Acetazolamide

What is Acetazolamide?

Acetazolamide is a type of diuretic (water pill) known as a carbonic anhydrase inhibitor. It is used for treating certain types of seizures and glaucoma, and limiting the build-up of body fluids caused by congestive heart failure. It is also commonly used to manage altitude sickness by decreasing symptoms such as headaches, tiredness, nausea, dizziness and shortness of breath, which occur upon ascension to high altitudes - usually above 3,000 metres.

How does Acetazolamide work?

Acetazolamide is not an immediate cure for altitude sickness - it speeds up the process of acclimatization 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 CO2, which is 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.   

Who should take Acetazolamide?

Acetazolamide can help you adjust to high altitudes and prevent the symptoms of altitude sickness, and is taken by those who are planning a walk or climb to high altitudes. This medication should be started 1-2 days before you begin to ascend to high altitudes, and normal precautions should be followed. 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, it is important that you stop your ascent or descend by at least 500m.

How long does it take for Acetazolamide to work?

For treatment of altitude sickness, Acetazolamide is usually taken in a preventative capacity. It should be taken between 24 and 48 hours before you begin your ascent to altitudes of 3,00m and above in order to allow the body to register the treatment and adjust accordingly. You should continue to take acetazolamide as you ascend, and for 24 hours after remaining at a constant altitude. 

The true efficiency of Acetazolamide in treating the symptoms of altitude sickness after they occur is unknown. The treatment can take up to 48 hours to take effect, by which time your body may well have adjusted on its own.  

Is Acetazolamide for altitude sickness off-label use?

Acetazolamide was originally licensed for use in the treatment of glaucoma and epilepsy. However, it has also been found to be an effective method to prevent altitude sickness. The original license has not been extended to cover altitude sickness, but this does not mean that it is unsafe or ineffective. It is an expensive process to get a license extended, so manufacturers often avoid doing this. Doctors are able to prescribe medications off-label when there is evidence to suggest that it is the most appropriate treatment available. The NHS has produced a useful document on this subject which you can access here for more information.

How to acclimatise to high altitude

When travelling to altitudes above 3,000 metres, the best way to acclimate yourself and avoid altitude sickness is to make your ascent slowly. It usually takes the body a few days to get used to a change in altitude, so you should take 2-3 days to rest and adapt before ascending further than 3,000m. The following precautions should be taken as you ascent further:

• Avoid climbing more than 300-500m per day.
• Spend a day resting after every 600-900m, or rest every 4-3 days.
• Drink plenty of water.
• Avoid strenuous exercise, particularly in the first 24 hours.
• Try and eat a light but high calorie diet.
• Avoid alcohol or smoking.  

How to relieve symptoms of altitude sickness

Symptoms of altitude sickness can includes headaches, nausea and vomiting, dizziness, tiredness, loss of appetite and shortness of breath. These symptoms commonly worsen at during nighttime. If you think you have symptoms of altitude sickness, the following advice may help:

• Stop and rest.
• Do not ascend further for at least 24-48 hours.
• Make sure you are drinking plenty of water.
• Avoid exercise.
• Avoid smoking or drinking alcohol.
• Take painkillers, such as paracetamol or ibuprofen, to relieve you headache.
• Take anti-sickness medication, such as promethazine, if you feel nauseous. 

Active ingredients

The active ingredient is acetazolamide. Each tablet contains a 250mg dose of acetazolamide.

Inactive ingredients

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. 

Can Acetazolamide be crushed?

Acetazolamide for altitude sickness should not be crushed or chewed. Tablets are designed to work over an extended period of time and should be swallowed whole with a drink of water.

How to take Acetazolamide

Most importantly, take Acetazolamide as instructed by your doctor and according to the packet information. Long-acting tablets (250 mg) should be taken twice daily, beginning at least 24 hours before ascending to high altitudes (3,000m and above). These tablets are designed for extended release, so it is essential that you do not chew or crush them, but swallow them whole with a drink of water.  

Acetazolamide dosage

Once tablet contains 250 mg of acetazolamide. For rapid ascension to high altitude, take one tablet twice daily, beginning 1 or 2 days before you begin your ascent. If taking this medication in relieve symptoms of altitude sickness, take half a tablet twice daily.

Acetazolamide side effects

Some people may experience mild side effects when taking Acetazolamide, including:

• Headaches and dizziness
• Nausea, vomiting, loss of appetite or thirst
• Diarrhoea
• Tiredness or irritability
• Need to pass urine more than usual
• Feeling over-excited and appearing flushed
• Tingling or numbness in fingers or toes, or loss of total control of arms or legs.

Less common side effects include:

• Drowsiness or confusion
• Depression
• Loss of sexual appetite
• Ringing in the ears or difficulty hearing
• Temporary short-sightedness which subsides when the dosage is reduced

Like all medicine, Acetazolamide can cause serious allergic reactions, although this is very rare. You should contact a doctor immediately if you experience any sudden wheezing, difficulty breathing, swelling of the eyelids, face or lips, rash or itching. 

In extremely 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 are having fits, 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.

Contraindications

You should not take Acetazolamide tablets if:

• You are pregnant, think you might be pregnant or are planning on becoming pregnant.
• You are allergic to sulfonamides, sulfonamide derivatives, or any of the listed. medications in acetazolamide 250mg tablets.
• You have severe liver problems.
• You have kidney problems.
• You have chronic non congestive angle closure glaucoma.
• You have reduced function of the adrenal glands (Addison’s disease).
• You have low blood levels of sodium and/or potassium, or high blood levels of chlorine.   

Drug interactions

You should let your doctor know if you are taking other medications or plan to take other medications whilst taking Acetazolamide. The effects of the following medications in particular may be altered by taking Acetazolamide:

• Medicines for the heart, such as cardiac glycosides
• Medicines to reduce blood pressure
• Blood thinning medications
• Medicines to reduce blood-sugar level
• Epilepsy medication
• Medicines which interfere with folic acid
• Steroids
• Aspirin
• Other types of carbonic anhydrase inhibitors
• Amphetamines, quinine, methenamine or lithium
• Sodium bicarbonate therapy
• Ciclosporin  

Acetazolamide and alcohol

Alcohol should be avoided 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.

Acetazolamide vs Diamox

Diamox is a brand name for acetazolamide, which is the generic name for the drug. As of April 2015 it is not longer possible to buy Diamox in the UK. The treatment is now sold simply as ‘acetazolamide’, and contains the same dosage and ingredients. 

Alternatives to Acetazolamide

There are measures for managing altitude sickness which should be followed 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:

• Avoid climbing more than 300-500m per day
• If climbing in high altitudes, take a day to rest after every 600-900m ascent, or rest after every 3-4 days.
• Avoid drinking alcohol or smoking prior to and during your ascent
• Maintain a light but high calorie diet
• Drink plenty of water at all times

What should you do if you begin to experience altitude sickness?

If you begin to experience symptoms of altitude sickness, see the following measures:

• Stopping your ascent for at least 24-48 hours
• Drink plenty of water
• Avoid strenuous activity or exercise, and rest completely for 24 hours
• Avoid smoking and drinking alcohol
• Take painkillers such as Paracetamol or Ibuprofen to relieve your headache
• Take anti-sickness such as Promethazine if you feel nauseous  

Can you buy Acetazolamide over the counter?

Acetazolamide cannot be bought over the counter, but 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.

How does Acetazolamide affect blood pressure?

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 in particular. 

Does Acetazolamide help Ménière’s disease?

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’s 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 are used by some to treat Ménière’s disease, relieving the inner ear fluid build-up and reducing vertigo and hearing loss.  

Can Acetazolamide be used for migraines?

Those who suffer from migraines triggered by travelling to high altitudes may find that taking acetazolamide 2-3 days before their trip prevents migraines from occurring. However, there is little evidence to suggest that taking acetazolamide is beneficial to those who suffer from migraines that are unrelated to altitude. 

Sources

• Patient Information Leaflet
• NHS > Altitude Sickness
• WebMD > Diamox
• Effects of acetazolamide on blood pressure
• PharmacyTimes > Ménière’s disease
• MedlinePlus