Altitude Sickness and Diamox (Acetazolamide)
From Dr Fox (doctorfox.co.uk)
● Most trekkers and climbers do not need, and should not take, Diamox (acetzolamide)
● Altitude problems are unlikely below 2,500 metres (8,000 feet).
● Anybody can suffer from illness caused by altitude. Nobody is immune to it.
● The way to reduce the risk is to acclimatise and be prepared to descend.
Ascend slowly with overnight stops at regular intervals.
● People planning to ascend over 3,000 metres (10,000 feet) should spend a night at an
intermediate elevation below 3,000 metres before they start to ascend.
● Above 3,000 metres ascend only 300-500 metres (1,000-1,500 feet) a day to each next
new sleep height.
● If more than 500 metres (1,500 feet) of ascent is required in the day, descend back to
500 metres to sleep (climb high, sleep low).
● For every 1,000 metres of ascent stop for 2 nights sleep before going higher.
Symptoms of mild early acute mountain sickness
Stop ascending until feeling better.
● Headache not relieved by paracetamol and drinking a litre of water (early symptom of
acute mountain sickness)
● Fatigue and weakness
● Dizziness and light-headedness
● Difficulty sleeping
Do not ascend if these symptoms develop. Stop until the symptoms resolve (usually 24-48 hrs)
or descend. Descending will usually make the symptoms go more quickly.
Ascent can be continued when these symptoms subside, usually after 24-48 hrs.
● Do not keep ascending
● It helps to drink plenty
● Avoid alcohol and sedatives
Emergencies requiring immediate descent
Two sets of symptoms requiring immediate descent:
1. Fluid on the lungs
Showing up as struggling to breath, extreme fatigue, rattling breathing, coughing, blue or grey
lips and fingernails, drowsiness, collapse, confusion and death. This condition is known as HAPE
(High Altitude Pulmonary Oedema). The cardinal feature is extreme shortness of breath -
being short of breath when everybody else has got their breath back.
2. Fluid on the brain
Showing up as changes in behaviour, lethargy, and loss of coordination (unable to walk in a
straight line). This can progress to coma and death. This condition is known as HACE (High
Altitude Cerebral Oedema). The cardinal feature is cognitive impairment (inability to think
straight and carry out normal tasks).
These two conditions are emergencies requiring immediate descent, even if this is in the night.
The descent needs to be at least 500-1,000 metres (1,500-3,000 feet) and as soon as is possible.
Delay can be fatal.
In addition to descent, treatment includes oxygen, steroids and hyperbarric oxygen (oxygen
delivered in a high pressure chamber).
Notes about HACE and HAPE
Can come without any warning
Can develop rapidly over a period of hours
Often start at night, although they can come on in the day
There may be no preceding symptoms or warning
Can affect people who have ascended previously to the same height without problems
Can affect people who have followed the guidelines for acclimatisation
Can affect people who are taking Diamox (acetazolamide)
Can affect fit and unfit people and indigenous people including porters
About Acetazolamide (Diamox)
Diamox increases the amount of urine produced and changes the acidity of the blood. The net effect is
to improve breathing and reduce fluid around the brain and in the lungs.
Acetazolamide is not licensed to prevent and treat altitude sickness although it has long been used for
Diamox side effects
Most people taking acetazolamide for short courses experiences no side effects.
Side effects reported include: a ‘tingling’ feeling in the fingers and toes, some loss of appetite, taste
disturbance, flushing, thirst, headache, dizziness, fatigue, irritability, and depression.
Uses of Acetazolamide (Diamox)
1. In the mild acute mountain sickness (headache, fatigue, light headedness, difficulty with sleep)
symptoms resolve more quickly with Diamox (acetazolamide). The symptoms usually go by themselves
in around 24-48 hrs. This usually reduces to around 12-24 hrs with Diamox.
2. Taking Diamox will reduce the likelihood of altitude sickness in people who are forced to ascend
without proper acclimatisation. Serious illness and even death are still possible. Diamox is not a
substitute for acclimatisation.
3. Diamox improves the pattern of breathing during sleep at altitude and thus quality of sleep. During
sleep at altitude the breathing pattern alters; rapid breaths are followed by prolonged pauses. This is
not dangerous but tends to lead to poor sleep.
We do not recommend taking acetazolamide for people planning to undertake routine ascents. Most
people who acclimatise properly do not need it. Taking Diamox (acetazolamide) can give a false sense of
1. For the treatment of mild early acute mountain sickness (headache, fatigue, light headedness,
difficulty with sleep): Diamox 250mg (one tablet) twice daily until symptoms resolve, when planned
ascent can be resumed.
2. Where rapid ascent without proper acclimatisation cannot be avoided: Diamox 250mg (one tablet)
twice daily. Continue for 2-3 days after final altitude is reached.
3. For disturbed breathing pattern during sleep: Diamox 125mg (half a tablet) twice daily. Continue
until descent to an altitude where sleep is no longer a problem. Acetazolamide is not a sedative.
Stopping Diamox does not cause a rebound in symptoms. The symptoms will not be worse than they
would have been if Diamox (acetazolamide) had not been taken in the first place.
Taking Diamox (acetazolamide) for early symptoms does not mean it is OK to keep ascending. Do not
ascend until symptoms resolve completely, usually 24-48 hrs.
Diamox (acetazolamide) does not mask serious underlying symptoms. It treats the cause not the
symptoms. If a person feels better on Diamox (acetazolamide) it is because their condition has got
Treat altitude with respect. Do not imagine that a strong person can simply battle through. People who
climb and hike in high places have a reputation for pushing themselves. When it comes to altitude;
planning ahead, taking one’s time and responding to one’s own body are virtues.
Dr Fox (doctorfox.co.uk)
Acetazolamide: Patient information
• You should not drive or operate machinery if you feel sleepy or feel your vision is
disturbed after taking this medicine.
Type of medicineCarbonic anhydrase inhibitor
Acetazolamide works by stopping the action of a chemical in the body called carbonic
anhydrase. This reduces the amount of a substance called bicarbonate which is
responsible for high pressure in the eye.
Before taking acetazolamide
Before taking acetazolamide make sure your doctor or pharmacist knows:
• If you are pregnant, trying for a baby or breast-feeding.
• If you are allergic to drugs known as carbonic anhydrase inhibitors, sulfonamides
or thiazide diuretics.
• If you have low potassium or sodium in your blood.
• If you have liver or kidney problems.
• If you have a type of glaucoma called chronic, non-congestive angle-closure
• If you suffer from diabetes mellitus.
• If you have problems with your lungs.
• If you suffer from gout.
• If you suffer from Addison’s disease.
How to take acetazolamide
• The dose will vary depending on what you are being treated for.
• Take exactly as directed by your doctor.
Getting the most from your treatment
• You should keep your appointments with your doctor- s/he will want to monitor
your progress and may take blood tests from time to time.
• You should not drive or operate machinery if you feel sleepy or if your vision is
disturbed after taking this medicine.
Can acetazolamide cause problems?
Along with their useful effects all medicines can cause unwanted side effects, which
usually improve as your body adjusts to the new medicine. Speak with your doctor or
pharmacist if any of the following side effects continue or become troublesome.
Common side-effects – these
affect less than 1 in 10 people What can I do if I experience this
who take this medicine
Eat little and often.
Stick to simple foods such as dry toast.
If you are sick, drink plenty of water.
Drink plenty of water to replace lost fluids.
Ask your pharmacist to recommend a suitable pain-
Speak to your doctor if you notice any unusual skin
Make sure your reactions are normal before driving,
operating machinery or doing any other jobs which
could be dangerous if you were not fully alert.
Myopia (far-away objects appear
Speak to your doctor.
How to store acetazolamide
• Keep all medicines out of the reach of children.
• Store in a cool, dry place, away from direct heat and light.
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