)For sleep onset/maintenance; common metallic taste
  • Ramelteon: Melatonin MT1/MT2 agonist. No dependence/abuse potential. For sleep-onset insomnia.
  • Suvorexant: Dual Orexin Receptor Antagonist (DORA). Blocks wakefulness signals.

⭐ Z-drugs' BZ1 selectivity results in fewer anxiolytic, muscle relaxant, and anticonvulsant effects compared to traditional benzodiazepines.

Clinical Use & Caveats - Dosing Do's & Don'ts

  • Uses: Insomnia (short-term), anxiety, seizures, anesthesia.
  • Dosing:
    • Do: Lowest effective dose, shortest duration. Gradual taper.
    • Don't: Abrupt stop (withdrawal risk). Avoid in elderly (↑ falls, confusion) & pregnancy. No alcohol.
  • Caveats:
    • Tolerance, dependence, withdrawal (can be severe).
    • Respiratory depression (additive with opioids/alcohol).
    • Anterograde amnesia (BZD).
    • 📌 "Z-Z-Z" drugs for sleep: Zolpidem, Zaleplon, EsZopiclone - less dependence than BZDs.

Flumazenil is the antidote for benzodiazepine overdose; it competitively antagonizes BZD binding at GABA-A receptors.

High‑Yield Points - ⚡ Biggest Takeaways

  • Benzodiazepines: Potentiate GABA-A (↑ frequency of Cl⁻ channel opening). Antidote: Flumazenil for overdose.
  • Barbiturates: Potentiate GABA-A (↑ duration of Cl⁻ channel opening), are strong enzyme inducers, no specific antidote.
  • Z-drugs (Zolpidem, Zaleplon): Selective for α1-GABA-A receptors, treat insomnia, generally lower dependence risk.
  • Buspirone: 5-HT1A partial agonist for chronic anxiety; non-sedating, slow onset of action.
  • Ramelteon: Melatonin MT1/MT2 receptor agonist for sleep-onset insomnia; non-GABAergic mechanism.
  • Suvorexant: Orexin receptor antagonist, promotes sleep by blocking wakefulness signals.

Practice Questions: Sedative-Hypnotics

Test your understanding with these related questions

Which drug selectively acts on GABA-A receptors to induce sleep with minimal effects on sleep architecture?

1 of 5

Flashcards: Sedative-Hypnotics

1/10

Diphenhydramine and meclizine (1st generation H1 receptor blockers) may cause significant _____ and have significant anti-muscarinic properties

TAP TO REVEAL ANSWER

Diphenhydramine and meclizine (1st generation H1 receptor blockers) may cause significant _____ and have significant anti-muscarinic properties

sedation

browseSpaceflip

Enjoying this lesson?

Get full access to all lessons, practice questions, and more.

Start Your Free Trial