Article: Acetazolamide

Acetazolamide
Systematic (IUPAC) name
N-(5-(aminosulfonyl)-1,3,4-thiadiazol-2-yl)-acetamide
Identifiers
CAS number	59-66-5
ATC code	S01EC01
PubChem	1986
DrugBank	APRD00119
Chemical data
Formula	C4H6N4O3S2
Mol. weight	222.248 g/mol
Pharmacokinetic data
Bioavailability	?
Metabolism	None
Half life	3 to 9 hours
Excretion	Renal
Therapeutic considerations
Pregnancy cat.	B3(AU) C(US)
Legal status	POM(UK) ℞-only(US)
Routes	Oral, IV

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 and cystinuria. For glaucoma sufferers, the drug decreases fluid formation around the eye resulting in lower internal pressure on the eye. Acetazolamide can only be obtained by prescription and is available as a generic drug.

Uses

General

Acetazolamide is used in glaucoma and epilepsy. 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.

Altitude sickness

Acetazolamide has been shown to relieve mild cases of altitude sickness in some people. The drug forces the kidneys to excrete bicarbonate, the base form of carbon dioxide thus counteracting the effects of hyperventilation that occurs at altitude. Some take acetazolamide prophylactically, anywhere between 125 milligrams (mg) to 500 mg per day. Others only take it when symptoms begin to appear so they can tell whether the drug really has any benefits for them. Acetazolamide can also be taken to treat sleep apnea that may develop at higher elevations as it stimulates the respiratory system to breathe more regularly. Note that acetazolamide is not an immediate quick fix – it speeds up acclimatization which in turn helps to relieve symptoms. This may take up to a day or two without any further rapid ascent.

Side-effects

Common side effects of using this drug include numbness and tingling in the fingers and toes, and taste alterations (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. Everyone will experience more frequent urination as a result of using acetazolamide. One should drink more fluids than usual to prevent dehydration and headaches.

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.