Abstract:
A method for preparing an EDTA-Tris composition which comprises the steps of: 
     mixing ethylenediaminetetraacetic acid (EDTA) USP with tris(hydroxymethyl)aminomethane (Tris) USP to provide an EDTA-Tris USP mixture; 
     and buffering the EDTA-Tris USP mixture with a pH adjuster to a pH of between about 7.9 and 8.10.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a complete application of provisional application Serial No. 60/123,070, filed Mar. 3, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is directed toward a method for preparing an EDTA-Tris composition, a composition which contains EDTA-Tris and uses therefor. In particular, a method for preparing a combination of EDTA and Tris in a form suitable for mass marketing is provided. 
     2. Description of the Prior Art 
     Compositions comprising combinations of ethylenediamine-tetraacetic acid (hereinafter “EDTA”) and tromethamine or tris(hydroxymethyl)aminomethane (“tris”) are known. Such compositions (hereinafter “EDTA-Tris compositions”) are useful as antimicrobial agents when used alone or in combination with other antimicrobial agents, e.g., antibiotics. Synergistic activity was observed when EDTA-Tris plus amikacin and EDTA-Tris plus neomycin were tested against  Staphylococcus intermedius, Proteus mirabilis, Pseudomonas aeruginosa  and  Escherichia coli.  Sparks et al, “Antimicrobial effect of combinations of EDTA-Tris and amikacin or neomycin on the microorganisms associated with otitis externa in dogs”,  Vet. Res. Commun.,  1994, Vol. 18 (4), pp. 241-9. 
     However, prior to the present invention, EDTA-Tris solutions were prepared from stock (laboratory grade) solutions which were adjusted to a pH of 8.0 with concentrated HCl or other acids. EDTA and Tris compositions prepared according to United States Pharmacopeia (“USP”) standards were not previously used and EDTA-Tris compositions were not available in a form suitable for mass marketing. 
     It is therefore an object of the present invention to provide an EDTA-Tris composition which is prepared in a form which makes it suitable for mass marketing and which is more readily available to the public. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a method for preparing an EDTA-Tris composition is provided and comprises adding EDTA to tromethamine, both being prepared according to USP standards (hereinafter referred to as “EDTA USP” and “Tris USP”, respectively), and buffering the EDTA-Tris mixture with HCl or other appropriate acid buffer or pH adjuster to a pH of between about 7.9-8.10. 
     According to a second aspect of the present invention, a composition is provided which comprises EDTA USP, Tris USP and an appropriate acid buffer, such as HCl or other pH adjuster. 
     According to a third aspect of the present invention, an article of manufacture is provided comprising an EDTA USP-Tris USP composition and a receptacle containing the EDTA USP-Tris USP composition. 
     According to a fourth aspect of the present invention, a method of preparing the article of manufacture is provided which comprises obtaining EDTA and Tris prepared according to USP standards, grinding EDTA USP and Tris USP with appropriate acid buffer or pH adjuster, and placing the ground ingredients in a receptacle. Distilled water is then added. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     EDTA-Tris compositions need to be buffered to a pH of about 8.0 to make them suitable for use. In order to do so, a PH adjuster or suitable acid buffer such as HCl or sulphuric acid is added. Although any pH adjuster may be used, the use of tris(hydroxymethyl)aminomethane hydrochloride is preferred. The preferred ratio of EDTA:pH adjuster:Tris is approximately 1:1.25:3.875. 
     Although any EDTA in USP form may be used, edetate disodium dihydrate is preferred. 
     As mentioned above, the type of EDTA and Tris used to prepare the EDTA-Tris compositions is that prepared according to USP standards. This makes it possible to provide a form of EDTA-Tris which is more readily available to the public and which can be mass marketed. 
     Although the EDTA-Tris compositions according to the present invention may be made available in a form other than a solid, e.g., a solution, a solid form is preferred. This makes the composition easily dispensable and/or more suitable for dispensing in a receptacle for manufacture wherein distilled water or other suitable solution is subsequently added so as to obtain a solution suitable for administration. Prior to the present invention only solutions of EDTA-Tris had been prepared. 
     An EDTA-Tris solution having a pH of about 7.9-8.10 is obtained by shaking the solution, once the distilled water is added, for about 10 seconds, letting the solution sit for about 2 hours and re-shaking the solution. 
     Examples of receptacles for manufacture include, but are not limited to, bottles, containers, sachets and the like. The instructions for use of the EDTA-Tris composition may be printed on the receptacle. Uses of EDTA-Tris compositions include multi-cleansing solutions, especially in veterinary use to clean animals&#39; ears, and as an alkalinizing and pretreatment solution, in combination with various antimicrobial agents for treatment of bacteria, and in combination with lysozymes for treatment of selected pathogenic bacteria. Of course all uses known in the art for EDTA-Tris compositions are also contemplated for the composition of the present invention. 
     Other organs on which the EDTA-Tris compositions can be effectively used, include but are not limited to, eyes, bladders, teats, nose and sinuses. It is also useful on wounds. 
    
    
     EXAMPLE 1 
     141 mg of edetate disodium dihydrate (EDTA disodium dihydrate) from Sigma Chemical Company, St Louis, Mo. (Product Number E0399) was added to 533 mg of tromethamine (tris(hydroxymethyl)aminomethane) or “Tris” from Sigma Chemical Company (Product Number T6687) and 176 mg of TRIZMA-HCl (tris(hydroxymethyl)aminomethane hydrochloride) also from Sigma Chemical Company (Product Number T6666). The solid mixture was ground and was then added to a bottle. 112 ml of distilled water was added to the bottle. The bottle was shaken for about 10 seconds to dissolve the mixture and the mixture was left to sit for about 2 hours. The pH was tested and was approximately between 7.9 to 8.10. The Tris and EDTA used were both USP grade. 
     EXAMPLE 2 
     The EDTA-Tris solution prepared according to Example 1 was applied to a cotton swab and was administered liberally to the ear of the patient, while firmly massaging the base of the ear. Excess solution was removed with a further cotton swab. Application was repeated as necessary.