How quickly does Effexor (venlafaxine) work for hot flashes?

Effexor (Venlafaxine) for Hot Flashes: Onset of Action

Venlafaxine begins working for hot flashes within 1-2 weeks, with significant effects seen after 4 weeks of treatment, reducing hot flash frequency and severity by 37-61% depending on dosage. 1, 2

Efficacy Timeline and Dosing

• First week: Initial effects may begin (starting at 37.5mg daily)
• By week 4: Full therapeutic effect established
  • 37.5mg daily: 37% reduction in hot flashes 2
  • 75mg daily: 61% reduction in hot flashes 2
  • 150mg daily: 61% reduction in hot flashes (no additional benefit over 75mg) 2

The optimal dose appears to be 75mg daily, as higher doses (150mg) don't provide additional benefit but may increase side effects 1.

Administration Protocol

1. Starting dose: 37.5mg daily for 7 days
2. Maintenance dose: Increase to 75mg daily if needed 3
3. Duration: The optimal treatment duration is unknown, but efficacy has been demonstrated in studies lasting 4-12 weeks 1
4. Discontinuation: Gradual tapering is recommended to prevent discontinuation symptoms 1

Comparative Efficacy

Venlafaxine has been shown to be:

• More effective than clonidine for hot flashes in breast cancer patients 4
• Preferred by patients over gabapentin (68% vs 32%) despite similar efficacy in reducing hot flashes 3
• Less effective than estrogen therapy, though still clinically significant 1

Side Effects to Monitor

• Common: Dry mouth, decreased appetite, nausea, constipation 2
• Less common: Headache, insomnia, somnolence, dizziness 5
• Note: Side effects are dose-dependent and generally mild to moderate 1

Important Considerations

• Response variability: There is marked variability in individual response, with some women experiencing significant improvement while others may have minimal benefit or even worsening of symptoms 1
• Discontinuation: When stopping venlafaxine, gradual tapering is essential to prevent withdrawal symptoms due to its short half-life 1
• Drug interactions: For patients taking tamoxifen, venlafaxine has less potential to interfere with tamoxifen metabolism compared to some other antidepressants 1

Venlafaxine represents an effective non-hormonal option for managing hot flashes, particularly for women who cannot or choose not to use hormone therapy, with relatively rapid onset of action and good tolerability at the recommended doses.