Beyond the prescription pill: what the evidence says prevents altitude sickness

Most coverage of altitude-sickness prevention centres on one prescription drug, acetazolamide. But the more practical question for a traveller heading up a mountain is what else works — and here the evidence is unexpectedly clear in two directions. A randomised trial found that ordinary ibuprofen, a cheap over-the-counter anti-inflammatory, meaningfully reduced acute mountain sickness [s1], while a Cochrane review found that most of the supplements and pre-acclimatisation gadgets marketed for the purpose do not stand up [s2].

How common the problem is

Acute mountain sickness (AMS) — the headache, nausea, fatigue and poor sleep that can follow a rapid climb — occurs in more than 25% of the tens of millions of people who travel to high altitude each year [s1]. It is the mild end of a spectrum that runs up to the rare, life-threatening syndromes of high altitude cerebral and pulmonary oedema [s2]. High altitude illness is generally described as occurring during travel to elevations above 2500 m (about 8200 ft) [s2], and the single biggest driver is ascending faster than the body can adjust.

The ibuprofen trial

The randomised trial recruited healthy adults living at low altitude and assigned them to ibuprofen 600 mg or placebo three times daily, starting six hours before an ascent from 1,240 m (4,100 ft) to 3,810 m (12,570 ft) in the White Mountains of California during July and August 2010 [s1]. AMS was scored with the Lake Louise Questionnaire, using a diagnostic threshold of a score of 3 or more with headache plus one other symptom [s1].

Of 86 participants who completed the study — 44 on ibuprofen, 42 on placebo — fewer developed AMS in the ibuprofen group, 43% versus 69% on placebo [s1]. That corresponds to an odds ratio of 0.3 (95% confidence interval 0.1 to 0.8) and a number needed to treat of 3.9 (95% CI 2 to 33) [s1]. Symptom severity was also lower on ibuprofen [s1]. It is a single, modest-sized trial in young, healthy volunteers on one specific ascent profile, so it is a promising signal rather than the last word — but it is genuine randomised evidence for an accessible, non-prescription option.

What does not hold up

The Cochrane review is the useful counterweight to the wellness aisle. It pooled 20 studies with 1,406 participants testing non-pharmacological and miscellaneous strategies [s2]. Pre-acclimatisation using simulated altitude might not reduce AMS risk, and the effect was uncertain (risk ratio 1.18, 95% CI 0.82 to 1.71; three trials, 140 participants; low-quality evidence) [s2]. Supplements fared no better: antioxidants, iron and the herbal remedy Rhodiola crenulata all showed effects too uncertain to recommend [s2]. For ginkgo biloba, the reviewers could not even pool the trials because they disagreed so much, with individual risk ratios ranging from 0.05 to 1.03 [s2].

The overall verdict was that the evidence for these approaches is heterogeneous, sometimes contradictory, and low to very low in quality, with their safety largely unassessed [s2]. In other words, the popular "natural" preventives are not backed by convincing trial data — a null result worth knowing before spending money on them.

Where the guidelines sit

Expert bodies have tried to synthesise all of this. The Wilderness Medical Society convened an expert panel to produce graded, evidence-based clinical practice guidelines for the prevention, diagnosis and treatment of acute mountain sickness and its severe forms, with recommendations rated by the quality of supporting evidence [s3]. Such guidance frames medication and supplements as adjuncts to sensible ascent rather than substitutes for it — the trials above test what to add, not a replacement for giving the body time to adjust.

What it leaves a reader

The evidence supports a clear hierarchy of confidence rather than a shopping list. Rapid ascent above 2500 m is the core risk [s2]; among the add-on options a traveller might reach for, ibuprofen has real randomised support [s1], whereas antioxidants, iron, Rhodiola and ginkgo do not [s2]. None of this is personalised advice: who should take anything, at what dose, and how fast to climb are decisions for a clinician familiar with a given traveller's health and itinerary. Severe or worsening symptoms at altitude — especially confusion, breathlessness at rest or an unsteady gait — are red flags for the dangerous syndromes and a reason to descend and seek care without delay [s2].