Acetazolamide (extended-release capsule)

Acetazolamide (extended-release capsule)

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Clinical data
Pregnancy category	AU: B3 US: C (Risk not ruled out)
Routes of administration	Oral, IV
ATC code	S01EC01 (WHO)
Legal status
Legal status	UK: POM (Prescription only) US: ℞-only
Pharmacokinetic data
Metabolism	None
Elimination half-life	3 to 9 hours
Excretion	Renal
Identifiers
IUPAC name N-(5-(aminosulfonyl)-1,3,4-thiadiazol-2-yl)-acetamide
CAS Number	59-66-5
PubChem CID	1986
DrugBank	APRD00119
E number	{{#property:P628}}
ECHA InfoCard	{{#property:P2566}}
Chemical and physical data
Formula	C4H6N4O3S2
Molar mass	222.248 g/mol

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Overview

Acetazolamide, sold under the trade name Diamox, is a carbonic anhydrase inhibitor that is used to treat glaucoma, epileptic seizures, benign intracranial hypertension, altitude sickness, cystinuria, and dural ectasia. Acetazolamide is available as a generic drug and is also used as a diuretic.

Uses

General

Acetazolamide is often used in the treatment of various diseases. For glaucoma sufferers, the drug decreases fluid formation in the eye resulting in lower intraocular pressure. In epilepsy, its main use is in absence seizures, with some benefit in other seizure syndromes. It is also used to decrease generation of cerebrospinal fluid in benign intracranial hypertension and has also shown efficacy in autosomal dominant hyperkalemic periodic paralysis. It has also been demonstrated in drug trials to relieve symptoms associated with dural ectasia in indivduals with Marfan Syndrome.

Acute mountain sickness

Acetazolamide is best taken prophylactically, anywhere between 125 milligrams (mg) to 500 mg per day, starting a few days before going to the higher altitude. The drug forces the kidneys to excrete bicarbonate, the conjugate base of carbonic acid. By increasing the amount of bicarbonate excreted in the urine, the blood becomes more acidic. Acidifying the blood stimulates ventilation, which is beneficial during acclimatization. Others only take it when symptoms begin to appear so they can tell whether the drug really has any benefits for them. Whereas some people have reported that it relieves mild cases of acute mountain sickness, it is best taken prophylactically.

Note that acetazolamide is not an immediate fix for acute mountain sickness; it speeds up acclimatization which in turn helps to relieve symptoms. This may take up to a day or two, and requires waiting without any further rapid ascent. It is often advisable to descend if even mild acute mountain sickness is experienced. If serious sickness is encountered, descent is considered mandatory unless other circumstances present greater danger.

Side-effects

Common side effects of using this drug include numbness and tingling in the fingers and toes, and taste alterations (parageusia), especially for carbonated drinks; both are usually due to mild hypokalemia (low potassium levels). Some may also experience blurred vision but this usually disappears shortly after stopping the medication. Acetazolamide also increases the risk of developing calcium oxalate and calcium phosphate kidney stones. Everyone will experience more frequent urination as a result of using acetazolamide. One should drink more fluids than usual to prevent dehydration and headaches. Acetazolamide prolongs the effects of amphetamines and related drugs.

Contraindications

Acetazolamide should not be taken by individuals if:

• They have sickle cell anemia
• They are allergic to sulfa medications
• They are allergic to any carbonic anhydrase inhibitor
• They have liver or kidney disease
• They have adrenal gland failure (i.e. Addison's disease)
• They have diabetes
• They are pregnant or nursing mothers

Myths

• 'Acetazolamide covers up symptoms.' Not so: Acetazolamide speeds up acclimatization which in turn helps to alleviate symptoms. However, if you still feel sick, you need to stop ascending immediately.
• 'Acetazolamide prevents acute mountain sickness from getting worse.' Not so: If your symptoms are not improving, continued ascent can lead to HAPE or HACE.
• 'Stopping the drug causes symptoms to worsen.' Not so: Your body will just return to its own acclimatization rate. If you are already acclimatized, the drug will not change that fact.

References

• Going Higher: Oxygen Man and Mountains by Charles Houston, M.D., Fifth Edition, 2005. ISBN 0-89886-631-6.
• Complete Guide to Prescription & Non-Prescription Drugs by H. Winter Griffen, M.D., Sixth edition, 1989. ISBN 0-89586-754-0.
• http://www.ismmed.org/np_altitude_tutorial.htm
• Dural Ectasia in the Marfan Spine: Symptoms and Treatment. November 27, 2006. http://www.spineuniverse.com/displayarticle.php/article922.html
• Diamox - Quoted from the Physician's Desk Reference 1993 http://www.climber.org/gear/diamox.html