Altitude illness medications are some of the most commonly misunderstood and misused medications in mountaineering. I've seen climbers take Diamox incorrectly (wrong dose, wrong timing, for the wrong indication), I've seen climbers refuse medications that could have prevented serious illness, and I've seen climbers take dexamethasone — a serious steroid with significant side effects — for mild symptoms that didn't warrant it. This article is not a substitute for medical consultation, but it provides the practical information you need to use these medications correctly if you've obtained them appropriately through a physician.
Acetazolamide (Diamox)
Acetazolamide (Diamox) is the most widely used altitude medication, effective for prevention and treatment of Acute Mountain Sickness (AMS). It works by increasing respiratory drive, which improves oxygen saturation at altitude. The standard prophylactic dose is 125mg twice daily (half the original dose of 250mg, which was found to be unnecessarily high).
Timing: Start acetazolamide 24 hours before ascent above 3,000m and continue for 48 hours after reaching altitude or until descent begins. Some clinicians recommend starting the evening before ascent. The medication is NOT a substitute for proper acclimatization — it supports the acclimatization process rather than replacing it.
Side effects: The most common side effects are increased urination (you'll pee more frequently), paresthesias (tingling in fingers and toes, which is harmless), and altered taste of carbonated beverages (they taste flat). Less common side effects include nausea, drowsiness, and rare allergic reactions (sulfonamide allergy is a contraindication — if you're allergic to sulfa drugs, you cannot take acetazolamide).
For AMS treatment: 250mg every 12 hours is effective. Combined with rest and descent if symptoms don't improve within 24 hours.
Nifedipine (Procardia)
Nifedipine is used for prevention and treatment of High Altitude Pulmonary Edema (HAPE). It works by dilating pulmonary blood vessels, reducing pulmonary artery pressure and improving oxygenation. Unlike acetazolamide, nifedipine is not routinely used prophylactically except in individuals with a history of HAPE who must ascend rapidly.
Prophylactic dose: Extended-release nifedipine 20mg every 12 hours (or 30mg every 12 hours of the extended-release formulation). Begin the day before ascent and continue for 4-5 days at altitude or until descent.
Treatment dose: Same as prophylactic dose, but note that nifedipine is a treatment adjunct, not a primary treatment — descent and oxygen are the primary treatments for HAPE. Nifedipine supports but does not replace these interventions.
Side effects: Headache, flushing, hypotension (low blood pressure), edema (swelling in ankles), and reflex tachycardia (rapid heart rate). These side effects are generally mild and well-tolerated. The medication should be used with caution in people on other blood pressure medications.
Dexamethasone
Dexamethasone is a corticosteroid used for prevention and treatment of High Altitude Cerebral Edema (HACE). It is NOT used prophylactically except in specific circumstances (prior HACE history with unavoidable rapid ascent). Dexamethasone is a serious medication with significant side effects, and its use should be medically supervised.
Treatment dose: For HACE, dexamethasone 4mg every 6 hours (or 8mg initially followed by 4mg every 6 hours) is standard. This dose is continued until descent is completed and symptoms resolve.
Prophylactic dose (rare indications only): 2mg every 6 hours or 4mg every 12 hours for individuals with prior HACE who must ascend rapidly without adequate acclimatization time.
Side effects: Dexamethasone can cause mood changes, insomnia, hyperglycemia (elevated blood sugar, important for diabetics), immunosuppression with prolonged use, and adrenal suppression with extended use. Short-term use (days) for altitude illness is generally safe, but the side effect profile makes it inappropriate for casual use or mild symptoms.
Other Medications and Treatments
Ibuprofen: 600mg every 8 hours is effective for altitude headache and mild AMS symptoms. It has a better side-effect profile than dexamethasone and is appropriate for symptom management. Not preventive for AMS but effective for headache.
Sildenafil (Viagra) and tadalafil (Cialis): These PDE-5 inhibitors have been studied for HAPE prevention in susceptible individuals and for improving exercise performance at altitude. They work by dilating pulmonary vessels. Standard doses (sildenafil 50mg every 8 hours; tadalafil 10mg every 12 hours) have shown prophylactic benefit. However, they are not standard clinical practice for most climbers and should be reserved for high-risk situations with medical supervision.
Contraindications and Interactions
Acetazolamide is contraindicated in: sulfa allergy, severe kidney disease, liver disease, and adrenal insufficiency. Nifedipine is contraindicated in: severe hypotension, aortic stenosis, and unstable angina. Dexamethasone is contraindicated in: systemic fungal infections and uncontrolled diabetes.
All three medications interact with other drugs. Provide your prescribing physician with a complete list of all medications (prescription, OTC, and supplements) you currently take. This is especially important for diabetics (medications interact with blood sugar control), people on blood pressure medications (additive hypotension risk), and people taking antidepressants or psychiatric medications.
Related Articles
- Altitude Sickness Complete Guide — Full coverage of AMS, HACE, and HAPE
- First Aid for Climbers — Field treatment protocols for altitude illness
- Acclimatization Science — Non-pharmacological prevention strategies