acetazolamide (Diamox Sequels)
Classes: Anticonvulsants, Other; Antiglaucoma, Carbonic Anhydrase Inhibitors
Dosing and uses of Diamox Sequels (acetazolamide)
Adult dosage forms and strengths
tablet
- 125mg
- 250mg
powder for injection
- 500mg
capsule, extended-release
- 500mg
Glaucoma
Closed-angle (acute congestive) glaucoma
- 500 mg PO/IV, followed by 125-250 mg PO q4hr
- Sustained-release: 500 mg PO q12hr
Open-angle (chronic simple) glaucoma
- 250 mg-1 g PO/IV qDay or divided q6-12hr
- Sustained-release: 500 mg PO q12hr
Secondary glaucoma
- 500 mg PO/IV, followed by 125-250 mg PO q4hr
- Sustained-release: 500 mg PO q12hr
Acute Altitude Sickness
Immediate release: 500-1000 mg/day PO divided q8-12hr
Extended release: 500-1000 mg PO q12-24hr
Dosing considerations
- Start 24-48 hours before ascent and continue for 48 hours at high altitude or longer, to control symptoms if necessary
Congestive Heart Failure
CHF-associated edema
250-375 mg (5 mg/kg) PO qAm
Seizure
8-30 mg/kg/day PO qDay or divided q12hr
Drug-induced Edema
250-375 mg PO/IV qDay
Dosing considerations
- Do not increase dose if edema fails to decrease following an initial response; allow instead kidney recovery by skipping medication for a day; best results obtained when given on alternate days or for 2 days followed by a day of rest
Epilepsy
Tablet: 8-30 mg/kg/day PO qDay, OR divided q6-12 hr; not to exceed 30 mg/kg/day or 1 g/day
Extended-release capsule: Not recommended
Dosing Modifications
Renal impairment
- CrCl 10-50 mL/min: Administer no more frequently than q12hr
- CrCl <10 mL/min: Ineffective (avoid use)
- Hemodialysis: 20-50% dialyzable
- Peritoneal dialysis: Dose adjustment not necessary
Pediatric dosage forms and strengths
tablet
- 125mg
- 250mg
powder for injection
- 500mg
capsule, extended-release
- 500mg
Epilepsy
<12 years
- Safety and efficacy not established
>12 years
- Tablet: 8-30 mg/kg/day PO qDay or divided q6-12 hr; not to exceed 30 mg/kg/day or 1 g/day
- Extended-release capsule: Not recommended
Acute Altitude Sickness
<12 years
- Safety and efficacy not established
>12 years
- Immediate release: 500-1000 mg/day PO divided q8-12hr
- Extended release: 500-1000 mg PO q12-24hr
Dosing considerations
- Start 24-48 hr before ascent and continue for 48 hr at high altitude to control symptoms, if necessary
Geriatric dosage forms and strengths
250 mg PO qDay or q12hr; use lowest effective dose possible
Diamox Sequels (acetazolamide) adverse (side) effects
Frequency not defined
Confusion
Convulsions
Drowsiness
Flaccid paralysis
Malaise
Paresthesias
Photosensitivity
Urticaria
Anorexia
Diarrhea
Metallic taste
Nausea
Vomiting
Hepatic disease
Aplastic anemia
Agranulocytosis
Leukopenia
Thrombocytopenia
Thrombocytopenic purpura
Melena
Acidosis
Electrolyte imbalance
Muscle weakness
Hematuria
Polyuria
Glycosuria
Hearing dysfunction or tinnitus
Sulfonamide type reactions
Warnings
Contraindications
Hypokalemia
Hyponatremia
Hyperchloremic acidosis
Hypersensitivity to acetazolamide or sulfa
Liver disease
Severe renal disease or dysfunction
Long term use in noncongestive angle-closure glaucoma
Cirrhosis
Long-term administration in patients with chronic, noncongestive angle-closure glaucoma
Cautions
Use caution in COPD, emphysema, and concomitant high-dose aspirin
Use caution in diabetes, respiratory acidosis, and hepatic impairment
Adverse drug reactions common to sulfonamide derivatives; Stevens-Johnson syndrome and toxic epidermal necrolysis (TEN) may occur
May impair alertness and/or physical coordination
FDA-approved product labeling for many medications have included a broad contraindication in patients with a prior allregic reaction to sulfonamides; however, recent studies have suggested that crossreactivity between antibiotic sulfonamides and nonantibiotic sulfonamides is unlikely to occur
May impair alertness and/or physical coordination
Severe adverse effects including tachypnea, anorexia, coma, lethargy, and death reported with high-dose aspirin; use caution or avoid administration
Increasing dose does not increase diuresis; may instead increase the incidence of paresthesia and/or drowsiness
IM administration not recommended due to alkaline pH, which may cause pain
Pregnancy and lactation
Pregnancy category: C
Lactation: Enters breast milk; not recommended
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Diamox Sequels (acetazolamide)
Mechanism of action
Carbonic anhydrase inhibitor that decreases rate of aqueous humor formation, in that way decreasing intraocular pressure
Inhibits H+ ion excretion in renal tubule, increasing sodium, potassium, bicarbonate, and water excretion and producing alkaline diuresis
Inhibits carbonic anhydrase in CNS, which in turn decreases abnormal and excessive discharge from the CNS neurons
Absorption
Bioavailability: Rapidly absorbed orally
Tablet
- Onset: 1-1.5 hr
- Duration: 8-12 hr
- Peak plasma time: 1-4 hr
Sustained-release
- Onset: 2 hr
- Duration: 18-24 hr
- Peak plasma time: 8-18 hr
IV
- Onset: 5-10 min
- Duration: 4-5 hr
- Peak plasma time: 15 min
Distribution
Protein bound: 70-90%
Vd: 0.2 L/kg
Metabolism
Metabolism: None
Elimination
Half-life: 2-4 hr (tablet)
Dialyzable: Yes (hemodialysis)
Excretion: Urine 90%
Administration
IV Incompatibilities
Additive: Multivitamins
Y-site: Diltiazem(?), multivitamins
IV Compatibilities
Solution: Compatible with most common solvents
Additive: Cimetidine, ranitidine
IV Preparation
Standard diluent: 500 mg/50 mL D5W
Minimum volume: 50 mL D5W
IV Administration
IV push: 100-500 mg/min
Infusion: 4-8 hr
Storage
Store intact vials at room temperature
May store reconstituted solution in refrigerator for 3 days or at room temperature for 12 hr