Acetazolamide is a type of diuretic (‘water pill’) known as a carbonic anhydrase inhibitor. It is used to treat certain types of seizures, glaucoma and limit the build-up of body fluids caused by congestive heart failure. It is also commonly used to manage altitude sickness by decreasing headaches, tiredness, nausea, dizziness and shortness of breath, which occur when climbing to high altitudes - usually above 2,500 metres.
Acetazolamide can help you adjust to high altitudes and prevent altitude sickness symptoms. You can take acetazolamide if you are planning to walk or climb to high altitudes. You should start taking acetazolamide one or two days before you begin to ascend to high altitudes and follow standard precautions. Acetazolamide can be used to reduce the symptoms of altitude sickness, but will not completely cure them. If you are already taking acetazolamide and begin to experience altitude sickness, you must stop your ascent or descend by at least 500m.
Acetazolamide is not an immediate cure for altitude sickness - it speeds up acclimatisation and reduces symptoms. It causes the kidneys to excrete bicarbonate, causing the blood to become more acidic. This rise in blood acidity tricks the body into thinking it has an excess of carbon dioxide, which it seeks to excrete through deeper and more regular breathing. In doing so, the body increases the amount of oxygen in the blood, which helps reduce the symptoms of altitude sickness.
You can take acetazolamide to prevent altitude sickness rather than treat it. Start taking acetazolamide one or two days before you begin your ascent to altitudes of 2,500m and above to allow your body to get used to acetazolamide and adjust accordingly. You should continue to take acetazolamide as you ascend and 24 hours after remaining at a constant altitude.
It is unknown if acetazolamide is effective in treating the symptoms of altitude sickness after they occur. Using acetazolamide as treatment can take up to 48 hours to take effect, by which time your body may well have adjusted on its own.
1 or 2 tablets, once daily
|Type of Medicine||
Carbonic anhydrase inhibitor
Inhibits the absorption of bicarbonate, increasing oxygen content in the blood
28, 56 or 112 tablets
From 89p per tablet
Can include headache, nausea, vomiting, loss of appetite, diarrhoea, metallic taste in the mouth, dizziness, depression, confusion
The active ingredient is acetazolamide. Each tablet contains a 250mg dose of acetazolamide.
The inactive ingredients in acetazolamide 250mg tablets are dicalcium phosphate, corn starch, magnesium stearate, sodium starch glycolate and povidone.
Please note: inactive ingredients may vary between different brands of generic medication. Please read the patient information leaflet for further information.
One tablet contains 250 mg of acetazolamide. For rapid ascension to high altitude, take one tablet twice daily, beginning one or two days before starting your ascent. If taking this medication to relieve symptoms of altitude sickness, take half a tablet twice daily.
Take acetazolamide as instructed by your doctor. Long-acting tablets (250 mg) should be taken twice daily, beginning at least 24 hours before ascending to high altitudes (2,500m and above). These tablets are designed for extended-release, so you mustn’t chew or crush them, but swallow them whole with a drink of water.
Acetazolamide tablets for altitude sickness should not be crushed or chewed. Tablets are designed to work over several hours and should be swallowed whole with a drink of water.
Some people may experience mild side effects when taking acetazolamide, including:
Less common side effects include:
Like all medicine, acetazolamide can cause severe allergic reactions, although this is very rare. You should seek emergency medical help immediately if you experience any sudden wheezing, difficulty breathing, swelling of the eyelids, face or lips, rash or itching.
In rare cases, acetazolamide can affect blood cells, increasing your chance of catching infections and affecting your blood’s ability to clot properly. Contact your doctor immediately if you have a sore throat or fever, or notice bruises or tiny red spots on your skin whilst taking this medication. If your muscles feel weak, or you have seizures, seek urgent medical attention.
Acetazolamide can also very rarely affect the liver and kidneys. You should contact a doctor if you experience pain in your lower back, pain or difficulty passing urine, inability to pass urine, blood in your urine, pale stools, or yellowing of your skin or the whites of your eyes.
You should not take acetazolamide tablets if:
You should let your doctor know if you are taking other medicines or plan to take other medicines whilst taking acetazolamide. The effects of the following medicines, in particular, may be altered by taking acetazolamide:
Avoid drinking alcohol when taking acetazolamide as the combination increases the risk of experiencing drowsiness. If taking acetazolamide for altitude sickness, alcohol should be avoided at all costs, as the dehydrating effect of alcohol can make the symptoms of altitude sickness worse.
When travelling to altitudes above 2,500 metres, the best way to acclimate yourself and avoid altitude sickness is to make your ascent slowly. It usually takes your body a few days to get used to a change in altitude, so you should take two to three days to rest and adapt before ascending further than 2,500m. Take the following precautions as you climb to higher altitudes:
Altitude sickness symptoms can include headaches, nausea and vomiting, dizziness, tiredness, loss of appetite, and shortness of breath. These symptoms commonly worsen during night-time. If you think you have symptoms of altitude sickness, the following advice may help:
Diamox is a brand name for acetazolamide, which is the generic name for the drug. As of April 2015, it is no longer possible to buy Diamox in the UK. The treatment is now sold generically as ‘acetazolamide’ and contains the same dosage and ingredients as the original Diamox.
There are measures for managing altitude sickness, which you should follow regardless of whether you have chosen to take acetazolamide. acetazolamide is designed to reduce the severity of your symptoms rather than prevent or cure them altogether. Taking the following precautions can be equally as effective in preventing altitude sickness:
If you begin to experience symptoms of altitude sickness, see the following measures:
You cannot buy acetazolamide over the counter at a pharmacy. It must be prescribed by a travel doctor, GP or online pharmacy. Although it is not currently licensed in the UK as a treatment for altitude sickness, it can be legally prescribed for this purpose.
Those who suffer from migraines triggered by travelling to high altitudes may find that taking acetazolamide two to three days before their trip prevents migraines from occurring. However, there is little evidence suggesting that taking acetazolamide is beneficial to those who suffer from migraines unrelated to altitude changes.
Ménière’s disease is characterised by vertigo, a ringing sound in the inner ear, a feeling of pressure deep inside the ear and a sudden loss of hearing. While the exact cause of Ménière’s disease is unknown, it is associated with an increase in pressure inside the inner ear.
The most common treatments recommended by GPs are prochlorperazine, which helps relieve severe nausea and vomiting, and antihistamines, which help relieve mild nausea, vomiting and vertigo. However, diuretics such as acetazolamide can treat Ménière’s disease, relieving the inner ear fluid build-up and reducing vertigo and hearing loss.
There is some evidence to suggest that acetazolamide can help lower blood pressure. Through encouraging the body to increase its oxygen intake, acetazolamide helps reduce the rise in blood pressure associated with an increase in altitude.
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