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Acetazolamide Side Effects – Uses, Indications, Warning

Acetazolamide Side Effects/Acetazolamide 500mg Oral Tablet/Acetazolamide is a sulfonamide derivative with diuretic, antiglaucoma, and anticonvulsant properties. Acetazolamide is a non-competitive inhibitor of carbonic anhydrase, an enzyme found in cells in the proximal tube of the kidney, the eye, and glial cells. Inhibition of this enzyme in the kidney prevents excretion of hydrogen, leading to increased bicarbonate and cation excretion and increased urinary volume, which results in an alkaline diuresis. Acetazolamide reduces the concentration of bicarbonate, resulting in a decreased synthesis of aqueous humor in the eye, thereby lowering intraocular pressure. Although its mechanism of action is unknown, acetazolamide has anti-convulsant properties resulting from indirect effects secondary to metabolic acidosis or direct effects on neuronal transmission. Acetazolamide also produces respiratory stimulant effects in response to changes to both carbon dioxide and oxygen tension levels within the lungs.

Acetazolamide and methazolamide are carbonic anhydrase inhibitors used as diuretics and in the therapy of glaucoma. Both acetazolamide and methazolamide have been linked to rare cases of clinically apparent drug-induced liver disease.

Mechanism of Action

The anticonvulsant activity of Acetazolamide may depend on direct inhibition of carbonic anhydrase in the CNS, which decreases carbon dioxide tension in the pulmonary alveoli, thus increasing arterial oxygen tension. The diuretic effect depends on the inhibition of carbonic anhydrase, causing a reduction in the availability of hydrogen ions for active transport in the renal tubule lumen. This leads to alkaline urine and an increase in the excretion of bicarbonate, sodium, potassium, and water.

Acetazolamide is a sulfonamide derivative with diuretic, antiglaucoma, and anticonvulsant properties. Acetazolamide is a non-competitive inhibitor of carbonic anhydrase, an enzyme found in cells in the proximal tube of the kidney, the eye, and glial cells. Inhibition of this enzyme in the kidney prevents excretion of hydrogen, leading to increased bicarbonate and cation excretion and increased urinary volume, which results in an alkaline diuresis. Acetazolamide reduces the concentration of bicarbonate, resulting in a decreased synthesis of aqueous humor in the eye, thereby lowering intraocular pressure. Although its mechanism of action is unknown, acetazolamide has anti-convulsant properties resulting from indirect effects secondary to metabolic acidosis or direct effects on neuronal transmission. Acetazolamide also produces respiratory stimulant effects in response to changes to both carbon dioxide and oxygen tension levels within the lungs.

Indication of Acetazolamide

For adjunctive treatment of: edema due to congestive heart failure; drug-induced edema; centrencephalic epilepsies; chronic simple (open-angle) glaucoma
For adjunctive treatment of edema due to congestive heart failure or drug-induced edema.
Glaucoma
Acute Mountain Sickness
Hydrocephalus
Epilepsy
Edema
Hypokalemic Periodic Paralysis
Mountain Sickness / Altitude Sickness
Pseudotumor Cerebri
Seizure Prevention
For the prevention or amelioration of symptoms associated with acute mountain sickness despite gradual ascent.

Therapeutic Uses

Anticonvulsants; Carbonic Anhydrase Inhibitors; Diuretics
Carbonic anhydrase inhibitors are indicated primarily as adjuncts to other agents in the treatment of open-angle (chronic simple) glaucoma and secondary glaucoma, and to lower intraocular pressure prior to surgery for some types of glaucoma.
Acetazolamide is used to lower intraocular pressure in the treatment of malignant (ciliary block) glaucoma, which may occur after inflammation surgery, trauma, or use of miotics. /NOT included in US product labeling/
Acetazolamide is indicated as an adjunct to other anticonvulsants in the management of absence seizures (petit mal), generalized tonic-clonic seizures (grand mal), mixed seizure patterns. It may be especially useful for intermittent therapy in females who experience increased seizure activity at the time of menstruation.
Oral acetazolamide is indicated to decrease the incidence and/or severity of symptoms (such as headache, nausea, shortness of breath, dizziness, drowsiness, and fatigue) associated with acute altitude sickness in mountain climbers who are attempting rapid ascent and in those who are very susceptible to altitude sickness despite gradual ascent. Gradual ascent is desirable for the prevention of acute altitude sickness even when acetazolamide is used. However, prompt descent may still be necessary if severe manifestations of acute altitude sickness, such as pulmonary edema or cerebral edema, occur.
Acetazolamide is used to treat both the hypokalemic and hyperkalemic forms of familial periodic paralysis. It terminates the acute attacks and, with chronic use, prevents their recurrence. It may be the drug of choice in the hypokalemic form of the condition.
Parenteral acetazolamide is used to produce a forced alkaline diuresis as a method of increasing the elimination of certain weakly acidic medications.
Oral acetazolamide is used to alkalinize the urine as a means of preventing the occurrence or recurrence of uric acid renal stones, especially in patients receiving uricosuric antigout agents, or of cysteine renal stones.
Acetazolamide has also been used to prevent or counteract metabolic alkalosis, including that which may occur following open-heart surgery; however, it is no longer used for these indications.
Acetazolamide has also been used as a diuretic in the treatment of edema due to congestive heart disease and drug-induced edema. However, it has been replaced by newer diuretics for these indications
A placebo-controlled study of the therapy of acute altitude sickness in 12 mountain climbers, 6 of whom were given 250 mg of oral acetazolamide every 8 hr for 2 doses, is reported. After 24 hr, the patients treated with acetazolamide were asymptomatic, whereas those given the placebo still had acute altitude sickness. The alveolar to arterial oxygen pressure difference decor slightly over 24 hr in the acetazolamide group but incr slightly in the placebo group. Acetazolamide improved the arterial partial oxygen pressure over 24 hr when compared with placebo. It was concluded that in established cases of acute altitude sickness, treatment with acetazolamide relieves symptoms, improves arterial oxygenation, and prevents further impairment of pulmonary gas exchange.

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Contraindications of Acetazolamide

Hyperchloremic acidosis
Hypokalemia (low blood potassium)
Hyponatremia (low blood sodium)
Adrenal insufficiency
Impaired kidney function
Hypersensitivity to acetazolamide or other sulfonamides.
Marked liver disease or impairment of liver function, including cirrhosis because of the risk of development of hepatic encephalopathy. Acetazolamide decreases ammonia clearance
type 1 diabetes mellitus
a condition where the adrenal glands produce less hormones called Addison’s disease
a type of joint disorder due to excess uric acid in the blood called gout
respiratory acidosis, an acid-base disorder
a blood disorder
decreased lung function
liver problems
severe liver disease
renal tubular acidosis
recurrent calcium-containing kidney stones
decreased kidney function
hyperchloremic acidosis

Dosage of Acetazolamide

Strengths: 500 mg; 125 mg; 250 mg

Edema

Initial dose: 250 to 375 mg orally/IV once a day
If after initial response there is a lack of response, hold therapy for a day
Maintenance dose: One dose every other day or once a day for 2 days alternating with a day of rest

Acute Mountain Sickness

500 to 1000 mg orally per day in divided doses
Guideline dose: 125 mg orally twice a day
AMS Treatment: Guideline dose: 250 mg orally twice a day
May use immediate-release or extended-release as appropriate for Acute Mountain Sickness (AMS)/High Altitude Cerebral Edema (HACE) Prevention

Glaucoma

Open-Angle Glaucoma

Immediate-release (IR) tablets: 250 to 1000 mg orally per day; amounts over 250 mg should be administered in divided doses
Extended-release (ER) capsules: 500 mg orally 2 times a day
Maintenance: Adjust doses individually based on symptomatology and ocular tension; for patients inadequately controlled on ER capsules 1 g/day, may supplement with IR tablets
Doses in excess of 1 g/24 hour generally do not produce increased effects

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Preoperatively in Closed-Angle Glaucoma

Various regimens have been used including 250 mg orally every 4 hours; 250 mg orally twice a day; OR 500 mg orally followed by 125 mg or 250 mg orally every 4 hours

Glaucoma (Open Angle)

Open-Angle Glaucoma

Immediate-release (IR) tablets: 250 to 1000 mg orally per day; amounts over 250 mg should be administered in divided doses
Extended-release (ER) capsules: 500 mg orally 2 times a day
Maintenance: Adjust doses individually based on symptomatology and ocular tension; for patients inadequately controlled on ER capsules 1 g/day, may supplement with IR tablets
Doses in excess of 1 g/24 hour generally do not produce increased effects

Preoperatively in Closed-Angle Glaucoma

Various regimens have been used including 250 mg orally every 4 hours; 250 mg orally twice a day; OR 500 mg orally followed by 125 mg or 250 mg orally every 4 hours

Seizure Prophylaxis

Initial dose: 8 to 30 mg/kg orally/IV in divided doses
Range: 375 to 1000 mg per day
Initial dose for patients on other anticonvulsants: 250 mg orally/IV once a day

Pediatric Dose

Acute Mountain Sickness

12 years or older:

Extended-release capsules: 500 mg orally once or twice a day
Guideline dose (immediate-release): 2.5 mg/kg orally every 12 hours
Maximum: 125 mg per dose

Glaucoma

12 years or older

Extended-release (ER) capsules: 500 mg orally 2 times a day
Doses in excess of 1 g/24 hour generally do not produce increased effects.

Glaucoma (Open Angle)

12 years or older

Extended-release (ER) capsules: 500 mg orally 2 times a day

Side Effects of Acetazolamide

The most Common

paresthesias, “tingling” feeling in the extremities,
some loss of appetite,
polyuria,
occasional drowsiness,
confusion and photosensitivity
papular or erythematous skin eruptions,
nausea,
acidosis and blood dyscrasias.
myopia, malaise syndrome,
fatigue,
anorexia,
loss of weight,
depression and loss of libido;
gastrointestinal distress,
elevated blood urate,
acute gouty arthritis skin rashes and hair loss or excess growth of hair.

Common

Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
Signs of too much acid in the blood (acidosis) like confusion; fast breathing; fast heartbeat; a heartbeat that does not feel normal; very bad stomach pain, upset stomach, or throwing up; feeling very sleepy; shortness of breath; or feeling very tired or weak.
Signs of electrolyte problems like mood changes, confusion, muscle pain or weakness, a heartbeat that does not feel normal, seizures, not hungry, or very bad upset stomach or throwing up.
Change in eyesight.
Change in hearing.
Ringing in ears.

Rare

Paresthesias, hearing dysfunction or tinnitus, anorexia, altered taste, nausea, vomiting, diarrhea, polyuria, drowsiness, confusion.
A burning, numbness, or tingling feeling that is not normal.
Pain when passing urine or blood in the urine.
Not able to pass urine or change in how much urine is passed.
Muscle weakness.
Change in balance.
Trouble moving around.
Upset stomach or throwing up.
Change in taste.
Diarrhea.
Not hungry.
Blurred eyesight.
Feeling dizzy, sleepy, tired, or weak.
Headache.
Flushing.
Feeling nervous and excitable.

Drug Interactions of Acetazolamide

View interaction reports for acetazolamide and the medicines listed below.

diphenhydramine
CoQ10 ubiquinone
duloxetine
Fish Oil (omega-3 polyunsaturated fatty acids)
furosemide
pregabalin
esomeprazole
acetaminophen / hydrocodone
acetaminophen
albuterol
magnesium salicylate
metformin
methazolamide
dichlorphenamide
dofetilide
dronedarone
droperidol
citalopram
clobazam
clonazepam
clorazepate
clozapine
corticorelin
corticotropin
cortisone
montelukast
levothyroxine
topiramate
acetaminophen
Vitamin B12 (cyanocobalamin)
Vitamin C (ascorbic acid)
Vitamin D2 (ergocalciferol)
Vitamin D3 (cholecalciferol)
ondansetron
cetirizine

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Pregnancy Category

US FDA pregnancy category – C
Pregnancy category – B3 in Australia

Pregnancy

Acetazolamide is pregnancy category B3 in Australia, which means that studies in rats, mice and rabbits in which acetazolamide was given intravenously or orally caused an increased risk of fetal malformations, including defects of the limbs.^[rx] Despite this, there is insufficient evidence from studies in humans to either support or discount this evidence.^[rx]

Lactation

Limited data are available on the effects of nursing mothers taking acetazolamide. Therapeutic doses create low levels of breast milk and are not expected to cause problems in infants.^[rx]

Before taking acetazolamide,

tell your doctor and pharmacist if you are allergic to acetazolamide, sulfa drugs, diuretics (‘water pills’), or any other drugs.
tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially amphetamines, aspirin, cyclosporine (Neoral, Sandimmune), medications for depression or irregular heartbeat, diflunisal (Dolobid), digoxin (Lanoxin), diuretics (‘water pills’), lithium (Eskalith, Lithobid), phenobarbital, primidone (Mysoline), and vitamins.
tell your doctor if you have or have ever had heart, liver, or kidney disease; or diabetes.
tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while taking acetazolamide, call your doctor immediately.
if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking acetazolamide.
you should know that this drug may make you drowsy. Do not drive a car or operate machinery until you know how this drug affects you.
remember that alcohol can add to the drowsiness caused by this drug.
plan to avoid unnecessary or prolonged exposure to sunlight and to wear protective clothing, sunglasses, and sunscreen. Acetazolamide may make your skin sensitive to sunlight.

References

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Acetazolamide Side Effects – Uses, Indications, Warning

Acetazolamide Side Effects – Uses, Indications, Warning

Mechanism of Action