What is the recommended dosing of doxepin for insomnia?

Doxepin Dosing for Insomnia

The recommended dosage of doxepin for insomnia is 3-6 mg taken 30 minutes before bedtime, with clinical evidence supporting these low doses specifically for sleep maintenance insomnia. 1, 2

Dosing Guidelines

• Standard adult dosing: 3-6 mg once daily at bedtime 1, 2
• Elderly patients: Start at the lower dose (3 mg) due to increased sensitivity to medications and higher risk of adverse effects 2, 3
• Duration of therapy: While the FDA label doesn't specify maximum duration, clinical trials have demonstrated efficacy and safety for up to 12 weeks 4

Mechanism and Efficacy

Doxepin at low doses (3-6 mg) works primarily as a selective histamine H1 receptor antagonist, which is different from its action at higher doses used for depression (75-300 mg) 4:

• Sleep maintenance: Doxepin shows clinically significant improvements in:

  • Wake after sleep onset (WASO) 1, 5
  • Total sleep time (TST) 1, 5
  • Sleep efficiency (SE), particularly in the final third of the night 1, 6

• Sleep onset: Less effective for sleep onset compared to other medications:

  • Produces only a small (22%) improvement in latency to persistent sleep 7
  • Not the first choice for predominant sleep onset insomnia 2

Clinical Considerations

• Indications: Primarily for sleep maintenance insomnia rather than sleep onset difficulties 1, 2

• Advantages over other hypnotics:

  • Not a controlled substance 7
  • Lower risk of dependence and withdrawal symptoms 3, 4
  • May preserve sleep architecture better than some alternatives 6
  • Potentially better for improving executive function compared to zolpidem 5

• Special populations:

  • Elderly: Preferred option due to lower risk of falls and cognitive impairment 2
  • Substance use history: May be preferred as a non-scheduled option 2

Monitoring and Side Effects

• Common side effects: Generally well-tolerated at these low doses 4
• Monitoring: Assess sleep parameters within 2-4 weeks of starting treatment 2
• Caution: At higher doses (not recommended for insomnia), anticholinergic effects may occur including dry mouth, blurred vision, and constipation 3

Common Pitfalls to Avoid

1. Using higher doses: Do not use doses above 6 mg for insomnia. Higher doses (25-300 mg) are for depression and have different side effect profiles 3
2. Expecting immediate sleep onset improvement: Doxepin is more effective for sleep maintenance than sleep onset 1, 7
3. Not considering the elderly: Elderly patients should start at 3 mg due to potential for decreased hepatic/renal function 2, 3
4. Overlooking non-pharmacological approaches: Consider combining with cognitive behavioral therapy for insomnia (CBT-I) for optimal outcomes 2

Doxepin at 3-6 mg represents an evidence-based option specifically for sleep maintenance insomnia with a favorable safety profile compared to many alternatives.