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Brand: UNISOM
Published 2025-12-23 · Last reviewed 2025-12-30 · 5 references
Content sourced from FDA labeling (DailyMed) and peer-reviewed literature.
Doxylamine is a first-generation antihistamine marketed OTC as a sleep aid (e.g., Unisom SleepTabs and many generics). It is also used in the prescription combination doxylamine/pyridoxine (Diclegis) for nausea and vomiting of pregnancy (label/product-dependent).
Sedation is expected and often the reason it is used for sleep, but doxylamine is also strongly Anticholinergic. That increases constipation, urinary retention, blurred vision, and delirium risk, especially in older adults and in polypharmacy (Beers/clinical).
Doxylamine has a relatively long half-life for an OTC sleep aid (~10 hours; longer in older adults), increasing the risk of next-day grogginess, falls, and impaired driving (StatPearls/clinical).
Evidence for chronic insomnia benefit is limited. The AASM guideline recommends against routine sedating antihistamine use for chronic insomnia (weak recommendation), so treat doxylamine as a time-limited adjunct while addressing underlying drivers and prioritizing CBT-I.
The doxylamine compare view, evidence feed, and print page support side-by-side review and patient-friendly handouts for safe, time-limited use.
Doxylamine is inexpensive and widely accessible OTC, which can encourage chronic nightly use without reassessment. In older adults, Beers Criteria guidance generally supports avoiding chronic first-generation antihistamines because anticholinergic harms often outweigh benefits.
View labelExactRefer to the Glossary entry on Neurotransmitters for background on receptor systems involved in serious mental illness.
H1 antagonism produces sedation (central histamine blockade) and reduces allergic symptoms.
Antimuscarinic (anticholinergic) activity contributes to dry mouth, constipation, urinary retention, blurred vision, and delirium risk.
Sedation can help with sleep onset, but repeated nightly use does not treat the underlying insomnia system and can lead to diminished benefit or “polypharmacy creep” (clinical).