SILENOR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SILENOR (SILENOR).
Selective histamine H1 receptor antagonist; promotes sleep by antagonizing central histaminergic neurotransmission.
| Metabolism | Hepatic via multiple CYP450 isoenzymes, including CYP3A4, CYP2D6, CYP1A2, and CYP2C9. |
| Excretion | Primarily renal (approximately 60% as unchanged drug and metabolites), with 30% fecal elimination. |
| Half-life | Terminal elimination half-life is approximately 10 hours (range 8-15 hours) in healthy adults; prolonged in elderly and hepatic impairment. |
| Protein binding | <10% bound to plasma proteins (albumin). |
| Volume of Distribution | 0.8-1.0 L/kg, indicating distribution into total body water. |
| Bioavailability | Oral: approximately 80%. |
| Onset of Action | Oral: 15-30 minutes to sleep onset. |
| Duration of Action | Approximately 6-8 hours; residual sedation may occur in some patients. |
6 mg orally once daily at bedtime, not to exceed 6 mg/day.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment (CrCl <15 mL/min) or ESRD. |
| Liver impairment | Contraindicated in Child-Pugh class C. For Child-Pugh class A or B: use with caution; consider reduced dose of 3 mg once daily. |
| Pediatric use | Not approved for use in pediatric patients <18 years; safety and efficacy not established. |
| Geriatric use | Lower initial dose of 3 mg once daily recommended due to increased risk of impaired motor/cognitive function; maximum dose 6 mg/day. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SILENOR (SILENOR).
| Breastfeeding | Doxylamine is excreted into breast milk in small amounts; M/P ratio not established. Use with caution; monitor infant for drowsiness, irritability, and feeding difficulties. American Academy of Pediatrics considers compatible with breastfeeding. |
| Teratogenic Risk | First trimester: limited data; doxylamine succinate (the active ingredient in SILENOR) is an antihistamine with no well-established human teratogenicity; some studies suggest a weak association with oral clefts, but overall risk is low. Second and third trimesters: no known fetal structural risks; avoid near term due to potential for neonatal respiratory depression and withdrawal symptoms. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to doxylamine or any inactive ingredients","Concurrent use with monoamine oxidase inhibitors (MAOIs)"]
| Precautions | ["CNS depressant effects; may impair daytime alertness","Risk of anaphylaxis and angioedema","Use with caution in patients with hepatic impairment","Avoid alcohol and other CNS depressants","Elderly patients may be more sensitive to anticholinergic effects"] |
Loading safety data…
| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and sedation level; assess fetal heart rate and uterine activity if used near term. No specific fetal monitoring required for short-term use. |
| Fertility Effects | No known adverse effects on fertility; limited data from animal studies do not indicate impairment. |