The use of iodine as a germicidal agent is well known. Iodine as such or in various molecular combinations has been used medicinally since soon after its discovery. Iodine was used to treat battle wounds as early as 1839. In various forms, iodine is an outstanding germicide for the skin, for wounds both internal and external, and for sterilization purposes including such things as surgical instruments. It has also been used to disinfect drinking water, swimming pools, and the like, and to sanitize utensils and other objects which might come in contact with organic material subject to decay and bacterial attack.
Iodine is an outstanding therapeutic agent which is useful against a great variety of organisms including viruses, bacteria, spores, yeast, molds, protozoa, fungi, worms, nematodes, and the like. In addition, iodine has a relatively low tissue toxicity. The relatively low toxicity is due to the breakdown of iodine to the iodide ion (I.sub.2 .fwdarw. I-); the iodide ion is non-toxic.
Iodine, however, does have some serious drawbacks. It is a strong primary irritant and a sensitizer. Furthermore, while it destroys bacterial protein, it also, to some extent, destroys animal protein as well. Additionally, iodine has undesirable odor and staining properties.
It has been discovered that certain compounds act as carriers or "taming" agents for iodine. The term "iodophor" is used to refer to any product in which surface active agents act as carriers and solubilizing agents for iodine. Known carriers include a variety of high molecular weight materials such as starch and various synthetic polymers. Typical synthetic polymers are exemplified by polymeric vinyl lactams and high molecular weight oxyalkaline derivatives of reactive hydrogen compounds generally characterized as the alkaline oxide condensates having surface active properties. Specific examples of suitable polymeric material include polyvinyl pyrrolidone, polyvinyl oxizolidone, polyvinyl imidazole, polyvinyl morpholone, polyvinyl caprolactam, polyvinyl alcohol, and ethylene and propylene oxide condensates with alcohols, amides and phenols.
Iodophors generally enhance the bactericidal activity of the iodine while reducing vapor pressure and odor. In addition, iodophors decrease staining properties and permit wide dilutions with water. Additionally, the irritant properties of iodine are markedly reduced when employed in the form of an iodophor.
A particularly useful iodophor composition results from the interaction between iodine, potassium iodide, and polyvinyl alcohol in a water solution. Such a composition is disclosed in Mokhnach, "Iodine-High Polymers and Their Use in Medicine and Veterinary Medicine", (Boton. Inst. im. Komarova, Leningrad) Iodinol Med. Vet. Eksp. Klin. Issled. Akad. Nauk S.S.S.R. Bot. Inst., 1967, 5-20 (Russ.). This composition has been used to treat purulent surgical diseases, varicose ulcers, thermic and chemical burns, and in veterinary practice to treat a wide variety of diseases in animals. It is an effective antiseptic, equally effective with respect to gram positive and gram negative microflora, viruses and fungi. The chemotherapeutical index, i.e., ratio of maximum endurable dose to the medicinal dose of this composition is very large. While these iodophors are very effective, they are not as stable as is desired, i.e., they have a somewhat limited shelf life.
Copending U.S. Application Ser. No. 315,793, Dec. 18, 1972, now U.S. Pat. No. 3,911,107, discloses aqueous solutions prepared from iodine, a water soluble iodide salt, boric acid, and polyvinyl alcohol, which are particularly useful in connection with the present invention. The iodophors of the copending application have a long shelf life coupled with a broad range of germicidal, fungicidal, virucidal, and sanitizing properties. These iodophor solutions, which may be in the form of concentrates or dilute free iodine releasing solutions, may be used for cleaning, sanitizing and disinfecting inanimate as well as animate objects.
For many uses, controlled dissipation of the available iodide in iodophor solutions is not a prerequisite for achieving sterility, tissue tolerance, and ultimate safety. However, there are instances where total destruction of the available iodine (I.sub.2) is desirable either while the iodophor is acting or after the iodophor has acted.
Basically, all compounds commonly known as antioxidants having the appropriate redox potential to convert I.sub.2 to 2I- could be used to destroy available iodine. Examples of such compounds would include alcohols, aldehydes, alkenes, alkynes, aromatic hydrocarbons, amides, quinones, hydroxy acids, sugars, amino acids, sulfites, thiosulfates, sulfhydryl containing compounds, and polyunsaturated organics.
Solutions of such compounds have been found to destroy all of the available iodine at different rates. Many such compounds will be satisfactory for various industrial purposes. However, safety and tissue tolerance requirements restrict the number of compounds suitable for human and animal use.
Compounds suitable for human and animal use include sodium sulfite, sodium thiosulfate, sodium hydrogen sulfite, cysteine, methionine, ascorbic acid, sorbic acid and disodium edetate. Almost immediate inactivation of available iodine in iodophors takes place upon treatment with greater than molar equivalents of inorganic sulfites and thiosulfates, methionine, cysteine and ascorbic acid. This virtually instant neutralization may be desirable in some instances. Where maintenance of sterility of the treatment system is not required, neturalization can be accomplished quite readily with such compounds.
In other instances, a slow but predictable rate of iodine dissipation is more desirable. Additionally, maintenance of sterility after treatment may be required with certain prostheses, e.g., contact lenses stored in a storage case. Under such circumstances, it is necessary that the iodine dissipating solution be sterile and have resterilizing capability as well. Thus, an ideal iodine dissipating agent must be able to not only dissipate iodine, but also must act as an anti-microbial preservative, and have good tissue tolerance properties.
The aqueous solutions of the present invention are extremely well suited for dissipating, at a controlled rate, available iodine contained in iodophor solutions. The solutions are sterile, possess good tissue tolerance properties, and act as an anti-microbial preservative. In addition, the solutions of the present invention are useful as contact lens rinsing and boiling solutions and as eye irrigating solutions.
The aqueous solutions of the present invention are particularly useful in connection with techniques for sterilizing prosthetic and diagnostic devices, particularly contact lenses. Admixtures of the dissipating solution of the present invention with an iodophor solution provide solutions which are effective to maintain the sterility of the treated devices over extended periods of time.