Altitude sickness — acute mountain sickness (AMS) — is a potentially life-threatening condition that affects travellers ascending above approximately 2,500 metres (8,200 feet). With adventure travel and high-altitude trekking increasingly popular among UK holidaymakers, community pharmacists are encountering more pre-travel questions about prevention, the role of acetazolamide, and what symptoms to watch for. Pharmacists with travel health knowledge can provide genuinely valuable — and potentially life-saving — advice.

Who Is at Risk?

Anyone ascending above 2,500 metres is at risk of altitude sickness, regardless of age, fitness or previous altitude experience. According to TravelHealthPro, approximately 25% of travellers sleeping above 3,500 metres experience symptoms of AMS. Common UK traveller destinations where altitude sickness is a concern include:

Key point: physical fitness does not protect against altitude sickness. In fact, fit individuals sometimes ascend faster than their acclimatisation allows, increasing their risk. Previous altitude experience without symptoms does not guarantee immunity on future trips.

Symptoms of Acute Mountain Sickness

AMS typically develops 6–12 hours after arriving at altitude and shares features with a hangover:

• Headache (the cardinal symptom — present in almost all cases)
• Nausea or vomiting
• Fatigue and weakness
• Dizziness or light-headedness
• Difficulty sleeping
• Loss of appetite

Mild AMS is common and usually resolves with rest and acclimatisation. However, it can progress to two life-threatening conditions:

High-altitude pulmonary oedema (HAPE): fluid in the lungs — breathlessness at rest, persistent cough (may produce pink frothy sputum), chest tightness, cyanosis. Fatal without descent and treatment.

High-altitude cerebral oedema (HACE): brain swelling — confusion, ataxia (staggering gait), drowsiness progressing to coma. Fatal without immediate descent.

Acetazolamide: The Pharmacist's Role

Acetazolamide (Diamox) is the only medicine with strong evidence for preventing AMS. It is a carbonic anhydrase inhibitor that works by stimulating ventilation and accelerating acclimatisation.

Key facts for pharmacists

• Classification: Prescription-only medicine (POM) in the UK
• Prophylactic dose: 125 mg twice daily, starting 1–2 days before ascent and continuing for 2–3 days after reaching maximum altitude
• Treatment dose: 250 mg twice daily
• Common side effects: tingling in fingers, toes and lips (paraesthesia); increased urination; altered taste of carbonated drinks; mild nausea. These are predictable and usually well tolerated
• Contraindications: sulphonamide allergy (acetazolamide is a sulphonamide derivative), severe hepatic or renal impairment, hyponatraemia, hypokalaemia, adrenocortical insufficiency
• Drug interactions: increases lithium excretion; may potentiate effects of other carbonic anhydrase inhibitors; high-dose aspirin increases acetazolamide toxicity

Pharmacist counselling point: Patients may request acetazolamide without understanding that it is not a substitute for proper acclimatisation. The drug reduces AMS symptoms but does not eliminate the risk of HAPE or HACE if ascent is too rapid. It is an adjunct to — not a replacement for — a sensible ascent profile.

Who should consider acetazolamide?

TravelHealthPro recommends considering prophylactic acetazolamide for:

• Travellers with a history of AMS on previous trips
• Those ascending rapidly (e.g. flying directly to above 3,000 m, as with La Paz or Cusco)
• Those on fixed itineraries with limited flexibility to slow the ascent (e.g. guided Kilimanjaro treks)
• Those ascending above 3,500 m who are concerned about AMS

Patients should be referred to their GP or a travel health clinic for a prescription and pre-travel consultation.

Acclimatisation Advice

The most effective prevention is gradual ascent. Pharmacists can share these TravelHealthPro guidelines:

• Above 3,000 m, increase sleeping altitude by no more than 300–500 metres per day
• Build in rest days — one rest day for every 1,000 m gained
• "Climb high, sleep low" — ascending during the day and descending to sleep at a lower altitude accelerates acclimatisation
• Stay hydrated — dehydration worsens AMS symptoms. Aim for clear, pale urine
• Avoid alcohol for the first 48 hours at altitude — it depresses ventilation and masks AMS symptoms
• Avoid sleeping pills — sedation reduces the ventilatory drive that helps acclimatisation. Acetazolamide can paradoxically improve sleep at altitude without this risk

What Pharmacists Can Supply

While acetazolamide requires a prescription, pharmacists can supply and advise on:

• Paracetamol and ibuprofen — for altitude headache (first-line symptomatic relief)
• Anti-emetics — prochlorperazine (pharmacy supply under certain conditions) for nausea
• Oral rehydration salts — for maintaining hydration, especially if vomiting occurs
• Sunscreen (SPF 50+) — UV radiation increases significantly with altitude (4% per 300 m); snow and ice reflect up to 80% of UV
• Lip balm with SPF — lips are extremely vulnerable at altitude
• Insect repellent — still needed at many trek destinations below the snow line

The Golden Rules

Pharmacists can summarise altitude safety in three rules that travellers should memorise:

1. If you feel unwell at altitude, it is altitude sickness until proven otherwise — do not attribute symptoms to a cold, hangover or tiredness
2. Never ascend further with symptoms of AMS — rest at current altitude until symptoms resolve
3. If symptoms worsen despite rest, descend immediately — descent is the definitive treatment for all forms of altitude illness. Even 500 metres of descent can produce dramatic improvement

For more information on pharmacy travel health services, visit PharmSee's pharmacy finder or search for pharmacy jobs across the UK.

Sources: TravelHealthPro (NaTHNaC), NHS England, British National Formulary, British Mountaineering Council altitude guidelines.