Wang L, PhD, ^a Bassiri M, PhD, ^a Najafi R, PhD, ^a Najafi K, MD, ^b Yang J, BS, ^a Khosrovi B, PhD, ^a Hwong W, BS, ^a Barati E, BS, ^a Belisle B, PhD, ^a Celeri C, MS^a , and Robson MC, MD ^c

^aNovaBay Pharmaceuticals, Inc, Emeryville, CA; ^bEye Institute San Rafael, CA; and ^c Institute for  Tissue Regeneration, Repair and Rehabilitation, Bay Pines, FL.

Objective: Hypochlorous acid (HOCl), a major inorganic bactericidal compound of innate immunity, is effective against a broad range of microorganisms. Owing to its chemical nature, HOCl has never been used as a pharmaceutical drug for treating infection. In this article, we describe the chemical production, stabilization, and biological activity of a pharmaceutically useful formulation of HOCl. Methods: Stabilized HOCl is in the form of a physiologically balanced solution in 0.9% saline at a pH range of 3.5 to 4.0. Chlorine species distribution in solution is a function of pH. In aqueous solution, HOCl is the predominant species at the pH range of 3 to 6. At pH values less than 3.5, the solution exists as a mixture of chlorine in aqueous phase, chlorine gas, trichloride (Cl− 3 ), and HOCl. At pH greater than 5.5, sodium hypochlorite (NaOCl) starts to form and becomes the predominant species in the alkaline pH. To maintain HOCl solution in a stable form, maximize its antimicrobial activities, and minimize undesirable side products, the pH must be maintained at 3.5 to 5. Results: Using this stabilized form of HOCl, the potent antimicrobial activities of HOCl are demonstrated against a wide range of microorganisms. The in vitro cytotoxicity profile in L929 cells and the in vivo safety profile of HOCl in various animal models are described. Conclusion: On the basis of the antimicrobial activity and the lack of animal toxicity, it is predicted that stabilized HOCl has potential pharmaceutical applications in the control of soft tissue infection.