Hypochlorous acid (HOCl) is a weak acid long known for its potent oxidizing and bactericidal properties. In vivo, it is a vital component of the immune system, produced by phagocytes such as neutrophils during the respiratory burst to kill invading pathogens. This endogenous property endows hypochlorous acid with excellent biocompatibility. In recent years, major breakthroughs in production technology have enabled the commercial mass production of high-purity, highly stable hypochlorous acid solutions, rapidly expanding its application areas.
The key role of hypochlorous acid in pharmaceutical production
The application of hypochlorous acid in pharmaceutical production has gone beyond the scope of traditional disinfectants. It is not only a key tool for ensuring drug quality and the sterility of the production environment, but its potential in the field of chemical synthesis is also gradually being discovered.
1.1 Environmental control and efficient disinfection
Maintaining a sterile or low-microbial-burden production environment is a cornerstone of pharmaceutical manufacturing, particularly biopharmaceuticals and sterile dosage forms. Hypochlorous acid, with its high efficacy, broad spectrum, safety, and environmental friendliness, has become an ideal disinfectant choice in this field.
· Core application scenarios:
· Cleanroom Disinfection: Hypochlorous acid can be used to disinfect the air and surfaces of pharmaceutical cleanrooms, effectively killing both suspended and attached microorganisms. Recent technological innovations, such as the spraying of hypochlorous acid in nano-aerosol form, have significantly increased diffusion speed and disinfection efficiency while also reducing the amount of stock solution used.
· Equipment and System Disinfection: Hypochlorous acid is widely used for surface disinfection of production equipment, cold sterilization of instruments and meters, and terminal disinfection of CIP (clean-in-place) systems. Its powerful oxidizing ability effectively removes and prevents the growth of even the most stubborn biofilms in piping systems, which is crucial for maintaining the microbiological quality of water systems and fluid pipelines.
· Performance advantages:
· Highly Effective Sterilization: Research has confirmed that hypochlorous acid is 80 to 100 times more effective at killing bacteria than sodium hypochlorite (the main component of bleach), a traditional chlorine-based disinfectant. It can quickly penetrate microbial cell membranes and walls, destroying key biomolecules like proteins and nucleic acids. It acts quickly and is less likely to induce drug resistance.
· High safety: Identical to the bactericidal substances produced by the human immune system, high-purity hypochlorous acid solution is non-toxic or extremely low-toxic to human cells, non-irritating to the skin and mucous membranes, and decomposes into water and trace salts after action, leaving no harmful residue.
· Environmental friendliness: Its environmentally friendly characteristics are in line with the current trend of green production in the pharmaceutical industry.
1.2 Innovation in production technology and patent progress
The popularization of hypochlorous acid applications is inseparable from the revolutionary progress in its production technology.
· From unstable to highly pure and stable: Early hypochlorous acid production methods (such as mixing hydrochloric acid with sodium hypochlorite) produced solutions that not only contained impurities like chlorine, but also exhibited extremely unstable chemical properties and a short shelf life, limiting their large-scale application. Modern, advanced electrochemical activation (ECA) technology, through the electrolysis of low-concentration brine, enables the large-scale production of hypochlorous acid solutions with stable pH, high purity, and a shelf life of over a year under precisely controlled conditions.
· Localized Production and Patent Development: Modular, small-scale, on-site hypochlorous acid production equipment has become feasible, enabling pharmaceutical companies to produce on-demand, reducing transportation and storage costs for disinfectants while increasing accessibility to factories in remote areas. Between 2023 and 2025, several new patents related to the production, storage, and application of hypochlorous acid emerged, such as for anti-evaporation storage devices and integrated production and storage equipment, demonstrating the continued vitality of technological innovation in this field.
1.3 Potential as a synthetic reagent and industrial application
In addition to being an auxiliary material, hypochlorous acid also plays a direct role in the chemical synthesis of active pharmaceutical ingredients (APIs).
· Chlorohydrination: One of the most well-known applications of hypochlorous acid in organic synthesis is as an electrophilic reagent, reacting with alkenes to form chlorohydrins. Chlorohydrins are a very important class of organic synthesis intermediates.
· Industrial case related:
· Chlorohydrins are key precursors for the industrial synthesis of epichlorohydrin (ECH). Epichlorohydrin is a widely used chemical raw material used in the synthesis of various APIs. For example, epichlorohydrin is a key cross-linking agent in the production of the cholesterol-lowering drug colestipol hydrochloride.
· Despite the clear synthetic route, detailed industrial case studies, including specific process parameters (e.g., temperature, pressure, reaction time), and yield data for the direct commercialization of hypochlorous acid-mediated chlorohydrin synthesis for API production since 2023, remain limited in the published literature (Query: Industrial process parameters and yield data..., Query: Industrial case studies of hypochlorous acid-mediated chlorohydrin synthesis...). Existing industrial data primarily focuses on the production of bulk chemicals like epichlorohydrin. For example, the synthesis of propylene chlorohydrin has been described as operating at 35–50 °C and 2–3 bar pressure.
· Mechanistic Research Progress: Recent theoretical calculations (2023) have delved into the complex mechanism of the reaction between hypochlorous acid and alkenes, demonstrating that the reaction pathway (synergistic, stepwise, or nucleophilic addition) depends on the electronic effects of the olefin substrate. This provides theoretical guidance for optimizing reaction conditions and improving selectivity. With a deeper understanding of the reaction mechanism and the application of green synthesis techniques such as continuous flow chemistry, hypochlorous acid, as an efficient and atom-economical chlorination and oxidation reagent, has great potential in the future synthesis of complex pharmaceutical molecules.
Hypochlorous acid as a therapeutic agent and pharmaceutical active ingredient
Hypochlorous acid is gradually transforming from a "disinfectant" to a "drug" active ingredient recognized by regulatory agencies and with clear therapeutic effects, and has made significant progress in the fields of wound care and anti-infection.
2.1 Regulatory Approval and Market Status
Drug regulatory agencies in several countries around the world have opened the door to hypochlorous acid-based medical products.
· The US FDA has approved several topical products containing hypochlorous acid as an active ingredient for the treatment of acute and chronic wounds, burns, ulcers, and various skin infections in humans and pets. The FDA has also approved it for high-level disinfection of medical devices.
· EU and Japan: In the EU, hypochlorous acid products are approved as Class III medical devices; Japan's Ministry of Health, Labour and Welfare has also approved its hypochlorous acid for topical medical applications.
· Examples of marketed products: Several prescription and over-the-counter products with hypochlorous acid or its salts as core ingredients are now available on the market, such as eye care solutions for treating blepharitis and Sebuderm gel, which uses sodium hypochlorite as its active ingredient and is used to treat seborrheic dermatitis.
2.2 Application for inclusion in the World Health Organization (WHO) Essential Medicines List
A landmark event elevating hypochlorous acid to the level of a global public health strategy was its formal proposal for inclusion on the WHO Essential Medicines List (EML) in 2025. This proposal, which includes it in the disinfection, antiseptic, and wound care categories, is supported by solid clinical evidence.
· Quantitative clinical efficacy evidence:
· Excellent wound healing rate: Multiple randomized controlled trials (RCTs) have shown that hypochlorous acid performs excellently in wound healing.
· Compared to conventional treatments: Hypochlorous acid has demonstrated significant advantages over the widely used povidone-iodine in promoting granulation tissue formation, reducing wound area, and alleviating pain and odor. A study of venous leg ulcers showed an average reduction of 70% in wound size in the HOCl group, compared to only 50% in the povidone-iodine group.
· For difficult-to-heal wounds: In the treatment of diabetic foot ulcers (DFUs), one study reported a clinical success rate of 93.3% at day 14 for patients treated with hypochlorous acid alone, compared to 56.3% for conventional therapy. In another study, 90% of hypochlorous acid-treated wounds met criteria for surgical closure within 14 days, compared to 0% in the control group.
· Broad-spectrum and potent antibacterial activity: Hypochlorous acid is not only highly effective in killing common bacteria and fungi in wounds, but studies have also shown that it has a strong inactivation ability against a variety of viruses, including SARS-CoV-2, and even highly resistant prions (such as the pathogen of mad cow disease).
· Reliable safety data:
· Extremely low incidence of adverse events: A voluntary exposure study involving over 450 inhalation exposures to hypochlorous acid mist, included in the dossier supporting the EML application, showed no reports of serious adverse reactions. Only 2.6% of participants reported transient, mild side effects such as nasal tingling.
· Excellent biocompatibility: Numerous in vitro and in vivo studies have confirmed that therapeutic concentrations of hypochlorous acid are non-toxic to human tissue cells and do not inhibit cell proliferation and migration during wound healing. This is in stark contrast to the cytotoxicity of many traditional disinfectants (such as high-concentration hydrogen peroxide and povidone-iodine).
2.3 Exploration of emerging therapeutic areas
The therapeutic potential of hypochlorous acid is expanding into more areas. Preliminary studies have shown its potential in treating inflammatory diseases such as allergic conjunctivitis and atopic dermatitis. More interestingly, a cutting-edge study has shown that using hypochlorous acid to oxidize tumor lysates can enhance the immunogenicity of mRNA tumor antigens, suggesting a potential new role for hypochlorous acid in the cutting-edge field of tumor immunotherapy.
Research progress of hypochlorous acid-related drug delivery systems
Although there is currently no clear "hypochlorous acid-specific" drug delivery system on the market, based on its unique biochemical properties, the development of such intelligent delivery systems has become an extremely attractive frontier direction in this field.
3.1 Design principles and potential opportunities of stimuli-responsive nanocarriers
Smart drug delivery systems are designed to leverage the unique microenvironment of the lesion (e.g., low pH, high reducing properties, and overexpression of specific enzymes) as a trigger for precise, on-demand drug release. Hypochlorous acid, an endogenous signaling molecule produced in large quantities by immune cells at sites of inflammation and infection, provides a natural target for the design of a novel "oxidative stress-responsive" drug delivery system.
· Potential design ideas: A nanocarrier could be constructed with chemical bonds (such as thioethers and selenoethers) that are highly sensitive to hypochlorous acid. Under normal physiological conditions, the carrier remains stable, protecting the drug within from leakage. However, when the carrier reaches the site of inflammation or infection and encounters high concentrations of hypochlorous acid, the sensitive chemical bonds are rapidly oxidized and broken, causing the carrier structure to disintegrate, thereby rapidly releasing the encapsulated drug (such as an antibiotic or anti-inflammatory drug) (based on chemical reasoning).
· Technical Foundation: Currently, various nanocarrier technologies, including polymer micelles, liposomes, hydrogels, and polymer-lipid hybrid nanoparticles (LPHNPs), are quite mature. These platforms can all be chemically modified to introduce responsive groups.
3.2 Nanocarrier Patent Technology Trends 2023-2025
Although there are no patents directly targeting hypochlorous acid between 2023 and 2025, patents and research trends in the field of nanodrug delivery lay the foundation for the future development of hypochlorous acid-responsive systems.
· Polymer matrix composition: Research focuses on biodegradable materials such as poly(lactic-co-glycolic acid) (PLGA) and innovative polymer-lipid hybrid nanoparticles (LPHNPs), which combine the high biocompatibility of liposomes with the structural stability of polymer particles.
· Surface modification and targeting: Modification on the surface of nanocarriers is the key to achieving precise delivery.
· Prolonged circulation: Polyethylene glycol (PEG) is used for "stealth" modification to avoid clearance by the immune system and prolong circulation time in the blood.
· Active targeting: Specific ligands (such as hyaluronic acid, folic acid, and RGD peptides) are covalently attached to the surface of a carrier, enabling it to actively recognize and bind to overexpressed receptors on target cells, achieving a "missile-like" attack. The relevant ligand coupling method is one of the core technologies in this field.
3.3 Future Outlook: From Concept to Reality
The development of a hypochlorous acid-responsive drug delivery system represents a truly intelligent, "physiologically signal-driven" drug delivery model. This system can precisely deliver drugs to where they are most needed and release them when they are most needed, potentially significantly improving efficacy and reducing systemic side effects. This holds great potential for clinical translation, particularly in the treatment of localized infections, chronic inflammation, and certain cancers.
Industry standards and regulatory specifications
With the popularization of hypochlorous acid products, it is crucial to establish and improve relevant quality control standards, which are directly related to the effectiveness and safety of the products.
4.1 National and industry standards related to disinfectants
In China, as a disinfectant product, the production and quality of hypochlorous acid must comply with a series of national and industry standards.
· Core national standard: GB/T 36758-2018 "Hygienic Requirements for Chlorine-Containing Disinfectants" is a programmatic document in this field. It sets clear requirements for the product's raw materials, appearance, pH value, available chlorine content, stability, and microbial killing effect.
· Key technical indicators:
· pH: Standards require a pH range of 4.0-7.0. This is key to ensuring that hypochlorous acid molecules (HOCl) predominate rather than hypochlorite ions (OCl⁻), as the former has far greater bactericidal activity than the latter.
· Available chlorine and hypochlorous acid content: The more targeted group standard T/SDA 001-2022 "Hygiene Requirements for Hypochlorous Acid Disinfectants" further stipulates that the hypochlorous acid content in the product should be greater than 50% of the total available chlorine content to ensure its high efficiency.
· Stability: The standard requires that the content of liquid products must not fall below the lower limit of the labeled value during the shelf life (usually no less than 6 months). This is a core indicator for measuring product quality and production technology level.
· Safety and compatibility: Products must pass multiple toxicology tests, including acute oral toxicity and skin irritation. Furthermore, their corrosiveness and bleaching properties on various materials (e.g., metals and fabrics) must be clearly labeled, as hypochlorous acid is somewhat corrosive to metals like carbon steel, copper, and aluminum.
4.2 Challenges and Considerations in Application
· Stability is the lifeline: Hypochlorous acid is chemically active and easily reacts with organic matter or decomposes under light or high temperature. Therefore, maintaining its stability is the core difficulty of production technology and the key to distinguishing the quality of products.
· Material compatibility: Material compatibility testing must be performed before use on pharmaceutical equipment, especially for precision instruments and non-corrosion-resistant materials.
· Market supervision: Due to technical barriers, product quality varies widely on the market. When choosing a product, users should proactively request authoritative third-party testing reports from the seller to ensure product compliance, effectiveness, and safety.
Conclusion and Outlook
As of August 2025, the role of hypochlorous acid in the pharmaceutical field has undergone a profound evolution. No longer just an obscure disinfectant in production workshops, it is now a rising star in wound care, anti-infection treatment, and even more cutting-edge fields, leveraging solid scientific evidence and technological breakthroughs.
Summary of core findings:
1. The breadth and depth of application go hand in hand: the application of hypochlorous acid has expanded from environmental disinfection to direct clinical treatment, and has shown industrial potential as an API synthesis reagent.
2. Driven by both technology and evidence: Stable commercial production technology is the cornerstone of its application expansion, while a large amount of high-quality clinical trial evidence (especially the evidence supporting its inclusion in the WHO Essential Medicines List) is the key to its recognition by the medical community.
3. Huge potential for the future: In the field of smart drug delivery, although it is still in the conceptual stage, the unique properties of hypochlorous acid as an endogenous trigger signal have opened up an imaginative research and development direction.
Outlook for future trends:
· Regulatory: We believe that as more clinical data accumulates, hypochlorous acid will gain wider global regulatory recognition as a safe and effective therapeutic agent. Its formal inclusion in the WHO Essential Medicines List is highly likely, significantly promoting its widespread use worldwide, particularly in resource-poor settings.
· Technology and R&D level:
· Synthetic chemistry: The number of industrial cases using hypochlorous acid for green and efficient API synthesis is expected to increase, especially when combined with advanced manufacturing technologies such as continuous flow chemistry, its value in the construction of complex molecules will be further explored.
· Drug delivery: Hypochlorous acid-responsive smart drug delivery systems are expected to move from theoretical concepts to laboratory research in the next few years, and the first batch of related patented technologies may be born.
· Therapeutic areas: Its exploration in ophthalmology, dermatology, anti-tumor immunotherapy and other fields will continue to deepen, and it is expected to develop more innovative treatment options.
In summary, hypochlorous acid, leveraging its unique biological and chemical properties, is playing an increasingly important and diverse role in the 21st-century pharmaceutical industry. Its transformation from a basic chemical to a multifunctional pharmaceutical molecule clearly demonstrates the immense value that can be generated by integrating basic scientific research, engineering innovation, and clinical medical needs. Its future development prospects warrant the continued attention and anticipation of the entire pharmaceutical and healthcare industry.
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