Chapter 12  ·  Module 2
Non-Benzodiazepine Hypnotics, Melatonin Agonists, and Orexin Antagonists
Three mechanistically distinct alternatives to benzodiazepines for insomnia
Z-Drugs: Comparative Profiles
AgentHalf-LifeBest ForKey FeatureCaution
Zolpidem1.5–2.5 hours (IR)Sleep onsetMost prescribed hypnotic in US. FDA lowered dose to 5 mg for women in 2013.Next-day driving impairment at 10 mg in women
Zaleplon~1 hourSleep onset; middle-of-night awakeningShortest duration. Can be taken if 4+ hours remain.No benefit for sleep maintenance
Eszopiclone~6 hoursOnset and maintenanceOnly Z-drug approved for both. Bitter taste in up to 34% of patients.Greater next-day sedation than zolpidem IR
Boxed Warning: All Z-Drugs

Complex sleep behaviors (sleepwalking, sleep-driving, activities with no memory of event) — 2019 FDA boxed warning. Risk increased by higher doses, alcohol, and other central nervous system depressants. Previous complex sleep behavior with any sedative-hypnotic: contraindication to use.

Three-Class Mechanism Comparison
Z-Drugs
GABA-A Positive Allosteric Modulators
  • Bind benzodiazepine site on GABA-A receptor
  • Relative alpha-1 subunit selectivity (sedation > anxiolysis)
  • Schedule IV; dependence possible
  • Complex sleep behavior risk (boxed warning)
  • On Beers Criteria for elderly
Ramelteon
Melatonin Receptor Agonist (MT1/MT2)
  • Mimics melatonin circadian signal; does not sedate
  • No GABA-A receptor activity
  • Not scheduled; no dependence potential
  • No complex sleep behavior warning
  • Sleep onset only; smallest effect size
  • Contraindicated with fluvoxamine (CYP1A2 inhibitor)
Suvorexant / Lemborexant
Dual Orexin Receptor Antagonists
  • Block orexin wake-promoting drive (remove arousal)
  • Preserve slow-wave and REM sleep architecture
  • Approved for onset and maintenance insomnia
  • Unique adverse effects: cataplexy-like episodes, sleep paralysis, hypnagogic hallucinations
  • Caution in obstructive sleep apnea
  • Schedule IV; lower abuse liability than Z-drugs
Drug Selection by Clinical Situation
Clinical SituationPreferred AgentRationale
Sleep-onset insomnia, general adultZolpidem IR or zaleplonRapid onset, short duration
Sleep-maintenance insomniaSuvorexant or lemborexantBest evidence for wake-after-sleep-onset reduction
Elderly patientRamelteon (preferred); lowest-dose Z-drug if neededNo dependence, not on Beers Criteria
Substance use disorder historyRamelteonNot scheduled; no abuse potential established
Sleep-onset and maintenance (combined)Eszopiclone or dual orexin receptor antagonistApproved for both complaint types
Comorbid depressionLow-dose doxepin (3–6 mg)Only antidepressant FDA-approved specifically for insomnia