Interventions for preventing high altitude illness: Part 2. Less commonly‐used drugs

Background High altitude illness (HAI) is a term used to describe a group of mainly cerebral and pulmonary syndromes that can occur during travel to elevations above 2500 metres (˜ 8200 feet). Acute mountain sickness (AMS), high altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE) are reported as potential medical problems associated with high altitude ascent. In this second review, in a series of three about preventive strategies for HAI, we assessed the effectiveness of five of the less commonly used classes of pharmacological interventions. Objectives To assess the clinical effectiveness and adverse events of five of the less commonly used pharmacological interventions for preventing acute HAI in participants who are at risk of developing high altitude illness in any setting. Search methods We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, LILACS and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) in May 2017. We adapted the MEDLINE strategy for searching the other databases. We used a combination of thesaurus‐based and free‐text search terms. We scanned the reference lists and citations of included trials and any relevant systematic reviews that we identified for further references to additional trials. Selection criteria We included randomized controlled trials conducted in any setting where one of five classes of drugs was employed to prevent acute HAI: selective 5‐hydroxytryptamine(1) receptor agonists; N‐methyl‐D‐aspartate (NMDA) antagonist; endothelin‐1 antagonist; anticonvulsant drugs; and spironolactone. We included trials involving participants who are at risk of developing high altitude illness (AMS or HACE, or HAPE, or both). We included participants with and without a history of high altitude illness. We applied no age or gender restrictions. We included trials where the relevant medication was administered before the beginning of ascent. We excluded trials using these drugs during ascent or after ascent. Data collection and analysis We used the standard methodological procedures employed by Cochrane. Main results We included eight studies (334 participants, 9 references) in this review. Twelve studies are ongoing and will be considered in future versions of this review as appropriate. We have been unable to obtain full‐text versions of a further 12 studies and have designated them as 'awaiting classification'. Four studies were at a low r