How quickly does Effexor (venlafaxine) work to reduce hot flushes?

Venlafaxine for Hot Flushes: Onset of Action

Venlafaxine typically begins to reduce hot flushes within 1-4 weeks of treatment, with significant effects observed after 4 weeks of consistent use. 1

Efficacy Timeline

• First week: Initial effects may begin for some patients
• 4 weeks: Significant reduction in hot flush frequency (39% reduction) 2
• 8 weeks: Further improvement with 53% reduction in hot flush frequency and 59% reduction in hot flush score (measuring both frequency and severity) 2

Dosing and Efficacy

Venlafaxine is recommended as a first-line pharmacological treatment for hot flushes, with evidence showing:

• Efficacy: 37-61% reduction in hot flush scores compared to placebo 3
• Standard dosing: 75 mg/day is typically recommended for vasomotor symptom management 1
• Low-dose option: Even at 37.5 mg/day, venlafaxine shows effectiveness with minimal side effects 2

Comparative Efficacy

In randomized controlled trials, venlafaxine has demonstrated:

• Significant reduction in hot flush scores after 4 weeks of treatment 4
• Dose-dependent response:
  • 37.5 mg/day: 37% reduction
  • 75 mg/day: 61% reduction
  • 150 mg/day: 61% reduction 4

Important Considerations

• Gradual onset: Unlike hormonal therapies, venlafaxine does not provide immediate relief but builds effectiveness over several weeks
• Discontinuation: Gradual tapering is essential to prevent withdrawal symptoms 1
• Side effects: Most common include headache, dry mouth, nausea, insomnia, somnolence, and dizziness 3
• Follow-up: Reassessment after 4 weeks is recommended to evaluate efficacy and consider dose adjustments if needed 1

Clinical Pearls

• Side effects are typically most pronounced during the first 2 weeks of treatment and often diminish over time 2
• Low-dose venlafaxine (37.5 mg/day) may be sufficient for many patients while minimizing side effects 2
• Venlafaxine is particularly valuable for patients with contraindications to hormone therapy or those concerned about potential risks of estrogen therapy 3

Treatment Algorithm

1. Start with venlafaxine 37.5 mg/day
2. Assess response after 4 weeks
3. If inadequate improvement:
   • Consider increasing to 75 mg/day (offers better efficacy without significantly more side effects than 150 mg/day) 4
   • Reassess after another 4 weeks
4. If still inadequate, consider alternative treatments such as gabapentin or paroxetine 1

Remember that while venlafaxine is effective, patients should be counseled about the gradual onset of action and the importance of consistent use for at least 4-8 weeks to achieve optimal benefits.