UNISOM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for UNISOM (UNISOM).
Antihistamine (H1-receptor antagonist); also exhibits anticholinergic and sedative properties.
| Metabolism | Hepatic via CYP450 (CYP2D6, CYP3A4); active metabolite monodesmethyldoxylamine. |
| Excretion | Primarily renal (hepatic metabolism to inactive metabolites, ~30–60% excreted in urine unchanged; small amounts in feces) |
| Half-life | Terminal elimination half-life is approximately 10–12 hours in adults; may be prolonged in elderly or hepatic impairment |
| Protein binding | Approximately 78–80% bound to plasma proteins (primarily albumin) |
| Volume of Distribution | Approximately 2.5–7.5 L/kg (large Vd indicating extensive tissue distribution, including central nervous system) |
| Bioavailability | Oral: approximately 80–90% (due to limited first-pass metabolism) |
| Onset of Action | Oral: 15–60 minutes for sedative effect; maximum effect 2–3 hours post-dose |
| Duration of Action | Sedative effects last 4–6 hours; antihistamine effects may persist up to 8–12 hours |
25 mg orally once daily at bedtime (doxylamine succinate).
| Dosage form | CAPSULE |
| Renal impairment | GFR < 30 mL/min: avoid use or reduce dose; specific guidelines not established. |
| Liver impairment | Child-Pugh class C: avoid use; class A or B: no specific adjustment but caution due to increased sedation risk. |
| Pediatric use | Weight-based: 1 mg/kg up to 25 mg orally at bedtime for children ≥12 years; children <12 years: not recommended. |
| Geriatric use | Start at 12.5 mg orally at bedtime; monitor for sedation, confusion, anticholinergic effects; avoid if possible due to increased risk of falls. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for UNISOM (UNISOM).
| Breastfeeding | Doxylamine is excreted into human breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.5 to 0.6. Theoretical risk of sedation or irritability in the infant exists; caution is advised. American Academy of Pediatrics considers it compatible with breastfeeding. |
| Teratogenic Risk | Unisom (doxylamine succinate) is classified as FDA Pregnancy Category A. Large controlled studies and epidemiological data show no increased risk of fetal abnormalities in any trimester. First trimester use is associated with no increased teratogenicity; second and third trimester risks are not increased. No fetal harm has been demonstrated. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to antihistamines","Concomitant use with MAOIs","Acute asthma attack","Narrow-angle glaucoma","Severe liver disease"]
| Precautions | ["Avoid alcohol and other CNS depressants","Use with caution in asthma, glaucoma, urinary obstruction, and BPH","May cause drowsiness, impair cognitive/motor function","Avoid in premature infants and neonates due to risk of SIDS"] |
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| Fetal Monitoring | No specific fetal monitoring required. Monitor maternal sedation level and anticholinergic effects. Avoid use in third trimester near term due to potential neonatal withdrawal symptoms if used chronically. |
| Fertility Effects | No adverse effects on fertility reported. In animal studies, no impairment of fertility was observed at clinically relevant doses. Human data are lacking but no known negative impact. |