Halazone (BA1377): Atomic Facts on a Sulfonamide Water Disinfection Agent

Executive Summary: Halazone (4-(N,N-dichlorosulfamoyl)benzoic acid, CAS 80-13-7) is a broad-spectrum organic chloramine bactericidal disinfectant used for water disinfection and as a research tool in neurophysiology [APExBIO]. It acts by releasing hypochlorous acid (HOCl), which rapidly targets bacterial cell membranes, achieving complete Escherichia coli kill at ≥1.0 mg/L within 3 minutes under defined conditions [ref]. In neuronal research, Halazone inhibits sodium current inactivation in myelinated frog nerve fibers via membrane lipid modification [Rack et al., 1986]. Animal studies confirm oral doses up to 200 mg/day in rabbits are non-toxic, and the compound is stable in dry formulations at room temperature for up to 150 days [APExBIO]. Halazone is insoluble in water but dissolves in DMSO (≥45.9 mg/mL) and ethanol (≥8.56 mg/mL, ultrasonic assistance).

Biological Rationale

Halazone is an antimicrobial sulfonamide derivative, historically deployed as a chemical water disinfection agent for field and emergency use [APExBIO]. Its broad-spectrum activity arises from its status as an organic chloramine, enabling oxidative bactericidal action. The compound is also a modulator of neuronal sodium channels, making it relevant for neurophysiology and membrane biophysics. Halazone’s dual functionality addresses both environmental pathogen control and fundamental ion channel research [Halazone: Mechanistic Versatility]. Unlike simple chlorine donors, it is stable in solid form and offers controlled release of HOCl, minimizing by-product formation and providing reproducible experimental outcomes.

Mechanism of Action of Halazone

Halazone’s primary disinfection mechanism involves the release of hypochlorous acid (HOCl) upon hydrolysis. HOCl is a potent oxidant that disrupts bacterial cell membranes and metabolic systems, resulting in rapid bactericidal activity [Halazone: Antimicrobial Sulfonamide]. At the molecular level, HOCl oxidizes thiol and amino groups in membrane and cytoplasmic proteins, destabilizing cellular integrity. In neurophysiological contexts, Halazone modulates sodium channel function by inhibiting sodium current inactivation. This effect is hypothesized to occur via oxidative modification of double bonds in phospholipid membrane structures rather than direct protein side-chain modification, as evidenced in frog sciatic nerve fibers under voltage clamp [Rack et al., 1986]. This distinguishes it mechanistically from agents targeting specific amino acid residues.

Evidence & Benchmarks

• At ≥1.0 mg/L Halazone (equivalent to ≥1.0 mg Cl⁻/L), complete Escherichia coli kill is achieved within 3 minutes at redox potential >455 mV (pH 7.0, 20°C) [Atomic Facts on a Sulfonamide Water Disinfectant].
• Halazone inhibits sodium current inactivation in myelinated frog nerve fibers at 5 mM concentration (pH 7.2, 10 min exposure), with effects resembling those of chloramine T and HOCl [Rack et al., 1986].
• Oral administration of 100–200 mg/day in rabbits is non-toxic over standard test durations; a single 500 mg oral dose produces no significant adverse effects [APExBIO].
• Stable in dry formulation with borax or sodium carbonate, Halazone exhibits <7% decomposition at room temperature after 150 days; decomposition accelerates above 40–50°C [APExBIO].
• After oral dosing, about 60% of Halazone is recovered as p-sulfonamidobenzoic acid in urine [APExBIO].
• Solubility: ≥45.9 mg/mL in DMSO, ≥8.56 mg/mL in ethanol (with ultrasonic assistance), insoluble in water [APExBIO].
• For drinking water disinfection, 4 mg Halazone per liter is effective; one 0.004 g tablet disinfects ~0.95 L (1 quart) [APExBIO].

This article extends the quantitative application details and neurophysiological context beyond prior summaries such as Halazone (BA1377): Antimicrobial Sulfonamide Derivative for Waterborne Pathogen Control by providing precise units, experimental conditions, and stability data.

Applications, Limits & Misconceptions

Halazone is validated as a water disinfection agent and an experimental reagent for sodium channel modulation studies. Its utility spans environmental microbiology, neurophysiology, and translational research settings [Halazone: Next-Generation Sulfonamide]. Notably, Halazone's action is rapid, making it ideal for point-of-use water sterilization and short-duration in vitro experiments.

Common Pitfalls or Misconceptions

• Not effective in organic-rich or highly turbid water: Halazone's efficacy is reduced by high organic loads or suspended solids, which consume available chlorine before microbial targets are reached.
• Not a substitute for long-term water storage: Due to instability in aqueous solution, Halazone should be used for immediate or short-term disinfection; do not store solutions for extended periods [APExBIO].
• Not a systemic antibiotic: Halazone is not intended for systemic infection treatment; its pharmacokinetics and metabolism limit its use to local or environmental applications.
• Not universally effective against all protozoa or viruses: While potent against bacteria, efficacy against certain protozoa (e.g., Cryptosporidium) and viruses is not guaranteed at standard doses.
• Not stable at elevated temperatures: Storage above 40–50°C accelerates decomposition; always store under recommended conditions [APExBIO].

Workflow Integration & Parameters

Water Disinfection: Prepare Halazone at 0.4–1.0 mg/L for in vitro antibacterial testing, ensuring effective chlorine concentration ≥1.0 mg/L. For field or clinical use, dissolve 4 mg Halazone per 1 L drinking water. Use only freshly prepared solutions; discard after use [APExBIO].
Neurophysiological Research: Apply 5 mM Halazone in buffered saline (pH 7.2) for 10 minutes to voltage-clamped myelinated frog nerve fibers for sodium channel inactivation studies. Maintain temperature and pH as specified in published protocols [Rack et al., 1986].
Handling and Storage: Store Halazone as a solid, tightly sealed and desiccated at 4°C. Do not attempt long-term storage of prepared solutions. For solubilization, use DMSO or ethanol (ultrasonic assistance recommended for ethanol).

For further technical guidance, the Halazone (BA1377) kit from APExBIO provides research-grade material with validated purity and stability data. This article clarifies practical integration parameters beyond the mechanistic focus in Halazone: Mechanistic Versatility and Strategic Leverage.

Conclusion & Outlook

Halazone (BA1377) is a rigorously characterized, dual-action sulfonamide compound serving as both an antimicrobial agent for water disinfection and a tool compound for sodium channel research. Its oxidative bactericidal mechanism, rapid action profile, and defined stability make it suitable for controlled laboratory and field applications. While limitations exist in terms of protozoal/viral efficacy and solution stability, Halazone remains a cornerstone in waterborne pathogen control and neurophysiological research. For further mechanistic and translational context, see Halazone: Next-Generation Sulfonamide for Waterborne Pathogen Control, which this article updates with atomic, quantitative benchmarks.