What is Diamox?
Diamox is a medicine used to treat pressure inside the eye (glaucoma) but it’s also prescribed ‘off-label’ to treat altitude sickness. When a medicine is prescribed off-label it means that it’s prescribed in a way that’s different to its licence. For example, Diamox is a licensed medicine for the treatment of glaucoma, but it’s often prescribed ‘off-label’ as a treatment for altitude sickness because research has shown that it works with minimal risk or side-effects.
Off-label prescriptions are completely safe because clinicians will have read information from peer-reviewed publications that support the treatment’s use in this way. There are usually studies and clinical trials to support the use of the medication as an off-label treatment.
How does Diamox work?
The higher you go above sea level, the less oxygen there is in the air. Altitude sickness, also known as acute mountain sickness (AMS), happens when you travel to a higher altitude too quickly and don’t give your body the chance to acclimatise to the ‘thinner’ (less oxygen-rich) air. Symptoms can include breathlessness, headaches and feeling dizzy, and these are caused by insufficient oxygen entering your body. If left untreated, altitude sickness can be very serious and even fatal, but treatments like Diamox can reduce the risk.
When you take Diamox, its active ingredient causes your body to excrete bicarbonate through your urine. This reduction in bicarbonate changes the pH of your blood, making it more acidic. This increased acidity ‘tricks’ your body into thinking that there are higher levels of carbon dioxide in your blood, and acts to get rid of it through the lungs by causing you to breathe more deeply and quickly. This quicker and deeper breathing increases oxygen circulation throughout your body, lessening the symptoms of altitude sickness.
What doses of Diamox are there?
Diamox is available in a single 250mg dose. It is usually taken one or two days before you plan to ascend to a higher altitude. Taking it before you ascend gives you the chance to adjust to any of the side effects that it may trigger, and also helps to increase the oxygen levels in your body before you experience the thinner air found at higher levels of altitude.
If you are climbing a mountain with an altitude of over 2,500m you should take Diamox before each increase in altitude over 500m.