Acetazolamide 250mg (formerly known as Diamox)

Buy Acetazolamide for Altitude Sickness

Acetazolamide is used for the treatment of mild early acute mountain sickness (headache, fatigue, light headedness, difficulty with sleep) to resolve symptoms, before a planned ascent can be resumed. It can also be used where rapid ascent without proper acclimatisation cannot be avoided and should be continued for 2-3 days after the final altitude is reached. The use of Acetazolamide for altitude sickness is off license, although it has been used in this setting for a long time. Its traditional use is for glaucoma, abnormal retention of fluids and epilepsy.

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  • Formerly known under the brand name Diamox
  • Widely used to treat altitude sickness
  • Not a substitute for proper acclimatisation
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Acetazolamide 250mg capsules contain the active substance acetazolamide. This belongs to a group of medicines known as carbonic anhydrase inhibitors, often used to treat abnormal retention of fluids (Acetazolamide acts as a diuretic). Acetazolamide increases the amount of urine produced and changes the acidity of the blood. This results in improved breathing and reduces fluid around the brain and in the lungs.


Do not take Acetazolamide:

  • if you are allergic (hypersensitive) to sulphonamides, sulphonamide derivatives including acetazolamide or any of the ingredients listed in the patient information leaflet
  • you have severe liver problems
  • you have or have ever had severe kidney problems
  • you have a particular type of glaucoma known as chronic non congestive angle closure glaucoma
  • you have Addison’s disease (reduced function of the adrenal glands – glands above the kidneys)
  • you have low blood levels of sodium and/or potassium or high blood levels of chlorine
Important Interactions

You must tell your doctor if you are taking, have recently taken or might take other medicines, in particular:

  • medicines for your heart such as cardiac glycosides (e.g. digoxin)
  • medicines to reduce blood pressure
  • medicines to thin your blood (e.g. warfarin)
  • medicines to lower the sugar in your blood (e.g. metformin, gliclazide)
  • medicines for epilepsy or fits (in particular, phenytoin, primidone or carbamazepine or topiramate)
  • Drugs which interfere with folic acid, e.g. methotrexate, pyrimethamine, or trimethoprim
  • steroids such as prednisolone
  • aspirin and related medicines, e.g. salicylic acid or choline salicylate for mouth ulcers
  • other drugs in the group of medicines called carbonic anhydrase inhibitors (e.g. dorzolamide or brinzolamide which are also used to treat glaucoma)
  • amphetamines (a stimulant), quinidine (treats an irregular heartbeat), methenamine (prevents urine infections) or lithium (treats severe mental problems)
  • sodium bicarbonate therapy (used to treat high states of acid in your body)
  • ciclosporin (used to suppress the immune system)
Side Effects
  • tingling sensation in the fingers and toes
  • some loss of appetite
  • taste disturbances
  • flushing
  • diarrhoea
  • headache
  • dizziness
  • fatigue
  • irritability
  • drowsiness or confusion
  • depression
Please Note

All medication can cause side effects. We have only listed a few to be aware of. Details of all side effects, including rare side effects to be aware of, are listed in the patient information leaflet (PIL). When completing your medical questionnaire, it is very important that you answer the questions truthfully. This is to ensure your doctor has a full picture of your medical history before prescribing. List all medicines you are already taking, including non-prescription and herbal medicines.


The only cure is acclimatisation or descent.

Looking after your medicine

Do not take medicines after the expiry date stamped on the pack. Keep all medicines out of the reach and sight of children.

Medicines are only intended to be used by the person they are prescribed for. Do not give your prescribed medicine to anybody else, even if they have the same symptoms as you. Medicines can be harmful if used by anybody other than the person they have been prescribed for.

References Acetazolamide 250mg Patient Information Leaflet
British National Formulary: acetazolamide

Please note that under the NHS, Acetazolamide treatment for altitude sickness is an unlicensed medication. This means that it is usually prescribed for the treatment of other conditions such as glaucoma and fluid retention. There is however scientific evidence that Acetazolamide is effective for the treatment of altitude sickness and it has long been prescribed for this. Your doctor will only prescribe Acetazolamide if they think it is safe to do so and they will provide detailed instructions on how to take this medicine.

Last reviewed & updated  16/01/2020   Authored  05/09/2010

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