BACKGROUND OF THE INVENTION

1. Field of the Invention This invention relates to a method for the removal of residual microbicide from a percutaneous medical device, and more particularly to a method for the removal of residual hydrogen peroxide and peroxyacetic acid from a reprocessed percutaneous transluminal coronary angioplasty catheter.

2. Background of Related Art

Percutaneous transluminal coronary angioplasty (hereinafter PTCA) catheters are expensive and are presently used one time and then discarded. These catheters have a blind end or a closed end tube, such as a balloon.

An anti-corrosive microbicide (CATHx™) for use in sterilization procedures is disclosed in U.S. Application Serial Number 07/778,940, filed December 10, 1991, entitled "Anticorrosive Microbicide."

Hydrogen peroxide and peroxyacetic acid, essential ingredients in the anticorrosive microbicide described therein, are strong oxidizers and can cause myocardial damage or death if they are injected into the bloodstream.

CATHx™, or other microbicides, should not be used to reprocess PTCA catheters because it is difficult to remove residual hydrogen peroxide and peroxyacetic acid solution, or other microbicides, from the closed end. If the closed end ruptures during the time the PTCA catheter is reused, residual hydrogen peroxide and peroxyacetic acid solution could be injected into the bloodstream of a patient. To remove the residual hydrogen peroxide and peroxyacetic acid solution by repeated addition and removal of a suitable diluent such as water,

saline, and the like, takes 10-20 minutes or longer. Conventional methods for removing residual microbicides, such as hydrogen peroxide and peroxyacetic acid, from percutaneous medical devices, such as catheters, are inefficient, costly and time consuming.

SUMMARY OF THE INVENTION An object of the present invention is to provide a simple, fast and effective method for removing residual microbicides from a percutaneous medical device.

A further object of the present invention is to provide a method for removing residual hydrogen peroxide and peroxyacetic acid from a reprocessed PTCA catheter.

An embodiment of the invention relates to a method for removing residual microbicide from a percutaneous medical device comprising contacting the surfaces of the medical device with sufficient amount of a neutralizing solution to neutralize the residual microbicide, wherein the neutralizing solution and reaction products of the neutralizing solution and the microbicide are injectable into a human bloodstream. Another embodiment of the invention relates to a method for reprocessing a used PTCA catheter comprising removing residual hydrogen peroxide and peroxyacetic acid from the catheter by passing a sufficient amount of a neutralizing solution through the catheter to neutralize residual hydrogen peroxide and residual peroxyacetic acid, wherein the neutralizing solution and reaction products of the neutralizing solution, the hydrogen peroxide and the peroxyacetic acid are injectable into a human bloodstream.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An embodiment of the invention relates to a method for removing residual microbicide from a percutaneous medical device comprising contacting the surfaces of the medical device with sufficient amount of a neutralizing solution to neutralize the microbicide, wherein the neutralizing solution and reaction products of the neutralizing solution and the microbicide are injectable into a human bloodstream and non-toxic to humans.

The percutaneous medical device can be, for example, a used percutaneous medical device which has been sterilized by the microbicide and residual microbicide remains on the surfaces thereof. After removing the residual microbicide according to the present invention, the used percutaneous medical device is reprocessed and can be reused in a patient.

Another embodiment of the invention relates to a method for reprocessing a used PTCA catheter comprising removing residual hydrogen peroxide and peroxyacetic acid from the catheter by passing a sufficient amount of a neutralizing solution through the catheter to neutralize residual hydrogen peroxide and residual peroxyacetic acid, wherein the neutralizing solution and reaction products of the neutralizing solution, the hydrogen peroxide and the peroxyacetic acid are injectable into a human bloodstream. The microbicide can be any conventional microbicide provided that the reaction products of the microbicide and the neutralizing solution are injectable into the human blood stream. The microbicide preferably includes hydrogen peroxide and peroxyacetic acid, for example, CATHx™, the formula of which is disclosed below in Example 1. The microbicide can include conventional

additives, for example, an anti-corrosive agent.

Preferably the neutralizing solution reduces hydrogen peroxide to water and reduces peroxyacetic acid to acetic acid and water. The neutralizing solution contains, for example, an enzyme, a metal ion or ascorbic acid, which converts residual hydrogen peroxide to water and converts residual peroxyacetic acid to water and acetic acid. Preferably, the neutralizing solution contains ascorbic acid.

If ascorbic acid is used, the neutralizing solution can be, for example, a sterile solution in water of 250 mg/ l of ascorbic acid along with a sufficient amount of an agent, such as sodium hydroxide, sodium carbonate or sodium bicarbonate, to adjust the pH between about 5.5 to about 7.0.

Ascorbic acid (vitamin C) is an effective reducing agent going from ascorbic acid to dehydroascorbic acid, as follows:

HO-CH HO-CH

/ / H ₂ C-OH H ₂ C-OH

If residual hydrogen peroxide is present on the percutaneous medical device, the ascorbic acid will convert the residual hydrogen peroxide to water by the following reaction: H ₂ 0 ₂ + 2H ⁺ > 2H ₂ 0

If residual peroxyacetic acid is present on the percutaneous medical device, the applicants believe to the best of their ability that the ascorbic acid will convert the residual peroxyacetic acid to water and acetic acid by the following

reaction:

CH _j COOOH + 4H ⁺ —> CH _j COOH + H ₂ 0 ₂ + 2H ⁺ —> CH ₃ COOH + 2H ₂ 0

If the above reaction products of ascorbic acid, hydrogen peroxide, and peroxyacetic acid are injected into the bloodstream of a human, the body can change the oxidized form of ascorbic acid back to ascorbic acid. Administration of large doses of ascorbic acid into the bloodstream of a human produces few demonstrable effects. The LD 50

(lethal dose) for ascorbic acid in mice is 518 mg/kg and rats is 4 g-m/kg. The TDO (tolerated dose, no effect) in women is 900 mg/kg.

Excessive concentrations of ascorbic acid are difficult to achieve in the body. The renal threshold for ascorbic acid is about 1.5 mg/dl of plasma (85 mM) and increased amounts of ascorbic acid are excreted. "Megadose" practices, such as for preventing or curing the common cold, have shown a "rebound" scurvy phenomenon where subjects who are consuming large amounts of ascorbic acid suddenly stop consuming ascorbic acid. This is presumably due to induction of pathways of ascorbic acid metabolism as a result of the extended high dosage. The acetic acid formed by the reaction of residual peroxyacetic acid and ascorbic acid is at such a low concentration that no demonstratable effects are produced. The LD50 of acetic acid in mice is 525 mg/kg, which is greater than the level of ascorbic acid.

The present invention can be used to reprocess a used percutaneous medical device, for example, a PTCA catheter. Immediately after use in a patient, the percutaneous medical device to be reprocessed is preferably submerged in a sterile saline solution to prevent blood and contaminants on the surface thereof from drying. Preferably, excess

blood and contaminants are wiped off the surface. If the percutaneous medical device is a PTCA catheter, it is preferably flushed with saline before sterilizing. The percutaneous medical device is then reprocessed with a microbicide to sterilize it. If the percutaneous medical device contains an inner space, such as the balloon on a PTCA catheter, a syringe can be used to force the microbicide into the percutaneous medical device.

The sterilized percutaneous medical device can be stored for up to about 14 days.

Before the sterilized percutaneous medical device can be reused, the microbicide must be neutralized. Before neutralizing the microbicide in the percutaneous medical device, excess sterilizing solution is preferably removed from the inside of the percutaneous medical device.

The surfaces of the sterilized percutaneous medical device are then rinsed with the neutralizing solution to neutralize the microbicide.

If a microbicide containing hydrogen peroxide, such as CATHx™, was used to sterilize the percutaneous medical device, after rinsing the percutaneous medical device with the neutralizing solution, the concentration of residual hydrogen peroxide is tested. If the concentration of hydrogen peroxide is not at a safe or non-toxic level to be injected into a human bloodstream, the percutaneous medical device is rinsed again with a fresh neutralizing solution and the concentration of hydrogen peroxide retested. This procedure is repeated until the concentration of hydrogen peroxide is safe or non-toxic for injecting into the human bloodstream, for example, less than about 440 ppm. More preferably the level of hydrogen peroxide is less than or equal to about 10 ppm.

When ascorbic acid is used in the neutralizing solution, the preferred amount is greater than the molar equivalent of the amount of hydrogen peroxide present in the percutaneous medical device. This amount can be approximated, for example, by assuming the worst case situation. The worst case for a typical PTCA catheter is when the PTCA catheter has not had any CATHx™ removed before the neutralizing solution is introduced and the catheter holds the maximum volume of fluid possible, which is slightly less than lcc.

More preferably, the amount of ascorbic acid used is about 1000 mg or more to neutralize the residue in a typical PTCA catheter. A syringe can be used to force the ascorbic acid solution into the percutaneous medical device, such as a PTCA catheter. For example, a 5 cc syringe containing the equivalent of about 2 cc of 500 mg/ml, sterile, liquid ascorbic acid can be used to flush the inside of a typical PTCA catheter having a balloon as follows.

The syringe filled with the ascorbic acid solution can be attached to the balloon port of the catheter. The balloon can be, for example, inflated and deflated with the ascorbic acid solution for a total of about one minute. The balloon can be inflated by depressing the plunger and holding for about three seconds. The balloon can be deflated by withdrawing the plunger the length of the syringe and holding for three seconds. Bubbles will appear in the catheter tubing, balloon and in the syringe.

The syringe can then be, for example, removed from the balloon port and attached to an infusion lumen port so that the ascorbic acid solution can be flushed through the lumen.

To test the final residual hydrogen peroxide concentration in a catheter balloon, for

example, a sterile syringe can be attached to the balloon port and a small amount of liquid withdrawn therefrom. The syringe can then be removed from the catheter and the sample of liquid within the syringe can be tested using, for example, CATHx™ Residual Test Strips (Minntech Corp., Minneapolis, MN) , to insure the liquid in the catheter contains about 10 ppm hydrogen peroxide or less.

The CATHx™ Residual Test Strips detect inorganic or organic compounds which contain a peroxide or a hydroperoxide group. The test strip is dipped into the solution to be tested for about one second, to properly wet the reaction zone. Peroxidase contained in the reaction zone transfers oxygen from the peroxide to an organic redox indicator in the reaction zone which is converted to a blue-colored oxidation product. The color of the reaction zone is compared to a color scale after about 15 seconds to determine the concentration of peroxide. If any blue coloration appears within about 3 minutes, a positive reaction for peroxide has occurred.

To test the final residual hydrogen peroxide concentration in a catheter lumen, for example, a sterile syringe can be attached to the infusion lumen port and a sample of the liquid can be pushed out the tip of the catheter. The sample can be tested using, for example, CATHx™ Residual Test Strips to insure the liquid in the lumen contains about 10 ppm hydrogen peroxide or less.

Even though the PTCA catheter can be reused if the hydrogen peroxide concentration is below about 440 ppm, the preferred concentration before reuse is about 10 ppm. If any part of the PTCA catheter tests above about 10 ppm it is preferably flushed again with neutralizing solution. The reprocessed PTCA catheter can be

reused immediately after flushing with the neutralizing solution. Preferably, excess neutralizing solution is removed from the inside of the PTCA catheter before reusing. When reprocessing a monorail catheter, the neutralizing solution can be diluted with sterile saline to compensate for the increased volume of the monorail catheter so that the balloon is fully inflated during neutralization. The lumen of the monorail can be flushed using the catheter monorail adapter.

The method according to present invention can be automated. For example, in commonly owned U.S. Patent No. 4,721,123, the disclosure of which is incorporated herein by this reference, an automated reprocessing system is disclosed which can be used to perform the method according to the present invention. Commonly owned Application No. 07/835,729, which is incorporated herein by this reference, discloses another reprocessing and sterilizing system that can be used to perform the method according to the present invention, which uses a unique catheter sterilizing cassette that permits storage of sterilized catheters for periods of one week to one month without breaks in sterility. Commonly owned Application No. 08/097,891, which is incorporated herein by this reference, discloses an adaptor so that monorail- type or rapid exchange catheters can be reprocessed, in particular in a reprocessing system of the type disclosed in the '729 application.

EXAMPLE I

Test solutions of CATHx™ were neutralized with ascorbic acid and evaluated for their potential to cause hemolysis to the blood of the rabbit. A pilot study and a main study were conducted. The

susceptibility of the rabbit to a known hemolytic agent, purified water, was substantiated at NAmSA with this method.

The study was conducted in accordance with the provisions of the Good Laboratory Practice (GLP) Regulations, 21 C.F.R. 58, et. seq. A Certificate of Quality Assurance Inspections was issued in conjunction with this report.

CATHx™ was made by mixing together part A and part B as follows:

Part A: 18% - 30% by weight hydrogen peroxide 6% - 10% by weight acetic acid 3% - 5% by weight peroxyacetic acid balance water Part B: .1% Victawet® balance water

The combined concentration was as follows:

Hydrogen peroxide 0.004% - 30% by weight Acetic acid 0.025% - 12% by weight Peroxyacetic acid 0.0003% - less than 55% by weight Victawet® 0.001% - 0.1% by weight

Water balance

Victawet® comprises the following: a) 20%-45% by weight mono sodium salt of phosphoric acid, mono (2-ethyl hexyl) ester; b) 20%-30% by weight pyrophosphonic acid, bis (2-ethyl hexyl) esters, sodium salts; c) 10%-25% by weight polyphosphonic acids, 2-ethyl hexyl esters, sodium salts; d) 20%-25% by weight water; e) less than 10% by weight phosphoric acid, bis (2-ethyl hexyl) ester, sodium salt; f) less than 3% by weight 2-ethyl hexanol; and

g) less than 5% by weight phosphoric acid, sodium salts, mono and di.

The temperature was room temperature. In the pilot and main studies, CATHx™ was mixed with two parts of ascorbic acid (AA) by volume. In the pilot study 10 ml of CATHx™ was mixed with 20 ml of AA and in the main study 20 ml of CATHx™ was mixed with 40 ml AA. The concentration of the AA was 500 mg AA per ml of water. Each solution was tested 1 minute after mixing.

Four healthy rabbits of the New Zealand White variety were obtained from a USDA licensed supplier traceable in NAmSA records. These animals were acclimated to the laboratory as specified in the NAmSA Testing Services (Northwood, OH) using standard operating procedures ("SOP") . Animal weights were between 2.0 kg and 3.0 kg; no particular rabbit gender or age range was prescribed for this test by NAmSA SOP.

Rabbits, identified by ear tag or tattoo, were individually housed in suspended cages and received a commercially pelleted rabbit feed on a daily basis; tap water was freely available. No diet or water analysis was performed since there were no contaminants suspected that could interfere with this study. Animal husbandry and environmental conditions conformed to current NAmSA SOP's which are based on the "Guide for the Care and Use of Laboratory Animals," NIH Publication No. 85-23.

The pilot study was conducted prior to the main study to determine if the dose as set in the protocol would have any toxic effect when injected. The pilot study followed the methods and procedures of the protocol; however, no blood samples were taken nor were the rabbits tranquilized. Stock

- ll -

rabbits scheduled for euthanasia were used.

In the main study, prior to injection, the rabbits were tranquilized with an intramuscular injection of acepromazine maleate. A sample of blood from the middle ear artery of each rabbit was collected (EDTA vacutainer) to serve as a pretreat reference value.

Based on results of the pilot study, the dose of the main study was set at 3 ml/rabbit. The test solution was then slowly injected intravenously via the marginal ear vein into each of two rabbits at the prescribed dose.

No sooner than 1 minute, but within 5 minutes of treatment, a sample of blood was collected from each rabbit. Blood samples were then centrifuged at 2200 rp to obtain plasma samples.

Determinations of free iron levels (ppm) in plasma were obtained by atomic absorption spectrophotometry. Posttreatment results comparable to the pretreatment results (less than or equal to a

1.00 ppm increase) were judged to be normal. A difference greater than 1.00 ppm between pretreatment and posttreatment values was considered as evidence of hemolysis. The pre and post difference demonstrated in 95% of the animals dosed with water ranged from 1.01 to 5.53 ppm.

All animals used in the study were euthanatized by injection of a sodium pentobarbital based drug following clinical observations conducted up to 4 hours after injection.

In the pilot study, the first rabbit injected at 5 ml/kg reacted adversely upon injection (gasping, cyanotic) and was euthanatized immediately for humane reasons. The second rabbit, injected at 2.5 ml/kg, exhibited slight swelling at the injection site but otherwise appeared normal after injection.

In the main study, both animals dosed at 3.0 ml/rabbit appeared normal immediately af er injection and at 2-4 hours after treatment. Plasma iron values are shown in Table I.

TABLE I

Body PLASMA IRON LEVELS (PPM)

Rabbit Weight Number (kg) Pretreat Posttreat Difference Mean Difference

70422 2.0 2.49 2.24 (-) 0.25

(-) 0.17

70439 2.1 2.42 2.34 (-) 0.08

Under the conditions of the main study, the test solution was not considered hemolytic. There was no increase in plasma iron between the pre and posttreatment determinations.

EXAMPLE II The toxicity of CATHx™ was tested by two independent laboratories NAmSA Testing Services

(Northwood, OH) and Viromed Laboratories, Inc.

(Minneapolis, MN) . The results of these tests are summarized in Table II. TABLE II toxic level non-toxic level NAmSA Viromed NAmSA Viromed PPM dil PPM dil PPM dil PPM dil

Peroxyacetic 6.3 1:200 5.3 1:280 4.3 1:300 4.9 1:300 acid hydrogen 36. 1:200 29 1:280 24. 1:300 27. 1:300 peroxide

The NAmSA test data was based on agarose overlay of L-929 mouse fibroblast cells. Levels tested included a 1:300 and a 1:200 dilution of the mixed, ready to use Cathx. The 1:200 level was toxic, the 1:300 was not.

Viromed test data was based on agarose overlay of L-929 mouse fibroblast cells. Levels

tested were 1:200, 1:220, 1:240, 1:260, 1:280, 1:300 and 1:400 dilution of the mixed, ready to use CATHx™. The 1:280 level was toxic, the 1:300 was not. The applicants believe to the best of their ability that NAmSA followed the same test procedures as VIROMED which were as follows. The above cytotoxicity assay was designed to screen the biological reactivity of mammalian cell cultures following contact by diffusion of leachable, cytotoxic chemicals in materials or formulations. The L-929 cell line has a significant history of use in assays of this type.

Cultures of L-929 cells (mouse fibroblast, ATCC CCL-1) were originally obtained from the

American Type Culture Collection, Rockville, MD. The medium used for growth of cells and preparation of extracts is Eagle's minimal essential medium (E- MEM) supplemented with 10% (v/v) heat inactivated fetal bovine serum (fbs) . The medium may also be supplemented with glutamine (2mM) and one or more of the following antibiotics: gentamicin (50 ug/ l) , penicillin (100 units/ml), amphotericin B (2.5 ug/ml) . Cultures were maintained and used as monolayers in 60mm diameter tissue culture plates at 37°C in a humidified atmosphere of 5% CO in air.

Agar overlay medium contained E-MEM with 2mM glutamine, not more than 2% agarose, 2-5% fbs, and one or more of the antibiotics described above. Alternative Cell Lines include:

WI-38 (ATCC CCL-75) human embryonic lung propagated and maintained on E-MEM with 10% fbs and antibiotics, and MRC-5 (ATCC CCL-171) human embryonic lung propagated and maintained on E-MEM with 10% fbs and antibiotics.

The size of the article to be tested was determined by the following ASTM guidelines:

1. Liquids or extracts will be prepared by saturating each sterile noncytopathic filter disk (Millipore AP2501000) with 0.1 ml aliquot.

2. Where a test article is sufficiently small to fit into the culture dish leaving an adequate margin of cells for evaluation, the entire article will be used.

3. Large solid materials and devices will be cut in cross-section to obtain a flat surface having an area of 100 to 250mm ² to be placed in direct contact with the agarose surface.

4. Articles of rod or tubing or of rod- or tube-shaped devices will be prepared as follows: a. Where the diameter is less than

6.4mm, sections 5 to 15 mm in length will be cut.

b. Where the diameter is 6.4 to 15mm, sections 2 to 8mm in length will be cut.

c. Where the diameter exceeds 15mm, cross-sections will be prepared as described in 3.

Monolayers of L-929 cells were prepared in

60mm diameter plates and grown until confluent.

Duplicates of the test article(s) and controls were placed on the agarose surface of the test plates. A cell control plate was run concurrently. The plates were incubated at 37°C in 5% C0„ for 24 ± l hours.

2

Plates were stained with a neutral red

solution and scored macroscopically and microscopically. Results were scored as toxic or nontoxic based upon observations of cells lysis and definitive cytotoxic effects at the sample sites. Sites were given numerical values to indicate the following lysis/cell death index. Zone index is a measure of area affected by the test article based upon visual observation of neutral red uptake.

Zone Index Description

0 No detectable zone under or around specimen.

1 Some malformed or degenerated cells under sample.

2 Zone limited to area under specimen. 3 Zone extends 0.5 - 1.0 cm beyond specimen. 4 Zone extends greater than 1.0 cm beyond specimen. The above Viromed test procedure is published in U.S. Pharmacopeia U.S.P. XXII, 5th Supplement, page 2702 (U.S.P. 1991) which is incorporated herein by this reference.

Viromed also ran the above cytotoxicity test on Cidex7 (Sugikos, Arlington, Tx) based on agarose overlay of L-929 mouse fibroblast cells. Cidex7 is a reusable sterilizing and disinfecting solution containing 2.0% glutaraldehyde as the active ingredient. The final use dilution was tested. The results were as follows: dilution tested result

1:1,000 (of the use toxic 1:5,000 dilution) toxic 1:10,000 non-toxic

1:15,000 toxic 1:20,000 non-toxic

This test indicates that CATHx™ has a lower cytotoxic potential than Cidex 7. The test procedures were the same as the Viromed test procedures above.

The detoxification of CATHx™ by ascorbic acid was also tested by Viromed based on agarose overlay of L-929 mouse fibroblast cells following the same procedure as above. The results are summarized in Tables III and IV as follows.

TABLE III

CATHx; with neutralizer

CATHx as is (already diluted 1:3) non¬ non- non¬ toxic toxic toxic toxic toxic toxic

PPM dil PPM dil PPM PPM PPM PPM Peroxyacetic 5.3 1:280 4.9 1:300 407. 40.7 110 73 acid hydrogen 29. 1:280 27. 1:300 2530. 250. 660 440 peroxide (no (1:10 Dilution) of the

"diluted" CATHx™)

Ascorbic acid With neutralized CATHx as is (500 mg/ml) (already diluted 2:3) toxic non-toxic toxic non-toxic PPM PPM PPM PPM

Ascorbic 11,000 5,500 333,000 33,000 acid (1:30 (1:60 (no (1:10 dilution) dilution) dilution dilution) of the

"diluted" product)

TABLE IV

Cytotoxicity of CATHx™

Based on cytotoxicity testing, mix tested (in mis) Dilutions tested

Cathx ascorbic H ₂ 0 as is 1:4 1:6 l:: 10

1.0 0.1 1.9 OK OK OK OK

1.0 0.25 1.75 tox OK OK OK

1.0 0.5 1.5 tox OK OK OK

1.0 1.0 1.0 tox tox OK OK

1.0 1.5 0.5 tox OK OK OK

1.0 2.0 0.0 tox tox tox OK

This data indicates that an approximate ratio of one mole of hydrogen peroxide to one mole of ascorbic acid provides the best neutralization effect based on cytotoxicity testing. This level minimizes the cytotoxicity seen with either the hydrogen peroxide or the ascorbic acid alone.

Based on the above, the detoxification of CATHx™ is about one log reduction. The applicants believe that the detoxification may be even greater.

EXAMPLE IV

A production lot of CATHx™ was taken to BETEC Laboratory (Minneapolis, MN) to be tested for hydrogen peroxide. After mixing part A and part B in the same manner as in Example 1, one ml of the freshly mixed CATHx™ was tested for hydrogen peroxide using the UPS XXII, spot test with K ₂ Cr ₂ 0 ₇ , which is published in U.S. Pharmacopeia U.S.P. XXII, 5th Supplement, (U.S.P. 1991) , which is incorporated herein by this reference. The CATHx™ gave a strong positive test for hydrogen peroxide. A one ml sample of this freshly made solution was mixed with one ml of an ascorbic acid solution containing 500 mg/ml ascorbic acid. This solution was mixed by gently swirling in a test tube. Approximately 30 seconds after adding the ascorbic acid solution, the sample was tested for peroxide and a very trace positive result was seen. Another one ml sample of CATHx™ was taken and two mis of the ascorbic acid solution was added thereto and mixed the same way as the first addition. The sample was tested as above and showed negative for peroxide.

The ascorbic acid used was ascorbic acid injection USP 500mg/ml McGuff Company lot 2601 MG expiration date 10/94, containing no preservative.

EXAMPLE V

An intra-arterial injection study of the materials identified below was conducted in 12 rabbits. The purpose of the study was to evaluate systemic toxicity, local irritation, and general cardiac effects following injection of various materials into the central ear artery of rabbits.

Group Material Preparation

1 CATHx, One bottle of Part A was

Lot 71D325X-0043, added to one bottle of exp 01-94 Part B. The resulting mixture was agitated thoroughly.

0.9% sodium chloride USP Dosed "neat" solution, lot J3C301 (saline) *

Air The plunger of a sterile

(bolus injection) syringe was pulled back to the 5.0 ml mark. 4 Same as Group 1 Same as Group 1 5 Ascorbic Acid Dosed "neat" (250 mg/ml) , lot #92L890

CATHx/Ascorbic acid 1.0 ml of the prepared mixture CATHx was mixed with 4.0 ml of the Ascorbic acid (250 mg/ml)

Saline*/radiographic 1.5 ml of each were mixed contrast media together (Omnipaque® 350)* 8 CATHx/Ascorbic 1.0 ml of the prepared acid/saline/radiographic CATHx, 4.0 ml of ascorbic contrast media acid, 1.5 ml of saline, and 1.5 ml of contrast media were mixed together

Twelve healthy female rabbits of the New

Zealand White variety were obtained from a USDA licensed supplier. These animals were acclimated to the laboratory as specified in NAmSA SOP. Animal

weights were between 3.4 kg to 4.6 kg and no particular rabbit gender or age range was prescribed for this test.

Rabbits, identified by ear tag or tattoo, were individually housed in suspended cages and received a commercially pelleted rabbit feed on a daily basis; tap water was freely available. No diet or water analysis was performed since there were no contaminants suspected that could interfere with this study. Animal husbandry and environmental conditions conformed to current NAmSA SOP which are based on the "Guide for the Care and Use of Laboratory Animals," NIH Publication No. 85-23.

Each rabbit was weighed and anesthetized by intramuscular injection of a combination of ketamine hydrochloride/xylazine (34 mg/kg + 5 mg/kg) at a dose of 0.6 ml/kg. The animals were then placed on halothane/oxygen inhalation for continued general anesthesia during the procedure. A blood sample was collected from each animal prior to dosing. Animals were then connected to the electrocardiograph and a pretreat tracing (ECG) of cardiac activity was obtained.

Each animal was injected intra-arterially via the middle ear artery with the designated material using a 20 gauge needle as follows:

Group Material No. of Animals Dose (per animal)

1 CATHx (Sterilant: 2 1.0 ml Parts A and B mixed)

2 0.9% sodium 2 1.0 ml chloride USP solution

3 Air bolus 2 5.0 ml

4 CATHx (same as 2 2.0 ml Group 1)

Ascorbic acid: 4.0 ml 250 mg/ml concentration

Mix of 1.0 ml 5.0 ml CATHx with 4.0 ml Ascorbic acid (250 mg/ml)

A 50/50 mix of 3.0 ml saline/ radiographic contrast media

Mix of 1.0 ml 8.0 ml CATHx, 4.0 ml Ascorbic acid, 1.5 ml saline, 1.5 ml radio¬ graphic contrast media

The animals were observed for any clinical signs immediately, at 10 minutes, 4 and 24 hours after injection. The veterinarian was consulted immediately in the event of any adverse health finding.

An ECG tracing of cardiac performance was obtained before, during and after dosing. Intervals for postdose tracings were varied and at the discretion of the staff veterinarian. A blood sample was collected from each

animal prior to dosing and from surviving animals at approximately 24 hours after dosing. Animals were anesthetized prior to the blood draw. The pretreatment blood draw was obtained from the central ear artery while the postdose draw was from the abdominal aorta or posterior vena cava. Blood samples were allowed to clot and then centrifuged to obtain serum. Half the serum for each sample was frozen and half was kept at room temperature. At approximately 24 hours after dosing, surviving animals were anesthetized and exsanguinated following blood draw. Macroscopic observations of the viscera, including the heart, were conducted on these or any animal found dead before this interval. The heart and ears of all euthanatized animals were excised and placed in 10% neutral buffered formalin. The heart was retained from animals that died.

Analyses of the ECG tracings were conducted by Cardiopet, Inc. The electrocardiograph readings attained before, during and after dosing were evaluated.

Serum sample analyses were conducted by Roche Bioveterinary Services (Division of Roche Biomedical Laboratories, Inc.). The evaluation entailed enzyme testing for creatine kinase ("CPK") , lactic acid dehydrogenase ("LDH") and isoenzymes of each.

The ears from animals in Groups 2, 4, and 6 were chosen by the sponsor for histopathology. A cross section of the ears through the blood vessels were routinely embedded in paraffin, cut, and stained in hematoxylin and eosin. Microscopic evaluation was then conducted by R.F. McConnell, D.V.M. , a board certified veterinary pathologist.

Group 1 animals upon injection of 1.0 ml of CATHx (Parts A and B mixed) exhibited discomfort

and abnormal respiration. At the 10 minute observation, and for the remainder of the study, the injected ears were discolored, edematous and were drooping to the side of the head. By the 4 hour interval, breathing was normal. At 24 hours, facial edema, ventral cervical edema and slight lethargy were noted.

Group 2 animals dosed with 0.9% sodium chloride solution appeared normal. One of the group 3 animals had abnormal respiration upon injection of air and after 10 minutes. The animal was recumbent at 4 hours and then found dead the following day. The other animal exhibited abnormal respiration following dosing and was dead approximately 20 minutes following dosing.

The group 4 animals dosed with 2.0 ml CATHx appeared much the same as Group 1 animals except lethargy was more severe, salivation was observed, and chemosis was noted for the nictitating membrane of the eye located on the same side as the injected ear.

The group 5 animal exhibited abnormal respiration and discomfort upon injection of the ascorbic acid; otherwise the rabbit appeared normal. The group 6 animal exhibited abnormal respiration upon injection of the CATHx/ascorbic acid mixture; otherwise the animal appeared normal.

The group 7 animal, dosed with saline/radiographic contrast media, appeared normal. The group 8 animal exhibited abnormal respiration and discomfort upon injection of the mixture of CATHx, ascorbic acid, saline and contrast media; otherwise the rabbit appeared normal.

For Groups 1, 3, and 4, areas of the myocardium appeared pale in color especially over the ventricles; otherwise, there were no macroscopic changes in the viscera at necropsy for any animal.

In the evaluation of ECG tracing, only one animal, from Group 3, exhibited any major abnormality. Other atrial premature complexes observed for other animals were considered of normal variation.

The average values of CPK and LDH, before injection and 24 hours after injection, for each group of animals are shown in Table V.

TABLE V SUMMARY OF RABBIT ENZYME DATA-CATHX TESTING

CPK LDH # of animals start 24 hr start 24 hr

1 ml CATHX/rbt. 1764 24,980 465 841 2

1 ml saline/rbt. 1363 13,502 180 402 2

5 ml air/rbt. 2125 "2,156" 270 "153" 1 (30 minutes for "24 hour" value)

2 ml CATHX/rbt. 1096 52,118 141 935 2

4 ml ascorbic 1552 16,544 352 628 1 acid/rbt.

1 ml CATHX + 4 ml 891 11,808 100 379 1 ascorbic acid/rbt.

1.5 ml contrast 1365 28,032 153 692 1 media + 1.5 ml saline/rbt.

1 ml CATHX + 1579 29,136 214 793 1 4 ml ascorbic acid + 1.5 contrast media + 1.5 ml saline/rbt

Posttreatment CPK values were elevated in Groups 1, 2, and 4-8, but only Groups 4-6 appeared to show marked increases over that of the saline Group 2.

In human testing, an increase in creatine phosphokinase ("CPK") or in lactic dehydrogenase ■ ("LDH") , or both, indicate myocardial infarction. CPK increase has a sensitivity of 93-100% with a 57- 88% specificity and LDH increase has a sensitivity of 87% with a specificity of 88%. The applicants believe that these indications are probably about the same in rabbits.

EXAMPLE VI

The gas evolution from CATH™ being neutralized by the materials shown in Table VI was tested using a modified Warburg manometer.

TABLE Vi Gas generation of CATHx with different additivesAteutralizers". materials already mixed Total volume of gas generated at a given time (in mis) before mixing to measure system stability; and after mixing (in cc) mixture cathx other 40 sec 2 mm 5 mm to be added blood Before -0.007 -0.007 -0.010 1.0ml mixing

After 0.067 0.077 0.094 mixing blood Before 0.067 0.137 0.181 1.0ml mixing

After >1.02 mixing blood Before 0.023 0.017 0.013 1.0ml mixing

1.0 2.0

After 0.077 0.101 0.127 mixing blood Before 0.027 0.030 0.023 1.0ml mixing

After 0.067 0.097 0.114 mixing blood Before 0.033 0.057 0.101 1.0ml mixing

2.0 myochrysine (gold sodium thiomatate. After inj.) mixing >1.0 blood Before 0.027 0.033 0.027 1.0ml mixing

2.0 cisplatin inj. (platinol-aq) After >1.0 mixing

15mg Before 0.0 0.0 -0.02 cata- mixing sal. Blood 1.0ml After 0.077 0.087 0.111 mixing blood Before 0.0 0.047 0.064 1.0ml mixing

After 0.58 0.823 >1.0 mixing blood Before -0.007 -0.020 -0.020 1.0ml mixing

0.5

After 0.208 0.235 0.329 mixing blood Before 0.033 0.044 0.044 1.0ml mixing

After 0.064 0.070 0.070 mixing

Gas generation of CATHx with different additives neutralizers". materials already mixed Total volume of gas generated at a given time (in mis) before mixing to measure system stability; and after mixing (in cc) mixture cathx vitC saline 40 sec 2 mm 5 mm to be added blood Before 0.013 0.027 0.060 1.0ml mixing S5%02

After 0.124 0.124 0.137 mixing blood Before 0.0 0.0 1.0ml mixing S5%02 2.0

After 0.077 0.087 0.111 mixing blood Before 0.030 0.064 0.087 1.0ml mixing S5%02

After 0.094 0.114 0.131 mixing blood Before 0.0 0.040 0.070 1.0ml mixing 5S%02

After 0.060 0.060 0.107 mixing

The data in Table VI illustrates that ascorbic acid dramatically reduces gas evolution from CATHx after contact with blood. Gold (Myochrysine) and platinum (cisplatin) do not. Both gold and platinum compounds had significantly more gas evolution after mixing with blood and CATHx™ than blood, CATHx™, and ascorbic acid and about the same volume of gas evolution as blood, CATHx™, and saline. The data in Table VI also illustrates that there is a relationship to gas generation and the ratio of ascorbic acid to CATHx™ . In the test situation, a plateau of decreasing gas evolution seems to be reached at a 1.0 ml CATHx™ to a 1.0 ml (500mg/ml) ascorbic acid with no further obvious decrease in gas evolution above this point.

The data in Table VI further illustrates that the addition of catalase to a blood/CATHx/ascorbic acid mix does not cause an increase in gas evolution above that seen by adding blood to a CATHx/ascorbic acid mix.

Based on the data in Table VI, the degree of blood oxygenation seems to play a minor part in gas evolution with the larger oxygen saturation of the blood (55%) showing a larger increase in gas evolution than that seen with a lower oxygen level (26%) .

The data in Table VI supports the idea of toxicity effects in the total animal being caused by gas embolism is also supported by information in the literature suggesting gas emboli due to hydrogen peroxide getting into the blood circulation.

The data in Table VI is presented as gas generated just before mixing and just before mixing to give an indication of the reactivity of the system prior to mixing (a "system blank") .

While the invention has been described in

detail, it is apparent to one of ordinary skill in the art that various modifications can be made without departing from the scope or spirit thereof.