Ethoxzolamide binds to and inhibits carbonic anhydrase I and other carbonic anhydrase isoforms. Carbonic anhydrase plays an essential role in facilitating the transport of carbon dioxide and protons across biological membranes. By inhibiting carbonic anhydrase in the proximal renal tubules, ethoxzolamide decreases the reabsorption of water, sodium, potassium, and bicarbonate, leading to diuresis. This mechanism also underlies its ability to reduce intraocular pressure in glaucoma.

Infected macrophages treated with ethoxzolamide (ETZ) showed >90% quantification of reporter GFP fluorescence. Moreover, treatment with ethoxzolamide (ETZ) dramatically slowed the increase of M's intracellular expression. TB in a 9-day transient macrophage test [2].
In vitro, ethoxzolamide potently inhibits carbonic anhydrase activity. It effectively suppresses the carbonic anhydrase activity of photosystem 2 membranes and PS1 membranes. Its activity is typically assessed by measuring the rate of CO₂ hydration or the hydrolysis of p-nitrophenyl acetate in the presence of varying concentrations of the inhibitor.

It was discovered that the body converted fat-soluble ethoxazolamide into dissolved lysates while keeping high enzyme activity. The IOP decreased by 4.2 mmHg, the concentration in the anterior uvea was 2.5 pmol/kg, and the fractional inhibition of enzyme (i) was 0.9995 at the lowest dose that produced the greatest effect (4 mg/kg iv over 45 minutes). The drug's short half-life in the rose membrane causes a slow release of the drug in the anterior uvea and other tissues, which results in a rapid decrease in effect. In mouse lungs, ethoxzolamide (ETZ) strongly captures GFP reporter fluorescence; in comparison to the ratio of mock-treated controls, the GFP signal was inhibited three times. mice's heart tissue after ETZ treatment in comparison to mock-treated controls1]. There is a notable decrease in the rate [2].
Ethoxzolamide is used in vivo as a diuretic and antiglaucoma agent. It is administered orally to reduce intraocular pressure in patients with glaucoma and to promote diuresis in edematous conditions. Its effects are mediated by the inhibition of carbonic anhydrase in the eye and kidney.

Non-cellular enzyme assays for ethoxzolamide involve assessing its inhibition of carbonic anhydrase activity using purified enzyme preparations. The enzyme is incubated with a substrate (e.g., p-nitrophenyl acetate) in the presence of varying concentrations of ethoxzolamide. The rate of substrate hydrolysis is measured spectrophotometrically. IC₅₀ values for carbonic anhydrase inhibition are determined from dose-response curves.

In vitro cellular assays for ethoxzolamide are not standard, as its activity is primarily enzymatic. Its effects on cells can be studied by measuring intracellular pH or bicarbonate transport in cells expressing carbonic anhydrase. The compound's ability to inhibit CO₂ uptake and HCO₃⁻ transport can be assessed in cyanobacterial or mammalian cell models.

In vivo animal experiments with ethoxzolamide are conducted in animal models of glaucoma or edema. The compound is administered to animals, and its effects on intraocular pressure (glaucoma models) or urine output (diuretic models) are measured. Pharmacokinetic studies are also conducted to characterize its absorption, distribution, and elimination.

Absorption, Distribution and Excretion
Absorbed rapidly, with a bioavailability of up to 65%. Absorbed via the gastrointestinal tract…distributed to plasma, muscle, brain, kidneys, liver, lungs, erythrocytes, aqueous humor, and cerebrospinal fluid. Approximately 40%…excreted unchanged by the kidneys per person, oral administration/hr. Biological Half-Life 2.5–5.5 hours.
Ethoxzolamide has a molecular weight of 258.31 and a molecular formula of C₉H₁₀N₂O₃S₂. It is a white to off-white crystalline powder with a purity of ≥98%. The compound is soluble in organic solvents and is typically stored at room temperature in a dry, dark place. It is well absorbed after oral administration.

Protein Binding
~89% Interactions Patients receiving digitalis glycosides may be susceptible to digitalis toxicity due to hypokalemia, which can lead to fatal arrhythmias… Diuretics, corticosteroids, adrenocorticotropic hormone, and amphotericin B/concomitant use with carbonic anhydrase inhibitors may cause severe hypokalemia/ Carbonic anhydrase inhibitors can enhance the effects of other diuretics (such as thiazide diuretics)…/help/enhance and restore the response to mercury diuretics… Rarely, this drug may interfere with the hypoglycemic response of insulin or oral hypoglycemic agents, possibly by causing hypokalemia. Urine alkalization caused by this drug increases the excretion rate of weak acids (including phenobarbital and salicylates)… Methylamine, hippuric methylamine, and mandelic acid methylamine… may be ineffective in the alkaline urine produced by carbonic anhydrase inhibitors. Carbonic anhydrase inhibitors increase lithium excretion… Urine alkalization caused by this drug may decrease the excretion rate of lithium. Tricyclic antidepressants such as amphetamine, procainamide, and quinidine, and their effects may be enhanced and/or prolonged.
Ethoxzolamide is generally well-tolerated, but it can cause side effects related to its diuretic activity, including electrolyte imbalances (hypokalemia), metabolic acidosis, and gastrointestinal disturbances. It is contraindicated in patients with severe renal or hepatic impairment. Standard safety precautions should be followed.

[1]. Relations among IOP reduction, ocular disposition and pharmacology of the carbonic anhydrase inhibitor ethoxzolamide. Exp Eye Res. 1992 Jul;55(1):73-9.

[2]. The Carbonic Anhydrase Inhibitor Ethoxzolamide Inhibits theMycobacterium tuberculosis PhoPR Regulon and Esx-1 Secretion and Attenuates Virulence. Antimicrob Agents Chemother. 2015 Aug; 59(8): 4436–4445.

[3]. Development and validation of an UPLC-MS/MS method for the quantification of ethoxzolamide in plasma and bioequivalent buffers: Applications to absorption, brain distribution, and pharmacokinetic studies. J Chromatogr B Analyt Technol Biomed Life Sci. 2015 Apr 1; 0: 54–59.

Ethoxyzolamide is a sulfonamide drug with the chemical name 1,3-benzothiazole-2-sulfonamide, substituted with an ethoxy group at the 6-position. It is a carbonic anhydrase inhibitor, formerly used to treat glaucoma, and also used as a diuretic. Ethoxyzolamide has multiple pharmacological effects, including as a carbonic anhydrase inhibitor (EC 4.2.1.1), a diuretic, and an anti-glaucoma drug. It belongs to the benzothiazole, sulfonamide, and aromatic ether class of compounds. Ethoxyzolamide is a sulfonamide drug used as a diuretic and for the treatment of glaucoma. It reduces the reabsorption of water, sodium, potassium, and bicarbonate by inhibiting carbonic anhydrase activity in the proximal renal tubules. Its pharmacological activity therefore carries the risk of hypokalemia. Ethoxyzolamide is a sulfonamide and carbonic anhydrase (CA) inhibitor with diuretic and anti-glaucoma effects. In the eye, ethoxyzolamide inhibits carbonic anhydrase, thereby reducing aqueous humor secretion. This may help lower intraocular pressure. In addition, this drug can prevent the reabsorption of bicarbonate and sodium in the proximal renal tubules, thus producing a mild diuretic effect. Ethoxyzoline is a carbonic anhydrase inhibitor and is used as a diuretic and to treat glaucoma. It may cause hypokalemia.

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Drug Indications
Used to treat duodenal ulcers, as a diuretic, to treat glaucoma, and also to treat epilepsy-related seizures.

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Mechanism of Action
Ethoxyzoline binds to and inhibits the activity of carbonic anhydrase I, which plays a crucial role in promoting the transport of CO2 and H+ within cells, across biological membranes, and in the extracellular space. Inhibition of this enzyme can affect the balance of related membrane homeostasis systems.
The primary pharmacological action is the inhibition of carbonic anhydrase. Studies of purified enzymes have shown that this inhibition is non-competitive.
Of course, non-catalytic hydration or dehydration reactions can also occur in the absence of the enzyme.
Carbonic anhydrase inhibitors…reduce the concentration of hydrogen ions that can be exchanged with sodium and potassium ions and combine with bicarbonate to form carbonic acid. /Carbonic anhydrase inhibitors/
…The effect of carbonic anhydrase inhibitors on intraocular pressure is independent of diuresis. They reduce water production…thus lowering pressure. /Carbonic anhydrase inhibitors/

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Therapeutic Uses
Carbonic anhydrase inhibitors; diuretics
.../Uses/Adjunctive therapy for chronic simple (open-angle) glaucoma, secondary glaucoma, and preoperative reduction of intraocular pressure in acute angle-closure glaucoma.
Effective doses appear to be between 125 and 1000 mg/day, orally in divided doses.
Veterinary use: For the treatment of mild congestive cardiac edema.
For more complete data on the therapeutic uses of ethoxyzolam (6 types), please visit the HSDB record page.

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Drug Warnings
...Carbonic anhydrase inhibitors should be used with caution in patients with obstructive pulmonary disease, as they may induce acute respiratory failure. Carbonic anhydrase inhibitors may have teratogenic effects and should therefore be avoided during early pregnancy. Carbonic anhydrase inhibitors are also used for preoperative treatment of acute angle-closure glaucoma and congenital glaucoma. …More than 50% of patients… must discontinue treatment due to adverse reactions. Osmotic agents are used to rapidly reduce intraocular pressure and vitreous volume before iridectomy and other ophthalmic surgeries. /Carbonic Anhydrase Inhibitors/
Renal colic, hematuria, oliguria, or anuria may occur during long-term treatment…Carbonic anhydrase inhibitors reduce uric acid excretion and increase serum uric acid levels. …Hyperuricemia is usually asymptomatic but rarely causes exacerbation of gout. /Carbonic Anhydrase Inhibitors/
For more complete data on drug warnings for ethoxyzolam (7 of 7), please visit the HSDB record page.

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Pharmacodynamics
Ethoxyzolam is a proximal tubular carbonic anhydrase inhibitor whose mechanism of action is by reducing the reabsorption of water, sodium, potassium, and bicarbonate. It can also reduce the activity of carbonic anhydrase expressed in the central nervous system, thereby increasing the seizure threshold. Inhibiting ocular carbonic anhydrase helps it lower intraocular pressure and reduce aqueous humor.
Ethoxzolamide (CAS 452-35-7) is a potent and specific carbonic anhydrase inhibitor. It is used as a diuretic and in the treatment of glaucoma. By inhibiting carbonic anhydrase, it reduces bicarbonate reabsorption and fluid retention. Ethoxzolamide is a valuable research tool for studying carbonic anhydrase function and pharmacology.

C9H10N2O3S2

258.3173

258.013

452-35-7

3295

White to off-white solid powder

1.47g/cm3

464.9ºC at 760mmHg

190-193ºC(lit.)

235ºC

8.05E-09mmHg at 25°C

1.644

3.123

1

6

3

16

341

0

OUZWUKMCLIBBOG-UHFFFAOYSA-N

InChI=1S/C9H10N2O3S2/c1-2-14-6-3-4-7-8(5-6)15-9(11-7)16(10,12)13/h3-5H,2H2,1H3,(H2,10,12,13)

6-ethoxy-1,3-benzothiazole-2-sulfonamide

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ≥ 100 mg/mL (~387.12 mM)
H2O : ~1 mg/mL (~3.87 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (8.05 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (8.05 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (8.05 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)