Diamox (Acetazolamide)

What is Diamox?

Diamox is the brand name for Acetazolamide, a carbonic anhydrase inhibitor that has been used in clinical medicine since the 1950s. In the context of travel health, Diamox is the best-evidenced pharmacological option for the prevention and treatment of acute mountain sickness (AMS) — an illness that can affect travellers, trekkers, and climbers who ascend rapidly to high altitudes.

Acute mountain sickness is caused by the physiological stress of reduced atmospheric oxygen pressure (hypoxia) at altitude. Symptoms typically begin within hours of arriving at high altitude and can include headache, nausea, dizziness, fatigue, and difficulty sleeping. AMS can progress to life-threatening high-altitude cerebral oedema (HACE). High-altitude pulmonary oedema (HAPE) is a distinct altitude illness that can occur with or without AMS.

How does Diamox work?

Diamox inhibits the enzyme carbonic anhydrase, which plays a key role in acid-base regulation in the body. By inhibiting this enzyme, Diamox causes the kidneys to excrete bicarbonate into the urine, producing a mild metabolic acidosis (a slight decrease in blood pH).

This mild acidosis stimulates breathing — specifically, it increases ventilatory rate and depth. More frequent and deeper breathing raises blood oxygen saturation, which is the primary mechanism by which Diamox prevents and treats altitude sickness. In effect, Diamox helps the body adapt (acclimatise) to altitude more rapidly than it would otherwise.

The diuretic effect of Diamox (increased urine production) is a side effect of this mechanism rather than the primary therapeutic action.

Who is Diamox for?

Diamox may be appropriate for travellers who:

• Plan to ascend to altitudes above 2,500–3,000 metres, particularly if rapid ascent is planned
• Have a history of previous altitude sickness
• Cannot follow a gradual ascent schedule due to time constraints (e.g., flying directly to a high-altitude destination)
• Are considering high-altitude trekking in regions such as Nepal, the Andes, Kilimanjaro, or high-altitude parts of the Tibetan Plateau

Diamox is not a substitute for gradual acclimatisation. Travel guidance prioritises gradual ascent: above 3,000 metres, limit the increase in sleeping altitude to no more than 500 metres per day and include rest days. Diamox is a complement to, not a replacement for, sensible ascent planning.

The Spanish Edemox contraindications are listed in the safety section below. Its 250 mg tablet score is not intended to divide the tablet into equal doses, and its authorised indications do not include altitude illness. Guideline use for altitude does not establish Spanish licensing or a particular available formulation.

Dosage

The following adult prevention doses describe WMS 2024 guidance, not a Spanish licensed altitude regimen:

If descending immediately after reaching the target altitude, WMS allows stopping when descent starts. There is no routine taper in this guidance. The doctor must select the formulation and dose; do not assume half an Edemox tablet provides 125 mg.

Acetazolamide can be used for established AMS under medical direction. For HACE, it is only an adjunct to dexamethasone; it is not a treatment for HAPE. Severe or worsening symptoms require urgent assessment and descent, with oxygen where available.

Side effects

Effects of its pharmacological action

• Increased urination: Diamox is a mild diuretic. Adequate hydration is important.
• Paraesthesia: Tingling or numbness in the fingers, toes, and around the mouth. This can be uncomfortable; report persistent or concerning symptoms.
• Altered taste of carbonated drinks: Fizzy drinks may taste flat or unpleasant.
• Fatigue: Some patients report mild tiredness.
• Nausea: Particularly at higher doses.

Other side effects

• Reduced appetite
• Headache (may overlap with altitude sickness symptoms)
• Blurred vision
• Rash

Serious side effects

• Severe allergic reactions (including Stevens-Johnson syndrome): Patients with sulfonamide hypersensitivity are at higher risk.
• Haematological changes: Including aplastic anaemia and thrombocytopenia.
• Electrolyte disturbances: Particularly low potassium (hypokalaemia) with prolonged use.

Diamox vs alternative altitude sickness strategies

Online assessment for Diamox (Acetazolamide)

Prescrivia is a technology intermediary connecting patients with independent doctors and licensed pharmacies. We do not provide medical services, prescribe, employ doctors, sell or dispense medicines.

1. Assessment: Provide your symptoms or travel plans, medical history and all current medicines.
2. Independent review: A doctor decides whether a prescription is clinically appropriate; Prescrivia does not guarantee a prescription.
3. Dispensing: Any lawful dispensing is the responsibility of a licensed pharmacy, subject to the applicable rules and product availability.

In Spain, distance selling of prescription medicines is prohibited. An online assessment or a product label does not establish that a medicine can legally be supplied or delivered through this platform. This information does not change eligibility or fulfilment rules.

Important safety information

Do not take acetazolamide under the Spanish Edemox label if you:

• Have a known allergy to sulfonamides, sulfa drugs, acetazolamide or its excipients
• Have severe liver or kidney disease, or cirrhosis
• Have Addison’s disease or adrenal insufficiency
• Have low blood sodium or potassium (hyponatraemia or hypokalaemia)
• Have hyperchloraemic acidosis
• Are in the first trimester of pregnancy
• Need long-term use for chronic non-congestive angle-closure glaucoma
• Have previously experienced non-cardiogenic pulmonary oedema after taking acetazolamide

Tell your doctor if you:

• Have kidney stones (Diamox increases the risk)
• Are taking other diuretics, aspirin, or lithium
• Have diabetes (Diamox may affect blood glucose)
• Are breastfeeding

The Edemox label recommends blood counts and electrolyte monitoring before and regularly during treatment. New severe rash or blood disorders require stopping and medical assessment. A confirmed acute generalised exanthematous pustulosis reaction means acetazolamide must not be restarted.

Acetazolamide-related pulmonary oedema: Severe non-cardiogenic pulmonary oedema has occurred after acetazolamide, even after a single dose, usually within minutes to hours. Symptoms include difficulty breathing, low blood oxygen and respiratory failure. If this reaction is suspected, stop acetazolamide and seek urgent medical attention for supportive treatment. This drug reaction is distinct from high-altitude pulmonary oedema (HAPE); do not assume new breathing symptoms are only due to altitude.

Descent is essential in severe or worsening illness: If symptoms of altitude sickness are severe or worsening, the most important action is immediate descent to a lower altitude. Diamox is an adjunct, not a substitute for descent in serious cases.

Sources

• AEMPS: Edemox 250 mg, product information
• Wilderness Medical Society: 2024 altitude guideline summary and dosing table
• CDC Yellow Book: High-altitude travel and altitude illness
• BOE: Real Decreto Legislativo 1/2015, article 3.5

This is general information, not individual prescribing advice. A clinician must reconcile guideline use with the actual product’s contraindications and your ascent plan.