Acetazolamide, Acetazolamide Sodium (Diamox, Dazamide)

By | 2013-06-07

Carbonic Anhydrase Inhibitor Diuretic; Antiglaucoma Agent

Highlights Of Prescribing Information

Used primarily for metabolic alkalosis or glaucoma in small animals; HYPP in horses

Contraindicated in patients with significant hepatic, renal, pulmonary or adrenocortical insufficiency, hyponatremia, hypokalemia, hyperchloremic acidosis or electrolyte imbalance

Give oral doses with food if GI upset occurs

Electrolytes & acid/base status should be monitored with chronic or high dose therapy

Monitor with tonometry if using for glaucoma

What Is Acetazolamide Used For?

Acetazolamide has been used principally in veterinary medicine for its effects on aqueous humor production in the treatment of glaucoma, metabolic alkalosis, and for its diuretic action. It may be useful as an adjunctive treatment for syringomyelia in dogs. Acetazolamide’s use in small animals is complicated by a relatively high occurrence of adverse effects.

In horses, acetazolamide is used as an adjunctive treatment for hyperkalemic periodic paralysis (HYPP).

In humans, the drug has been used as adjunctive therapy for epilepsy and for acute high-altitude sickness.

Before you take Acetazolamide

Contraindications / Precautions / Warnings

Carbonic anhydrase inhibitors are contraindicated in patients with significant hepatic disease (may precipitate hepatic coma), renal or adrenocortical insufficiency, hyponatremia, hypokalemia, hyperchloremic acidosis, or electrolyte imbalance. They should not be used in patients with severe pulmonary obstruction that are unable to increase alveolar ventilation or in those who are hypersensitive to them. Long-term use of carbonic anhydrase inhibitors is contraindicated in patients with chronic, noncongestive, angle-closure glaucoma as angle closure may occur and the drug may mask the condition by lowering intraocular pressures.

Acetazolamide should be used with caution in patients with severe respiratory acidosis or having preexisting hematologic abnormalities. Cross sensitivity between acetazolamide and antibacterial sulfonamides may occur.

Adverse Effects

Potential adverse effects that maybe encountered include: GI disturbances, CNS effects (sedation, depression, weakness, excitement, etc.), hematologic effects (bone marrow depression), renal effects (crystalluria, dysuria, renal colic, polyuria), hypokalemia, hypergly-cemia, hyponatremia, hyperuricemia, hepatic insufficiency, derma-tologic effects (rash, etc.), and hypersensitivity reactions.

At the dosages used for HYPP in horses adverse effects are reportedly uncommon.

Overdosage / Acute Toxicity

Information regarding overdosage of this drug was not located. Monitor serum electrolytes, blood gases, volume status, and CNS status during an acute overdose; treat symptomatically and supportively.

How to use Acetazolamide

Directions for reconstitution of injection: Reconstitute 500 mg vial with at least 5 mL of Sterile Water for Injection; use within 24 hours after reconstitution.

Acetazolamide dosage for dogs:

For adjunctive treatment of metabolic alkalosis:

a) 10 mg/kg four times daily (may aggravate volume contraction and hypokalemia) ()

For adjunctive therapy of glaucoma:

a) 10-25 mg/kg divided 2-3 times daily ()

b) 50-75 mg/kg PO 2-3 times a day ()

c) 50 mg/kg IV one time; 7 mg/kg, PO three times daily ()

For adjunctive therapy of hydrocephalus in pediatric patients:

a) 0.1 mg/kg PO q8h ()

Acetazolamide dosage for cats:

For adjunctive therapy of glaucoma:

a) 50 mg/kg IV once; 7 mg/kg, PO three times daily ()

Acetazolamide dosage for horses:

(Note: ARCI UCGFS Class 4 Acetazolamide)

For adjunctive therapy of hyperkalemic periodic paralysis (HYPP):

a) 2.2-4.4 mg/kg PO twice daily ()

b) 0.5-2.2 mg/kg PO twice daily ()

c) 3 mg/kg PO (dosing interval not specified) ()

■ Ruminants:

a) 6-8 mg/kg IV, IM, or SC ()

Acetazolamide dosage for swine:

a) 6-8 mg/kg IV, IM, or SC ()

Monitoring

■ Intraocular pressure tonometry (if used for glaucoma)

■ Blood gases if used for alkalosis

■ Serum electrolytes

■ Baseline CBC with differential and periodic retests if using chronically

■ Other adverse effects

Client Information

■ Give with food if using oral preparation and GI upset occurs

■ Notify veterinarian if abnormal bleeding or bruising occurs or if animal develops tremors or a rash

Chemistry / Synonyms

A carbonic anhydrase inhibitor, acetazolamide occurs as a white to faintly yellowish-white, odorless, crystalline powder with pKas of 7.4 and 9.1. It is very slightly soluble in water, sparingly soluble in hot water (90- 100°C) and alcohol. Acetazolamide sodium occurs as a white lyophilized solid and is freely soluble in water. The injection has a pH of 9.2 after reconstitution with Sterile Water for Injection. Acetazolamide may also known as: acetazolam, acetazolamidum, or sodium acetazolamide; many trade names are available.

Storage / Stability/Compatibility

Acetazolamide products should be stored at room temperature.

To prepare parenteral solution: reconstitute with at least 5 mL of Sterile Water for Injection. After reconstitution, the injection is stable for one week when refrigerated, but as it contains no preservatives, it should be used within 24 hours.

Acetazolamide sodium for injection is reportedly physically compatible with all commonly used IV solutions and cimetidine HC1 for injection.

Dosage Forms / Regulatory Status

Veterinary-Labeled Products: None

The ARCI (Racing Commissioners International) has designated this drug as a class 4 substance. See the appendix for more information.

Human-Labeled Products:

Acetazolamide Tablets: 125 mg, 250 mg; generic; (Rx)

Acetazolamide Sustained-Release Capsules: 500 mg; Diamox Sequels (Barr); (Rx)

Acetazolamide Injection: 500 mg per vial; Diamox (Wyeth-Ayerst); (Rx)

Acetazolamide Powder for Injection (lyophilized): 500 mg for re-constitution; generic; (Rx)