General

Pronunciation
a-set-a-ZOLE-a-mide

Trade Name(s)

• Acetazolam [Canada]

• AK-Zol

• Apo-Acetazolamide [Canada]

• Dazamide

• Diamox

• Diamox Sequels

• Storzolamide

Pregnancy Category
Category C

Ther. class.
anticonvulsants
antiglaucoma agents
diuretics
ocular hypotensive agent

Pharm. class.
carbonic anhydrase inhibitors

Indications

• Lowering of intraocular pressure in the treatment of glaucoma

• Management of acute altitude sickness

Unlabelled Use(s):

• Diuretic

• Adjunct to the treatment of refractory seizures

• Reduce cerebrospinal fluid production in hydrocephalus

• Prevention of renal calculi composed of uric acid or cystine

Action

• Inhibition of carbonic anhydrase in the eye results in decreased secretion of aqueous humor

• Inhibition of renal carbonic anhydrase, resulting in self-limiting urinary excretion of sodium, potassium, bicarbonate, and water

• CNS inhibition of carbonic anhydrase and resultant diuresis may decrease abnormal neuronal firing

• Alkaline diuresis prevents precipitation of uric acid or cystine in the urinary tract

Therapeutic Effect(s):

• Lowering of intraocular pressure

• Control of some types of seizures

• Prevention and treatment of acute altitude sickness

• Prevention of uric acid or cystine renal calculi

Pharmacokinetics

Absorption: Dose dependent; erratic with doses >10 mg/kg/day

Distribution: Crosses the placenta and blood-brain barrier; enters breast milk

Protein Binding: 95%

Metabolism and Excretion: Excreted mostly unchanged in urine

Half-life: 2.4–5.8 hr

TIME/ACTION PROFILE (lowering of intraocular pressure)

ROUTE	ONSET	PEAK	DURATION
PO	1–1.5 hr	2–4 hr	8–12 hr
PO-ER	2 hr	8–18 hr	18–24 hr
IV	2 min	15 min	4–5 hr

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity or cross-sensitivity with sulfonamides may occur

• Hepatic disease or insufficiency

• Concurrent use with ophthalmic carbonic anhydrase inhibitors (brinzolamide, dorzolamide) is not recommended

• OB: Avoid during first trimester of pregnancy

Use Cautiously in:

• Chronic respiratory disease

• Electrolyte abnormalities

• Gout

• Renal disease (dosage reduction necessary for ClCr <50 ml/min)

• Diabetes mellitus

• OB: Use with caution during second or third trimester of pregnancy

• Lactation: Safety not established

Adverse Reactions/Side Effects

CNS: depression, tiredness, weakness, drowsiness.

EENT: transient nearsightedness.

GI: anorexia, metallic taste, nausea, vomiting, melena.

GU: crystalluria, renal calculi.

Derm: STEVENS-JOHNSON SYNDROME, rashes.

Endo: hyperglycemia.

F and E: hyperchloremic acidosis, hypokalemia, growth retardation (in children receiving chronic therapy).

Hemat: APLASTIC ANEMIA, HEMOLYTIC ANEMIA, LEUKOPENIA.

Metabolic: weight loss, hyperuricemia.

Neuro: paresthesias.

Misc: ALLERGIC REACTIONS INCLUDING ANAPHYLAXIS.

*CAPITALS indicates life-threatening.
*italic indicates most frequent.

Interactions

Drug-Drug

• Excretion of barbiturates, aspirin, and lithium is and may lead to effectiveness

• Excretion of amphetamine, quinidine, procainamide, and possibly tricyclic antidepressants is and may lead to toxicity

• May cyclosporine levels

Route/Dosage

• PO (Adults):
Glaucoma (open angle)—250–1000 mg/day in 1–4 divided doses (up to 250 mg q 4 hr) or 500-mg extended-release capsules twice daily.
Epilepsy—4–16 mg/kg/day in 1–4 divided doses (maximum 30 mg/kg/day or 1 g/day).
Altitude sickness—250 mg 2–4 times daily started 24–48 hr before ascent, continued for 48 hr or longer to control symptoms.
Antiurolithic—250 mg at bedtime.
Edema—250–375 mg/day.
Urine alkalinization—5 mg/kg/dose repeated 2–3 times over 24 hrs.

• PO (Children):
Glaucoma—8–30 mg/kg (300–900 mg/m²/day) in 3 divided doses (usual range 10–15 mg/kg/day).
Edema—5 mg/kg/dose once daily.
Epilepsy—4–16 mg/kg/day in 1–4 divided doses (maximum 30 mg/kg/day or 1 g/day).

• PO (Neonates):
Hydrocephalus—5 mg/kg/dose q 6 hrs increased by 25 mg/kg/day up to a maximum of 100 mg/kg/day.

• IV (Adults):
Glaucoma (closed angle)—250–500 mg, may repeat in 2–4 hr to a maximum of 1 g/day.
Edema—250–375 mg/day.

• IV (Children):
Glaucoma—5–10 mg/kg q 6 hr, not to exceed 1 g/day.
Edema— 5 mg/kg/dose once daily.

• IV (Neonates):
Hydrocephalus—5 mg/kg/dose q 6 hrs increased by 25 mg/kg/day up to a maximum of 100 mg/kg/day.

Availability

• Tablets: 125 mg, 250 mg

• Extended-release capsules: 500 mg

• Injection: 500 mg/vial

Assessment

• Observe for signs of hypokalemia (muscle weakness, malaise, fatigue, ECG changes, vomiting)

» Assess for allergy to sulfonamides

Intraocular Pressure

• Assess for eye discomfort or decrease in visual acuity

Seizures

• Monitor neurologic status in patients receiving acetazolamide for seizures. Initiate seizure precautions

Altitude Sickness

• Monitor for decrease in severity of symptoms (headache, nausea, vomiting, fatigue, dizziness, drowsiness, shortness of breath). Notify health care professional immediately if neurologic symptoms worsen or if patient becomes more dyspneic and rales or crackles develop

Lab Test Considerations

• Serum electrolytes, complete blood counts, and platelet counts should be evaluated initially and periodically throughout prolonged therapy. May cause potassium, bicarbonate, WBCs, and RBCs. May cause serum chloride

» May cause in serum and urine glucose; monitor serum and urine glucose carefully in diabetic patients

» May cause false-positive results for urine protein and 17-hydroxysteroid tests

» May cause blood ammonia, bilirubin, uric acid, urine urobilinogen, and calcium. May urine citrate

Potential Nursing Diagnoses

• Disturbed sensory perception (visual) (Indications)

Implementation

• Do not confuse acetazolamide with acetohexamide

» Encourage fluids to 2000–3000 ml/day, unless contraindicated, to prevent crystalluria and stone formation

» A potassium supplement without chloride should be administered concurrently with acetazolamide

• PO: Give with food to minimize GI irritation. Tablets may be crushed and mixed with fruit-flavored syrup to minimize bitter taste for patients with difficulty swallowing. Extended-release capsules may be opened and sprinkled on soft food, but do not crush, chew, or swallow contents dry. Extended-release capsules are only indicated for glaucoma and altitude sickness; do not use for epilepsy or diuresis

• IM: Extremely painful; avoid if possible

• Direct IV: Dilute 500 mg of acetazolamide in at least 5 ml of sterile water for injection for a concentration of 100 mg/ml. Use reconstituted solution within 24 hr

• Rate: Not to exceed 500 mg/min

• Intermittent Infusion: Further dilute in D5W, D10W, 0.45% NaCl, 0.9% NaCl, Ringer's or lactated Ringer's solution, or combinations of dextrose and saline or dextrose and Ringer's solution

• Rate: Infuse over 4–8 hr

• Additive Compatibility:

» cimetidine

» ranitidine

• Additive Incompatibility:

» multiple parenteral multivitamins

Patient/Family Teaching

• Instruct patient to take as directed. Take missed doses as soon as possible unless almost time for next dose. Do not double doses. Patients on anticonvulsant therapy may need to gradually withdraw medication

» Advise patient to report numbness or tingling of extremities, weakness, rash, sore throat, unusual bleeding or bruising, or fever to health care professional. If hematopoietic reactions, fever, rash, or renal problems occur, carbonic anhydrase inhibitor therapy should be discontinued

» May occasionally cause drowsiness. Caution patient to avoid driving and other activities that require alertness until response to the drug is known

» Caution patient to use sunscreen and wear protective clothing to prevent photosensitivity reactions

• Intraocular Pressure: Advise patient of the need for periodic ophthalmologic exams; loss of vision may be gradual and painless

Evaluation/Desired Outcomes

• Decrease in intraocular pressure when used for glaucoma. If therapy is not effective or patient is unable to tolerate one carbonic anhydrase inhibitor, using another may be effective and more tolerable

• Decrease in the frequency of seizures

• Prevention of altitude sickness

• Prevention of uric acid or cystine stones in the urinary tract

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