Acetazolamide: Uses, Indications, Dosages, Precautions, Contraindications, Side Effects & Interactions

Acetazolamide

(a-set-a-zole-a-mide)
Classification 
Pharmacotherapeutic: Sulfonamide derivative
Clinical: Diuretic carbonic anhydrase inhibitor; antiglaucoma agent, antiepileptic

Diamox

Diamox Sequels

Acetazolam

CATEGORY AND SCHEDULE

Pregnancy Risk Category: C

Do not confuse:

acetaZOLAMIDE/ acetoHEXAMIDE

Diamox/Dobutrex/Trimox

General Information

Acetazolamide belongs to the group of sulfonamide derivatives which inhibit diuretic carbonic anhydrase; antiglaucoma agent, antiepileptic group of drugs. They are effective for the adjunctive treatment of edema due to congestive heart failure, drug-induced edema, central brain epilepsy (small non-localized seizures), chronic simple (open-angle) glaucoma and secondary glaucoma, and preoperatively in acute angle-closure glaucoma when delay of surgery is desired to lower intraocular pressure and used orally for acute mountain sickness

Acetazolamide can cause severe reactions, such as: Long-term therapy can cause acidosis. Occasionally, nephrotoxicity / hepatotoxicity occurs, manifesting as dark urine / stools, back pain, jaundice, dysuria, crystalluria, renal colic / calculi. Bone marrow depression may be manifested as aplastic anemia, thrombocytopenia, thrombocytopenic purpura, leukopenia, agranulocytosis, haemolytic anemia. Rare but severe hypersensitivity reactions similar to sulfonamides; Stevens-Johnson syndrome; toxic epidermal necrolysis and anaphylaxis

Action

A carbonic anhydrase inhibitor that reduces the formation of hydrogen and bicarbonate ions from carbon dioxide and water by inhibiting the enzyme carbonic anhydrase in the proximal renal tubule, thus promoting the renal excretion of sodium, potassium, bicarbonate and water. Ocular: reduces the rate of aqueous humor formation, lowers intraocular pressure

Therapeutic Effect

Produces anticonvulsant activity by retarding neuronal conduction in the brain, produces a diuretic effect generally

Availability (Rx)

Capsules, Sustained Release: 500 mg (Diamox Sequels)

Powder for Injection; Lyophilized: 500 mg

Tablets: 125 mg, 250 mg

Uses

Open-angle glaucoma, angle closure glaucoma (preoperatively if surgery delayed), seizures (petit mal, grand mal, mixed, absence), edema in CHF, product-induced edema, acute altitude sickness

Unlabeled uses: Urine alkalinization, metabolic alkalosis in mechanical ventilation, decrease CSF production in infants with hydrocephalus, familial periodic paralysis, nystagmus

Precautions

Pregnancy C, breastfeeding, hypercalciuria, COPD, respiratory acidosis, pulmonary obstruction/emphysema

Make sure to tell your doctor if:

• You have long-term liver or kidney problems

• You have pulmonary trouble

• You have GI disease

• You are taking other medicines

Indications and Dosages

‣ To Treat Chronic simple (open-angle) glaucoma

PO

• Adults: 250 mg 1-4 times/day, not to exceed 1 g/day. Extended-Release:

500 mg 1-2 times/day usually given in morning and evening, not to exceed 1 g/day

‣ To Treat Secondary glaucoma, preop treatment of closed-angle glaucoma (short term)

PO

• Adults: Initially 500 mg; then 125-250 mg q4h

IV

• Adults: 500 mg IV for acute lowering of IOP in patients unable to take PO. If needed, may repeat the dose in 2-4 h

‣ To Treat Edema in CHF

PO/IV

• Adult: 250-375 mg/day or 5 mg/kg in am, give for 2 days, then 1-2 days drug-free

‣ To Treat Epilepsy

PO

• Adults. Optimum range is 375-1000 mg/day in 1-4 divided doses, unless

given with another anticonvulsant therapy where initial dosage should be 250 mg/day

‣ To Treat Seizures

PO/IV

• Adult: 8-30 mg/kg/day in 1-4 divided doses, usual range 375-1000 mg/day; EXT REL not recommended in seizures

• Child: 8-30 mg/kg/day in divided doses tid or qid, or 300-900 mg/m2/day, not to exceed 1 g/day

‣ To Treat a cute mountain sickness

PO

• Adults: 500-1000 mg/day in divided doses using tablets or sustainedrelease

capsules. If possible, begin 24-48 h before ascent; continue at least 48 h at high altitude

‣ To Treat Diuresis in CHF

PO/IV

• Adults: Initially 250-375 mg (5 mg/kg) every morning, then given on alternate days or for 2 days alternating with 1 day of rest. Use lowest effective dosage

‣ Dosage in Renal Impairment

PO/IV

• Adult: CCr 50-80 ml/min, give dose ≥6 hr reg rel of IV; CCr 10-50 ml/min, give dose q12hr; CCr ＜10 ml/min, avoid use

Pharmacokinetics

SR: Absorption 3-6 h; onset 2 h; peak activity attained 3-6 h; duration 18-24 h

IR: Absorption 1-4 h; onset 1-1.5 h; peak activity attained 1-4 h; duration 8-12 h

IV: Onset 2 min; peak activity attained 15 min; duration 4-5 h. Excreted unchanged in urine. Removed by hemodialysis. Half-life: 2.4-5.8 h

Implementation

• Give in am to avoid interference with sleep

• Administer fluids 2-3 L/day to prevent renal calculi, unless contraindicated

• Potassium replacement if potassium level is ,3.0 ml/dl

PO route

• Do not crush or chew ext rel caps; caps may be opened and sprinkled on food

• Give with food; if nausea occurs, crush tabs and mix with sweet substance to counteract bitter taste

IV route

• Do not use solution that is yellow or has a precipitate or crystals

• Dilute 500 mg of product/5 ml or more sterile water for inj: use within 24 hr, give at 100-500 mg/min

IV, direct route

• Give over 1 min or more Intermittent IV infusion route

• May be added to NS, D5W, D10W, 0.45% NaCl; give over 15-30 min

• Store in cool, dark area, use reconstituted solution within 24 hr

Contraindications

Hypersensitivity to acetazolamide, product components, or to other

sulfonamides; severe renal disease, hepatic cirrhosis, decreased sodium or potassium serum levels, adrenal insufficiency, hypochloremic acidosis, severe pulmonary obstruction with increased risk of acidosis. Long-term use is

contraindicated in patients with chronic noncongestive angle-closure glaucoma

Cautions: Acidosis, anorexia, bone marrow suppression, confusion, crystalluria, drowsiness, fever, hemolytic anemia, hypokalemia (ECG changes, fatigue, muscle weakness, vomiting), paresthesias, photosensitivity, polyuria, rash, renal calculus, thrombocytopenic purpura

Interactions

Individual drugs

• Amphotericin B, corticotropin, ACTH: increased hypokalemia

• Arsenic trioxide, levomethadyl: increased cardiac toxicity if hypokalemia develops

• CarBAMazepine, ethotoin: increased osteomalacia

• CycloSPORINE: increased toxicity

• Diflunisal: increased side effects

• Lithium: increased excretion of lithium

• Methenamine: decreased acetaZOLAMIDE effect

• Primidone: decreased primidone level

• Topiramate: increased renal stone formation, heat stroke, avoid concurrent use

Drug classifications

• Amphetamines: increased action

• Anticholinergics, folic acid antagonists: increased action of each product

• Cardiac glycosides: increased cardiac toxicity if hypokalemia develops

• Corticosteroids: increased hypokalemia

• Flecainide, memantine, phenytoin, procainamide, quiNIDine, mecamylamine, mexiletine: increased effect of each product

• Salicylates: increased toxicity

Drug/laboratory tests

• Increased: glucose, bilirubin, calcium, uric acid

• Decreased: thyroid iodine uptake

• False positive: urinary protein, 17-hydroxysteroids

Drugs/food

• None known

Herbal

• None significant

Side effects

• CNS: Ataxia, confusion, depression, disorientation, dizziness, drowsiness, fatigue, fever, flaccid paralysis, headache, lassitude, malaise, nervousness, paresthesia, seizures, tremor, weakness

• EENT: Altered taste, tinnitus, transient myopia

• GI: Anorexia, constipation, diarrhea, hepatic dysfunction, melena, nausea, vomiting

• GU: Crystalluria, decreased libido, glycosuria, hematuria, impotence, nephrotoxicity, phosphaturia, polyuria, renal calculi, renal colic, urinary frequency

• HEME: Agranulocytosis, hemolytic anemia, leukopenia, pancytopenia, thrombocytopenia, thrombocytopenic purpura

• SKIN: Photosensitivity, pruritus, rash, Stevens-Johnson syndrome, urticaria

• Other: Acidosis, hyperuricemia, hypokalemia, weight loss

 

Nursing considerations

Baseline assessment

• Observe and record behavior

• Assess psychological status, such as: depression, sleep patterns, appearance, drowsiness, dizziness; loss of appetite; transient myopia; unusually tired/weak; increased urination/ frequency; altered taste (metallic); nausea; numbness or tingling in extremities, lips, mouth

• Monitor hepatic/renal function tests, blood counts should be performed periodically, for patients on long-term therapy

Intervention/evaluation

• Obtain baseline CBC and platelet count before use and monitor during therapy

• Periodic monitoring of electrolytes is recommended

• Assess appearance, behavior, speech pattern, level of interest, mood. Monitor B/P for hypotension, pulse, arrhythmias

Equipment must be available for anaphylaxis

• Assess patient for tinnitus, hearing loss, ear pain; periodic testing of hearing is needed when high doses of this product are given by IV route

• Assess for seizures: type, location, duration; provide seizure precautions

• Assess fluid volume status: I&O ratio and record, count or weigh diapers as appropriate, distended neck veins, crackles in lung, color, quality, and specific gravity of urine, skin turgor, adequacy of pulses, moist mucous membranes, bilateral lung sounds, peripheral pitting edema; dehydration symptoms of decreasing output, thirst, hypotension, dry mouth, and mucous membranes should be reported

• Monitor electrolytes: potassium, sodium, calcium, magnesium; also include BUN, blood pH, ABGs, uric acid, CBC, blood glucose

• Assess B/P before and during therapy with patient lying, standing, and sitting as appropriate; orthostatic hypotension can occur rapidly

• Monitor blood, urine glucose in diabetic patients; glucose levels may be increased

• Assess for eye pain, change in vision when using product for intraocular pressure

• Assess neurologic status when using product for seizures

• Assess for decreased symptoms of acute mountain sickness: headache, nausea, vomiting, dizziness, fatigue, drowsiness, shortness of breath, insomnia

• Assess for cross-sensitivity between other sulfonamides and this product

Evaluation

Positive therapeutic result

• Decreased intraocular pressure (glaucoma)

• Decreased edema in feet, legs, sacral area daily (CHF)

• Decreased frequency of seizures

• Prevention of altitude sickness

Patient/family teaching

• Teach patient to take the medication early in the day to prevent nocturia

• Inform patient that acetazolamide tablets may be crushed and suspended in chocolate or another sweet syrup. Or, one tablet may be dissolved in 10 ml hot water and added to 10 ml honey or syrup

• Teach patient not to use alcohol or any OTC medications without prescriber’s approval; serious product reactions may occur

• Instruct patient who takes high doses of salicylates to notify prescriber immediately about evidence of salicylate toxicity, such as anorexia, tachypnea, and lethargy

• Advise patient to wear protective clothing and sunscreen in the sun to prevent photosensitivity

• Advise patient to avoid hazardous activities if dizziness or drowsiness occurs.

• Emphasize the need to contact prescriber immediately if muscle cramps, weakness, nausea, dizziness, or numbness, rapid weight changes, change in stools, rash, sore throat, bleeding/bruising, Stevens-Johnson syndrome, toxic epidermal necrolysis (red rash that spreads, blistering) occur

• Avoid prolonged sun exposure

• Teach patient to take own B/P and pulse and record

• Teach patient to continue taking medication even if feeling better; this product controls symptoms but does not cure the condition

• Teach patient to see ophthalmologist periodically; glaucoma is a slow process

• Advise patient to increase fluids to 2-3 L/day if not contraindicated

Treatment of Overdose:

Lavage if taken orally, monitor electrolytes, administer dextrose in saline, monitor hydration, CV, renal status