Pharmacological management of sleep disorders

Benzos & Z-Drugs - The GABA Boosters

• MoA: Potentiate GABA-A receptors, ↑ frequency of Cl⁻ channel opening → hyperpolarization & CNS depression.
• Agents:
  • Benzodiazepines: Temazepam, Triazolam. Less selective (also anxiolytic, myorelaxant).
  • Z-Drugs: Zolpidem, Zaleplon, Eszopiclone. More selective for α1-subunit; primarily hypnotic.
• Use: Short-term insomnia management (sleep onset & maintenance).
• Adverse Effects:
  • Tolerance, dependence, withdrawal.
  • Rebound insomnia.
  • Anterograde amnesia, daytime sedation.
  • ↑ Fall risk in the elderly.
  • ⚠️ Complex sleep behaviors (e.g., sleep-driving), esp. with Z-drugs.

⭐ Z-drugs (e.g., Zolpidem) have less effect on sleep architecture than benzodiazepines but still carry significant risks of dependence and complex sleep-related behaviors.

Orexin & Melatonin Agents - The Switch Flippers

• Suvorexant, Lemborexant
  • Mechanism: Dual Orexin Receptor Antagonists (DORAs). Block orexin-A & B from binding to OX1R & OX2R.
  • Physiology: Orexin system promotes wakefulness. DORAs inhibit this, acting as a "switch" to turn off arousal systems.
  • Use: Insomnia (sleep onset & maintenance).
  • Side Effects: Next-day somnolence, sleep paralysis, complex sleep behaviors.

• Ramelteon, Tasimelteon
  • Mechanism: Selective agonists for MT1 & MT2 melatonin receptors in the suprachiasmatic nucleus (SCN).
  • Ramelteon: For sleep-onset insomnia.
  • Tasimelteon: For non-24-hour sleep-wake disorder (e.g., in blind individuals).

⭐ Unlike benzodiazepines, melatonin agonists do not disrupt sleep architecture and have no risk of dependence, rebound insomnia, or withdrawal.

Narcolepsy Meds - The Wake-Up Crew

Primary goals: ↑ daytime wakefulness & ↓ cataplexy.

• Wakefulness-Promoting Agents (1st Line for EDS):

  • Modafinil & Armodafinil: Atypical stimulants with low abuse potential. Primary choice.
  • Solriamfetol: A dopamine-norepinephrine reuptake inhibitor (DNRI).
  • Pitolisant: A histamine H3-receptor antagonist/inverse agonist.

• For Cataplexy & EDS:

  • Sodium Oxybate (GHB): GABA-B agonist. Excellent for cataplexy, fragmented sleep, and EDS.
  • Antidepressants: TCAs, SSRIs, and venlafaxine are effective for cataplexy by suppressing REM sleep.

⭐ Sodium Oxybate carries a black box warning for CNS depression and abuse/misuse. Co-administration with alcohol or other sedatives is contraindicated due to severe respiratory depression risk.

Antidepressants & Others - The Off-Label Allies

• Trazodone
  • Low-dose antidepressant for insomnia; mechanism: H1 & 5-HT2A antagonism.
  • ⚠️ Risk of priapism.
• Doxepin (TCA)
  • Ultra-low-dose for sleep maintenance via potent H1 blockade.
• Mirtazapine
  • Sedating; useful for insomnia with depression or low appetite.
  • Side effects: ↑ appetite, weight gain.
• Ramelteon
  • Melatonin receptor agonist (MT1/MT2) for sleep-onset difficulty.
  • Not a controlled substance.
• Suvorexant

  ⭐ Dual Orexin Receptor Antagonist (DORA). It promotes sleep by blocking the wake-promoting signals of orexin neuropeptides.

High‑Yield Points - ⚡ Biggest Takeaways

• Benzodiazepines & Z-drugs (e.g., zolpidem) potentiate GABA-A receptors; carry risks of tolerance, dependence, and rebound insomnia.
• Ramelteon, a melatonin receptor agonist, is safe for sleep-onset insomnia, especially in elderly or substance abuse history.
• Suvorexant, an orexin receptor antagonist, is effective for both sleep onset and maintenance difficulties.
• Low-dose trazodone is frequently used for insomnia in depression; be aware of the rare risk of priapism.
• Modafinil is first-line therapy for the excessive daytime sleepiness of narcolepsy.