Diamox (acetazolamide) tablets contain the active ingredient acetazolamide, which is a type of medicine called a carbonic anhydrase inhibitor. Acetazolamide has a number of uses including its use in altitude sickness, although this indication is off label/not approved. Despite this it is the most tried and tested drug for altitude sickness prevention and treatment. It can decrease headache, tiredness, nausea, dizziness and shortness of breath that can occur if climbing quickly to high altitudes (generally above 10,000 feet/3,048 meters). It is particularly useful in situations when a slow ascent is not possible.
Acetazolamide works in the kidneys, where it increases the amount of bicarbonate that passes into the urine. Bicarbonate draws water along with it from the kidneys into the urine. This results in a small increase in the amount of water being lost from the body, a process known as diuresis. Acetazolamide causes only minor water loss, as it is a weak diuretic.
By removing bicarbonate the blood is re-acidified, balancing the effects of the hyperventilation that occurs at altitude in an attempt to get oxygen. This re-acidification acts as a respiratory stimulant, particularly at night, reducing or eliminating the periodic breathing pattern common at altitude. Its net effect is to accelerate acclimatization. Acetazolamide isn't a magic bullet, cure of altitude sickness is not immediate. It makes a process that might normally take about 24-48 hours speed up to about 12-24 hours.
However by far the best way to prevent altitude sickness is by climbing slowly, stopping for 24 hours during the climb to allow the body to adjust to the new height, and taking it easy during the first few days.
For prevention of altitude sickness, the dose is one azithromycin 250mg capsule to be taken twice a day. It should be started one or two days before commencing ascent and continued for three days after the highest altitude is reached. You start taking azithromycin before ascent as the blood concentrations of acetazolamide peak between one to four hours after administration of the tablets.
For treatment of altitude sickness, the dose is one azithromycin 250mg capsule to be taken twice a day for three days then stop.
Dizziness, lightheadedness, and an increased amount of urine may occur, especially during the first few days as your body adjusts to the medication. Blurred vision, dry mouth, drowsiness, loss of appetite, stomach upset, headache and tiredness may also occur. If any of these symptoms persist or worsen, notify your doctor or pharmacist.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor immediately if any of the following very unlikely but serious side effects occur:
- Increased body hair;
- Hearing loss;
- Ringing in the ears;
- Unusual tiredness;
- Persistent nausea/vomiting;
- Severe stomach/abdominal pain.
Seek immediate medical attention if any of the following unlikely but very serious side effects occur:
- Easy bleeding/bruising;
- Fast/irregular heartbeat;
- Signs of infection (e.g., fever, persistent sore throat);
- Mental/mood changes (e.g., confusion, difficulty concentrating);
- Severe muscle cramps/pain;
- Tingling of the hands/feet;
- Blood in the urine, dark urine, painful urination;
- Yellowing of the eyes/skin.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
Acetazolamide should be used with caution in:
- Elderly people.
- People with breathing difficulties such as emphysema.
- People with decreased kidney or liver function.
- People with a history of kidney stones.
- People who have difficulty passing urine.
- People who have unstable levels of electrolytes (salts such as sodium and potassium) in their blood.
Acetazolamide should not be used in:
- People who are allergic to medicines from the sulphonamide group, eg the antibiotic sulfamethoxazole.
- People with underactive adrenal glands (the glands that produce the body's natural steroid hormones).
- People with low levels of potassium or sodium in their blood (hypokalaemia or hyponatraemia).
- People with high levels of chloride in their blood (hyperchloraemic acidosis).
- Severe kidney disease.
- Severe liver disease.
- Long-term use in a type of glaucoma called chronic non-congestive angle-closure glaucoma.
Acetazolamide should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
If you feel you have experienced an allergic reaction, stop using acetazolamide and inform your doctor or pharmacist immediately.
The patient information leaflet (PIL) is a leaflet containing specific information about medical conditions, doses and side effects. You can download a copy of the PIL here:
Patient Info Leaflet