Indications for Doxylamine Administration
Doxylamine is primarily indicated for insomnia and nausea/vomiting of pregnancy, with the standard adult dose being one 25mg tablet taken 30 minutes before bedtime for sleep disturbances. 1
Primary Indications
1. Insomnia
- Dosage: 25mg orally once daily, taken 30 minutes before bedtime 1
- Population: Adults and children 12 years and older
- Contraindication: Not recommended for children under 12 years 1
- Mechanism: Acts as an H1-receptor antagonist with sedative properties
- Duration: Indicated for short-term management of occasional insomnia 2
2. Nausea and Vomiting of Pregnancy (NVP)
- First-line pharmacologic therapy for persistent NVP when non-pharmacologic measures fail 3
- Dosage: Available in combination with pyridoxine (vitamin B6) in 10mg/10mg and 20mg/20mg formulations
- Safety: FDA-approved and recommended by the American College of Obstetricians and Gynecologists (ACOG) for NVP 3
- Timing: Used when NVP is refractory to non-pharmacologic therapies such as:
- Dietary modifications (small, frequent meals; BRAT diet)
- Ginger (250mg four times daily)
- Vitamin B6 (10-25mg every 8 hours)
Clinical Considerations
Pharmacokinetics
- Linear and dose-dependent absorption between 12.5mg and 25mg doses 4
- Elderly men (but not women) show reduced clearance and prolonged half-life (15.5h vs 10.2h in younger men) 5
- Intranasal formulations do not provide faster onset or improved bioavailability compared to oral tablets 6
Special Populations
- Elderly: Consider lower doses in elderly men due to reduced clearance 5
- Pregnancy: Safe and well-tolerated for NVP; early intervention may prevent progression to hyperemesis gravidarum 3
Cautions and Adverse Effects
- Common side effects: Sedation, drowsiness, dizziness
- Serious complications: Rare cases of rhabdomyolysis reported with overdose 7
- Administration timing: Evening administration minimizes daytime sedation
- Monitoring: Watch for excessive sedation, especially when combined with other CNS depressants
Clinical Pearls
- Doxylamine may be particularly useful for maintenance insomnia (sleep disturbances in the last third of the night) due to its histamine H1 inverse agonist properties 2
- Early treatment of NVP with doxylamine and pyridoxine combination may prevent progression to more severe hyperemesis gravidarum 3
- For insomnia, doxylamine is available over-the-counter, making it an accessible option for patients
Remember that while doxylamine is effective for short-term management of insomnia, it is not intended for long-term use, and underlying causes of sleep disturbances should be addressed.