doxylamine

Adjunctive therapy

Brands: UNISOM

Last reviewed 2025-12-30

Reviewed by PsychMed Editorial Team.

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Quick answers

What is doxylamine?
Doxylamine (brand Unisom SleepTabs and many generics) is a first-generation antihistamine marketed OTC as a sleep aid. It is also an ingredient in the prescription combination doxylamine/pyridoxine (Diclegis) used for nausea and vomiting of pregnancy (label/product-dependent).
What is UNISOM?
UNISOM is a brand name for doxylamine.
What is UNISOM (doxylamine) used for?
Label indications include: OTC sleep aid (product-dependent). Also used in combination with pyridoxine for nausea/vomiting of pregnancy (label; product-dependent).
What drug class is UNISOM (doxylamine)?
First-generation antihistamine (H1 antagonist) with sedating and anticholinergic effects; OTC sleep aid and antiemetic ingredient (doxylamine/pyridoxine).
What strengths does UNISOM (doxylamine) come in?
OTC sleep aid tablets are commonly 25 mg (product-dependent); label dosing is typically once nightly.

Snapshot

Primary label indications include: OTC sleep aid (product-dependent).
Class: Adjunctive therapy
Common US brands: UNISOM
Therapeutic drug monitoring not routinely recommended.
Last reviewed: 2025-12-30

Label indications

OTC sleep aid (product-dependent). Also used in combination with pyridoxine for nausea/vomiting of pregnancy (label; product-dependent).

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Clinical Highlights

Doxylamine (brand Unisom SleepTabs and many generics) is a first-generation antihistamine marketed OTC as a sleep aid. It is also an ingredient in the prescription combination doxylamine/pyridoxine (Diclegis) used for nausea and vomiting of pregnancy (label/product-dependent). Like other first-generation antihistamines, doxylamine is sedating and strongly Anticholinergic. Sedation is often the desired effect for sleep, but anticholinergic harms (confusion, constipation, urinary retention, blurred vision) can be clinically significant—especially in older adults and with polypharmacy (Beers/clinical).

Doxylamine has a relatively long half-life for an OTC sleep aid (~10 hours; longer in some 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 use of sedating antihistamines for chronic insomnia (weak recommendation). Treat doxylamine as a time-limited adjunct while addressing underlying insomnia drivers (mood, substances, pain, sleep apnea, circadian disruption).
Best fit is short-term, situational insomnia when a sedating OTC option is preferred and anticholinergic risk is low—not a default long-term strategy.
The compare view, doxylamine evidence feed, and doxylamine print page can help weigh OTC sleep aids against evidence-backed insomnia options.

Dosing & Formulations

OTC sleep-aid tablets are commonly 25 mg. One common label direction is 25 mg once nightly taken about 30 minutes before bed (product-dependent label). Because next-day impairment risk rises with longer half-life, avoid “middle-of-the-night catch-up dosing” and take only when a full sleep window is possible (clinical).

If insomnia persists beyond a short course, avoid open-ended nightly use; reassess for treatable drivers and prioritize CBT-I and evidence-based options rather than stacking sedatives (AASM/clinical).
In pregnancy, doxylamine is commonly used in combination with pyridoxine under clinician guidance (Diclegis; label/product-dependent); do not substitute OTC sleep-aid products without clarifying equivalence and dosing.

Monitoring & Risks

Sedation / next-day impairment: assess driving risk, falls, and daytime cognitive slowing; risk is higher in older adults and with polypharmacy (StatPearls/clinical). Anticholinergic effects (dry mouth, constipation, urinary retention, blurred vision): higher risk in older adults and those with urinary obstruction or glaucoma (Beers/clinical).

Cognitive effects: confusion and delirium can occur, especially in older adults; Beers Criteria guidance generally supports avoiding chronic first-generation antihistamines when possible (Beers).
Overdose risk: anticholinergic toxicity, seizures, rhabdomyolysis, and arrhythmias are described with large ingestions; avoid “dose chasing” and keep away from children (StatPearls/clinical).

Drug Interactions

Additive CNS/respiratory depression occurs with alcohol, opioids, benzodiazepines, sedating antipsychotics, and other hypnotics; avoid stacking sedatives when possible (clinical). Additive anticholinergic burden with other anticholinergics (tricyclics, low-potency antipsychotics, bladder antimuscarinics) increases delirium and urinary retention risk (clinical).

Practice Notes

Avoid chronic nightly doxylamine use in older adults when possible (Beers). If insomnia is persistent, prioritize CBT-I and treat comorbid contributors rather than escalating OTC sedatives. If next-day impairment is prominent, switch agents rather than increasing dose or adding additional sedatives to “counter” side effects.

Compare doxylamine with alternatives that have clearer chronic-insomnia evidence (e.g., DORAs, ramelteon, low-dose doxepin) and match choice to sleep-onset vs maintenance complaints.
Reassess for sleep apnea, alcohol/cannabis use, mood symptoms, and circadian disruption before escalating sedative intensity.

References

Doxylamine succinate (OTC sleep aid) tablets label — DailyMed (2025)
Diclegis (doxylamine/pyridoxine) Delayed Release Tablets Label — DailyMed (2024)
Clinical Practice Guideline for the Pharmacologic Treatment of Chronic Insomnia in Adults: An American Academy of Sleep Medicine Clinical Practice Guideline — Journal of Clinical Sleep Medicine (2017)
2023 American Geriatrics Society Updated Beers Criteria for Potentially Inappropriate Medication Use in Older Adults — Journal of the American Geriatrics Society (2023)
Doxylamine (StatPearls) — StatPearls Publishing (NCBI Bookshelf) (2025)