Is it safe to use Viagra (sildenafil) at high altitudes if I'm at risk for altitude sickness?

Viagra (Sildenafil) for Altitude Sickness Prevention

Sildenafil can be used as a preventive medication for altitude sickness in individuals at risk, as it reduces altitude-induced pulmonary hypertension, though it should be used with caution due to potential side effects including severe acute mountain sickness in some individuals. 1

Mechanism and Effectiveness

Sildenafil works as a phosphodiesterase type-5 (PDE-5) inhibitor that can help prevent high-altitude pulmonary edema (HAPE) by:

• Reducing hypoxic pulmonary vasoconstriction
• Decreasing pulmonary artery systolic pressure
• Improving pulmonary circulation at high altitudes

Research has shown that sildenafil significantly reduces pulmonary artery systolic pressure at rest when used for short-term treatment (1-2 days) at high altitude (MD -4.53; 95% CI -6.72, -2.34; p<0.0001) 2. A randomized, double-blind, placebo-controlled study demonstrated that sildenafil normalized systolic pulmonary artery pressure at high altitude while it remained elevated in the placebo group 3.

Safety Considerations

While sildenafil can be effective, there are important safety considerations:

• Risk of severe acute mountain sickness: Tadalafil (another PDE-5 inhibitor similar to sildenafil) has been associated with severe acute mountain sickness in some individuals 1, 4
• Limited effect on oxygen saturation: Short-term treatment with sildenafil does not significantly improve oxygen saturation after exposure to high altitude 2
• No significant improvement in AMS score: Sildenafil does not appear to improve acute mountain sickness symptoms 2

Recommended Prevention Strategy

For individuals at risk of altitude sickness, a hierarchical approach is recommended:

1. First-line prevention: Slow ascent is the most effective preventive measure

   • Maximum rate of ascent above 2500m should be 300-600 m/day 1
   • Consider rest days for every 600-1200m gained 1

2. Pharmacological prevention options (if slow ascent is not possible):

   • Nifedipine: Recommended for patients with a history of HAPE 1, 5
   • PDE-5 inhibitors (sildenafil/tadalafil): Alternative options 1, 5
   • Dexamethasone: Particularly for short stays less than 5 days 5

Dosing and Administration

If using sildenafil for HAPE prevention:

• Start medication with the ascent
• Continue for 3-4 days after arrival at the terminal altitude
• Typical research dosing: 40mg three times daily 3

Important Caveats

• Immediate treatment for HAPE: If symptoms develop despite prevention, immediate descent to lower altitude and supplemental oxygen are the primary therapies 1
• Individual susceptibility: Personal history of HAPE is the most important risk factor 5
• Combination therapy: Some evidence suggests combining tadalafil with acetazolamide may be more effective than acetazolamide alone (4% vs 26% severe high-altitude illness) 6

For individuals with cardiovascular conditions, additional caution is warranted as high altitude exposure increases both pulmonary and systemic blood pressure, which may exacerbate underlying conditions 1.