Coating processes – Medical or dental purpose product; parts; subcombinations;... – Implantable permanent prosthesis
Reexamination Certificate
2001-07-10
2003-07-08
Beck, Shrive P. (Department: 3731)
Coating processes
Medical or dental purpose product; parts; subcombinations;...
Implantable permanent prosthesis
C427S002280, C427S002300, C427S002310, C427S002250, C427S336000, C427S348000, C427S372200, C427S430100
Reexamination Certificate
active
06589591
ABSTRACT:
FIELD OF INVENTIONS
The present invention relates to indwelling or implanted medical devices treated with an antimicrobial agent to inhibit the growth of bacterial and fungal organisms. The invention also relates to a method of treating indwelling or implanted medical devices with an antimicrobial agent.
BACKGROUND
Indwelling medical devices such as catheters are becoming essential to patient care. The benefit derived from these catheters, orthopedic devices, and other types of medical implants, however, is often offset by infectious complications.
Some of the common organisms causing infectious complications associated with indwelling medical devices are
Staphylococcus epidermidis
and
Staphylococcus aureus
. In the case of vascular catheters, these two organisms account for almost 70-80% of all infectious organisms, with
Staphylococcus epidermidis
being the most common organism. Gram-negative bacilli cause about 15-20% of the infections, and Candida species, a fungal agent, accounts for about 10-15% of the vascular catheter infections. Other gram-negative bacteria and fungal organisms (Candida) account for the remaining one-third of cases.
Another common hospital-acquired infection is a urinary tract infection (UTI). The majority of UTI cases are associated with the use of urinary catheters, including transurethral foley, suprapubic and nephrostomy catheters. These urinary catheters are inserted in a variety of populations, including the elderly, stroke victims, spinal cord-injured patients, postoperative patients and those with obstructive uropathy. Despite adherence to sterile guidelines for the insertion and maintenance of urinary catheters, catheter-associated UTI continues to pose a major problem. In the U.S. alone, about 1 million cases of hospital-acquired cases of UTI occur annually. For instance, it is estimated that almost one-quarter of hospitalized spinal cord-injured patients develop symptomatic UTI during their hospital course. Gram-negative bacilli account for almost 60-70%, enterococci for about 25% and Canada species for about 10% of cases of UTI.
Colonization of bacteria on the surfaces of the implant or other parts of the device can produce serious patient problems, including the need to remove and/or replace the implanted device and to vigorously treat secondary infective conditions. A considerable amount of attention and study has been directed toward preventing such colonization by the use of antimicrobial agents, such as antibiotics, bound to the surface of the materials employed in such devices. In such attempts, the objective has been to produce a sufficient bacteriostatic or bactericidal action to prevent colonization.
Various methods have previously been employed to prevent infection of medical devices. A simple method is to flush the surfaces of a device with an antimicrobial solution. Generally, this flushing technique requires convenient access to the implantable device. For example, catheters are generally amenable to flushing with a solution of rifampin and minocycline or rifampin and novobiocin. For use in flushing solutions, the effective concentration of the antibiotic range from about 1 to 10 mg/ml for minocycline, preferably about 2 mg/ml; 1 to 10 mg/ml for rifampin, preferably about 2 mg/ml; and 1 to 10 mg/ml for novobiocin, preferably about 2 mg/ml. The flushing solution is normally composed of sterile water or sterile saline solutions.
Other methods of coating surfaces of medical devices with antimicrobial agents are taught in U.S. Pat. No. 4,895,566 (a medical device substrate carrying a negatively charged group having a pKa of less than 6 and a cationic antibiotic bound to the negatively charged group); U.S. Pat. No. 4,917686 (antibiotics are dissolved in a swelling agent which is absorbed into the matrix of the surface material of the medical device); U.S. Pat. No. 4,107,121 (constructing the medical device with ionogenic hydrogels, which thereafter absorb or ironically bind antibiotics); U.S. Pat. No. 5,013,306 (laminating an antibiotic to a polymeric surface layer of a medical device); U.S. Pat. No. 4,95,419 (applying a film of silicone oil to the surface of an implant and then contacting the silicone film bearing surface with antibiotic powders); and U.S. Pat. No. 4,442,133.
These and other methods of coating medical devices with antimicrobial agents appear in numerous patents and medical journal articles. However, these methods also have significant drawbacks in that they can alter the integrity of non-metallic medical devices or result in residual antimicrobial material precipitating within the device.
Accordingly, there is a need for a non-metallic medical device treated with an antimicrobial agent to provide a broad range of antimicrobial activity while minimizing the harmful side effects noted above. Further, there is a need for a method that results in low residual coating material left on the surface of the medical device, which reduces complications arising from precipitation of coating material within the device. There is also a need to enhance the versatility of the treatment to accommodate higher concentrations of antimicrobial agents if needed.
SUMMARY OF THE INVENTION
One aspect of the present invention is a method for treating non-metallic medical devices with an antimicrobial agent comprising the steps of mixing at least an antimicrobial agent, an acid solution, and glycerol to form an antimicrobial composition and applying the antimicrobial composition to at least a portion of the non-metallic medical device under conditions wherein an effective concentration of the antimicrobial composition binds to the non-metallic medical device.
In a specific embodiment, the antimicrobial composition may be formed by mixing antimicrobial agents and an acid solution and then adding glycerol.
In another specific embodiment, the antimicrobial agent may be selected from the chlorhexidine and methylisothiazolone; chlorhexidine and &agr;-terpineol; thymol and chloroxylenol; thymol and methylisothiazolone; chlorhexidine and cetylpyridinium chloride; chlorhexidine and chloroxylenol; chlorhexidine, methylisothiazolone and thymol; methylisothiazolone and &agr;-terpineol; minocycline and rifampin; and chlorhexidine, methylisothiazolone and &agr;-terpineol.
In another specific embodiment, the portion of the non-metallic medical device treated may be made from rubber, plastic, nylon, silicone, polyurethane, polyethylene, polyvinyl chloride, polytetrafluoroethylene tetraphthalate, polyethylene tetraphthalate, polytetrafluoroethylene, latex, elastomers, polymers, and materials sealed with gelatin, collagen or alumin.
In another specific embodiment, the non-metallic medical device may be a peripherally insertable central venous catheter, dialysis catheter, long term tunneled central venous catheter, peripheral venous catheter, short-term central venous catheter, arterial catheter, pulmonary artery Swan-Ganz catheter, urinary catheter, long term non-tunneled central venous catheters, peritoneal catheters, ventricular catheters, long term urinary devices, tissue bonding urinary devices, penile prostheses, vascular grafts, extravascular grafts, urinary stints, vascular catheter ports, wound drain tubes, hydrocephalus shunts, pacemaker systems, artificial urinary sphincters, vascular dialators, extravascular dialators, vascular stints, extravascular stints, small joint replacements, temporary joint replacements, urinary dilators, heart valves, orthopedic implants, heart assist devices, stents, penial implants mammary implants, and dental devices.
In another specific embodiment, the acid solution may be a short chain monocarboxylic acid and ortho-phosphoric acid. The short chain monocarboxylic acid may be formic acid, acetic acid, or propionic acid.
A further specific embodiment includes the ratio of monocarboxylic acid to ortho-phosphoric acid to glycerol may be about 79:8:13.
In another specific embodiment, the antimicrobial composition has a temperature that is between 2° C. to 75° C. at some point during the treatment, preferably about 45
Darouiche Rabih O.
Mansouri Mohammad David
Baylor College of Medicine
Beck Shrive P.
Fulbright & Jaworski LLP
Kolb Michener Jennifer
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