Emerging treatments

Phosphodiesterase-5 inhibitors for HAPE prophylaxis

Orally administered phosphodiesterase-5 inhibitors (e.g., sildenafil, tadalafil) have been shown to improve oxygenation and exercise capacity in well-acclimatised individuals exposed to hypoxia.[95] This has been thought to be due to an increase in the availability of nitric oxide, a powerful vacillator present in the lungs that is capable of reducing pulmonary artery pressure and improving gas exchange.[95][96]​​ Sildenafil has been used safely in the treatment of HAPE; however, clinical trials into its use have not yet been performed.[57] Nifedipine remains the preferred agent for the prophylaxis of HAPE. However, sildenafil and tadalafil are recommended as alternative options within recent clinical practice guidance.[1]​[26]​

Dexamethasone for HAPE prophylaxis

Dexamethasone is believed to act in a similar way to the phosphodiesterase-5 inhibitors by stimulating alveolar fluid re-absorption and reducing hypoxic pulmonary vasoconstriction. A course of dexamethasone resulted in 0 out of 10 HAPE-susceptible mountaineers developing the condition on arrival at 4559 m compared with 7 out of 9 taking placebo.[97] Until further evidence and experience with dexamethasone is obtained, nifedipine will remain the preferred agent for the prophylaxis of HAPE. 

Ginkgo biloba for acute mountain sickness (AMS) prophylaxis

Ginkgo biloba has been shown in some studies to reduce the incidence and severity of AMS, but other studies have shown no effect.[44][98]​​​ The discrepancy may be due to differences in the source and composition of ginkgo used. Acetazolamide and dexamethasone have been found to be considerably more effective.[7][26]​​

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