Patent Publication Number: US-2007105758-A1

Title: Vancomycin formulations having reduced amount of histamine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims priority based upon U.S. Provisional Application Ser. No. 60/731,664 filed Oct. 31, 2005, U.S. Provisional Application Ser. No. 60/731,693 filed Oct. 31, 2005 and U.S. Provisional Application Ser. No. 60/731,776 filed Oct. 31, 2005, which are expressly incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION  
      The invention is related to pharmaceutical compositions for treating bacterial infections. In particular, the invention is related to a vancomycin pharmaceutical composition that has a reduced amount of histamine, and to vancomycin formulations that control the rate of release of histamine in the body.  
     DESCRIPTION OF RELATED ART  
      Vancomycin is a tricyclic glycopeptide antibiotic derived from  Amycolatopsis orientalis  (formerly  Nocardia orientalis  and  Streptomyces orientalis ). The glycopeptide has the chemical formula C 66 H 75 Cl 2 N 9 O 24 .HCl. Vancomycin is used to treat infections by Gram positive bacteria. It is a primary treatment of infections by Methicillin Resistant  Staphylococcus aureus  (MRSA) or for Methicillin Sensitive  S. aureus  (MSSA) infections in β-lactam allergic patients. Vancomycin is an antibiotic of last resort. It is typically reserved for these severe infections in order to prevent increased resistance to vancomycin in the population. Vancomycin is increasingly important owing to the emergence of bacteria with resistance to multiple anti-infectives.  
      Vancomycin dosing is typically three times daily. Dosing is usually by slow infusion in order to avoid two major side effects: phlebitis at the injection site and “Red Man Syndrome” (RMS). Phlebitis is typically resolved by suspending therapy, and changing injection sites and/or changing from peripheral to PICC catheters. RMS is typically resolved by suspending therapy, administering an anti-histamine, and resuming therapy at slower infusion rates. RMS, also known as the “red-man”, “red man&#39;s”, “red neck” or “red person&#39;s” syndrome, is a commonly recognized adverse reaction of vancomycin administration. It is characterized by a complex of symptoms including: pruritis, urticaria, erythema, angioedema, tachycardia, hypotension, occasional muscle aches, and a maculopapular rash that usually appears on the face, neck and upper torso. Cardiovascular toxicity may occur resulting in cardiac depression and cardiac arrest. Patients commonly begin to experience itching and warmth over their head and chest, with or without the development of a rash. The onset of RMS usually occurs within 30 minutes of the start of the infusion, but it may also occur after the infusion has ended. The reaction typically resolves between one and several hours after the end of the infusion. Hypotension, or low blood pressure, may also occur in the absence of other symptoms associated with RMS.  
      The precise cause of RMS is unknown. Despite the replacement of the old formulation of vancomycin, commonly described as “Mississippi Mud” due to its coloring attributable to impurities, the newer and purer vancomycin products still produce side effects, including RMS. The rate of infusion recommended by the manufacturer of vancomycin is no greater than 10 mg/min, over at least one hour. Two hour infusions are typical owing to the potential for RMS to occur. The RMS reaction is usually associated with a rapid rate of infusion, but two cases of possible RMS have been reported after oral administration of vancomycin. Even at slower rates of infusion, vancomycin has caused hypotensive reactions.  
      Several studies have suggested that vancomycin directly causes histamine release as measured by increased plasma histamine level after vancomycin administration. This, however, would suggest that patients are demonstrating an allergy to vancomycin. A minority of patients may have true allergic reactions, as evidenced by reactions of greater intensity upon subsequent exposure to vancomycin. However, the etiology observed for the majority of patients suggests that RMS is not a true allergic reaction, i.e., RMS is not an IgE induced histamine release from mast cells. The reactions associated with RMS are not dependent on the duration of therapy; they may occur anytime during the infusion, and even occur for patients that have previously tolerated numerous doses of vancomycin. Patients can be re-administered vancomycin once the symptoms resolve, albeit at a slower rate. Therefore, the etiology of RMS is thought to be due to a non-immune related release of histamine, as histamine plasma concentrations increase after the administration of vancomycin.  
      Dosing of vancomycin by infusion, and the concomitant need to actively monitor the side-effect profile, requires constant attention by the nursing staff. Therefore, the administration of vancomycin is complicated in an outpatient setting. A composition that allows for the bolus injection of vancomycin without phlebitis or Redman Syndrome is an unmet medical need.  
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       FIG. 1  is a graph showing the separation of histamine from vancomycin using anion exchange chromatography. Vancomycin was monitored by absorbance at 280 nm. Fractions were collected and assayed for histamine using an ELISA.  
       FIG. 2  is a graph showing the separation of histamine from vancomycin using an anti-histamine affinity column. Vancomycin was monitored by absorbance at 280 nm. Fractions were collected and assayed for histamine using an ELISA.  
       FIG. 3  is a graph showing the separation of histamine from vancomycin using an anti-histamine affinity column. Vancomycin was monitored by absorbance at 280 nm. Fractions were collected and assayed histamine using an ELISA.  
       FIG. 4  shows the results of the determination of histamine in vancomycin samples using HPLC separation followed by mass spectrometry/mass spectrometry (MS/MS). 
    
    
     DETAILED DESCRIPTION  
      As used herein, the singular forms “a,” “an”, and “the” include plural referents unless the context clearly dictates otherwise.  
      Vancomycin is a fermentation product of  Amycolatopsis orientalis . It is possible that histamine or histamine-like compounds are present in the fermentation process. If so, a process that reduces the levels of these compounds, and use of appropriate control limits for these compounds, could reduce or eliminate vancomycin side-effects. Pharmaceutical formulations of vancomycin with a reduced amount of histamine, or formulations of vancomycin that prevent or control the release of histamine from the formulation into the bloodstream, offer the advantages of a bolus injection with fewer side-effects, reduced nursing care, less morbidity and mortality, easier use in an outpatient setting, and the possibility of higher and/or faster dosing.  
      Vancomycin is produced by cultivating the bacteria  A. orientalis  in a nutrient culture media. The histamine or histamine-like compounds may be related to components present in the fermentation broth. Also, it is possible that intermediates of the vancomycin pathway or degradants of vancomycin are histamine-like. Histamine, phenylethylamine, tyramine, tryptamine, dopamine, and serotonin (5-hydroxytryptamine) are vasodialators or vasoactive compounds. Each of these compounds are derivatives of hydrophobic amino acids, ring structures with one or two rings, and planar in nature. Given that vancomycin is a glycopeptide built from hydrophobic amino acids, these vasoactive compounds may be intermediates or by-products of the synthetic pathway. Metal-induced or enzymatic catalysis could produce these compounds from vancomycin and represent vasoactive degradation products. The structure of vancomycin supports this hypothesis.  
      In a well characterized production process for vancomycin, the vancomycin fermentation broth is filtered and added to a column containing an adsorbent resin that decolorizes and desalts the vancomycin. The resin is washed, and the vancomycin is eluted with a solvent of low pH, followed by decolorization with carbon. The vancomycin eluant is then further purified using a crystallization step at low pH. The crystallized vancomycin is combined with a strong acid such as hydrochloric acid (HCl), and then precipitated in an organic solvent such as acetone to form vancomycin HCl. This process for the manufacture and purification of vancomycin HCl is disclosed in U.S. Pat. No. 3,067,099 to McCormick et al., which is incorporated its entirety by reference herein.  
      Typically, the desired vancomycin B is separated from vancomycin-related compounds and other impurities by elution of vancomycin broth through the absorbent column. Various resins are known to be selective for Vancomycin B. For example, DOWEX 50 WX2, a cation-exchange resin available from Dow Chemical, and AMBERLITE XAD- 16, a non-functional resin available from Rohm &amp; Haas, and others, have been utilized to separate vancomycin B from vancomycin-related compounds and impurities.  
      During the production of vancomycin, eluant from the columns is collected in fractions. Each fraction is analyzed to determine the concentration and quantity of vancomycin B. In this way, the fractions with the greatest concentration of vancomycin B can be combined to optimize the yield from the process. The purity of the vancomycin varies from fraction to fraction and depends on a number of factors such as the solvent used to elute the vancomycin from the column and the fermentation medium. In one method of the production of vancomycin described in U.S. Pat. No. 5,258,495, which is incorporated herein by reference in its entirety, the selected vancomycin eluate(s) is combined with an ammonium chloride solution to obtain a solution having a pH of about 2.0 to about 3.5. The solution is then crystallized before being redissolved in a basic solution. An acid is again added to the vancomycin before a final crystallization step.  
      Vancomycin for parenteral administration is provided in a lyophilized form, which is reconstituted at the time of administration with sterile water. The lyophilized product is reconstituted with 20 mL of water for every gram of vancomycin and then subsequently diluted in sterile saline or dextrose solutions for infusion. Dosage for vancomycin for parenteral administration is generally 2 grams per day divided as either 500 milligrams every 6 hours, or 1 gram every 12 hours. To avoid side effects, such as RMS, phlebitis and hypotension, infusion rates of no more than 10 milligrams per minute for adult patients with normal renal function are recommended. Each dose is administered over the course of at least sixty minutes. Two hour infusions are more typical.  
      Vancomycin from manufacturers representing over 50% of the worldwide market and over 80% of the US market were analyzed for the presence of histamine. Lot testing included results from various bulk drug vendors as well as finished dosage forms. As shown in Table 1, each of these products contained over 40 nM histamine in the reconstituted formula.  
                               TABLE 1                                           Histamine           Vanco Lot   Vendor   (nM)                          953963A   A   43.35           041109   B   56.43           041110   B   63.08           041111   B   67.47           041205   B   63.65           041206   B   65.62           041207   B   73.42           WM15082   C   67.27           933203A   A   55.69           A3230596   D   53.57           A3230605   D   47.58           A3230607   D   54.26           040706   E   56.16           040602   E   53.29           040511   E   51.30           895003A   A   47.00           895003A   A   58.80           895003A   A   54.47                      
 
      In each of these analyses, commercial samples of vancomycin were reconstituted according to the label at 50 mg/mL. Bulk drug samples were reconstituted in sterile water at 50 mg/mL. Samples were tested using the Histamine EIA Kit from SPIBio (Massy Cedex, France) according to the directions of the manufacturer.  
      The histamine concentration found in each of the samples is known to be biologically active by the oral route in sensitive individuals (i.e., &gt;5 nM). Activity would be expected to be greater by the injection route, where the histamine is theoretically 100% bioavailable, and likely sufficiently active to cause a histamine response in normal individuals. None of the manufacturers of these commercial samples have previously reported that histamine is present in vancomycin. The realization that histamine is present in these samples allows for the preparation of a formulation that does cause many of the side effects that may be due to the histamine present in the formulations.  
      Ordinary analytical procedures used during the vancomycin purification process have not detected histamine for several reasons. For instance, histamine does not have a strong chromophore and is not observed by UV spectroscopy typically used to monitor the vancomycin purification process. Also, vancomycin presents a complex chromatographic profile due to numerous related compounds. Any histamine peak in the profile may be masked or associated with a different impurity. Indeed, histamine concentrations are extremely low from the perspective of chemical detection. Therefore, the presence of histamine in vancomycin products could easily be overlooked at the levels present in vancomycin.  
      In one aspect, the invention is directed to a pharmaceutical composition including vancomycin that is substantially free of histamine. Substantially free means that the amount of histamine in the composition does not produce the unwanted, histamine-related side effects associated with the administration of vancomycin, including phlebitis, RMS and low blood pressure. In various aspects of the invention, the pharmaceutical composition includes vancomycin and less than 40 nM histamine, or less than 30 mM, 20 nM, and 10 nM histamine in vancomycin when reconstituted from a lyophilized powder to provide a solution of one gram of vancomycin per 20 mL of solution. In one aspect, the invention is directed to a vancomycin formulation having less than about 0.90 nanogram histamine per milligram of vancomycin. For example, no more than about than 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, 0.20 or 0.10 nanogram histamine per milligram of vancomycin.  
      In another aspect, the invention is directed to a pharmaceutical composition of a vancomycin that has been treated to remove histamine. Histamine can be removed from vancomycin by any number of ways known to those of skill in the art of pharmaceutical purification, including gel filtration, ion exchange (cation or anion) exchange chromatography, affinity chromatography, immunoaffinity chromatography, and crystallization processes. While one or more of these methods, and usually cation exchange chromatography and crystallization, is presently used for purification of commercial preparations of vancomycin, the process has not been controlled to remove histamine to a level that it is not physiologically significant in patients receiving vancomycin.  
      Histamine can be removed from vancomycin by loading a vancomycin product on an anion exchange column, and eluting the histamine separate from vancomycin. In particular, a column that is a strong anion exchanger used with a linear gradient of a basic buffer and an acid buffer. For example, 0.25 M ammonium hydroxide and 1 N acetic acid will separate histamine from vancomycin on a strong anion exchange column; the vancomycin will bind to the column under basic conditions while the histamine can be eluted. Acid conditions will elute the vancomycin to provide a clear separation of the two compounds. In the alternative, conditions can be adjusted that the histamine binds the column and the vancomycin is eluted first. Lower strength anion exchange and cation exchange columns may also be suitable but may be less efficient depending upon the histamine load and the separation capabilities.  
      Immunoaffinity chromatography is also suitable for removing histamine from vancomycin. Anti-histamine antibody (IgG) when coupled to a suitable column will bind the histamine and not the vancomycin. After vancomycin is washed from the column, histamine can be eluted with a suitable solvent.  
      In addition, under the appropriate conditions, gel filtration, amino-affinity columns, and crystallization are all techniques that can be used to separate histamine from vancomycin. Gel filtration conditions should account for the relatively small size of vancomycin.  
      In another aspect, the invention is directed to a method for treating a patient suffering from a condition treatable with vancomycin. The method includes administering to the patient an effective amount of the pharmaceutical composition of vancomycin that has a reduced amount of histamine. While vancomycin is typically reserved as an antibiotic of last resort to prevent the development of vancomycin resistant bacterial strains, vancomycin is an effective antibiotic against a variety of infections, as is well documented in the literature. Most commonly, vancomycin is used to treat infections caused by Methicillin Resistant  Staphylococcus aureus  (MRSA) or Methicillan Sensitive  S. aureus  (MSSA). Use of vancomycin is increasingly important due to the emergence of bacterial strains with multiple antibiotic resistances. The ability to bolus inject would substantially reduce the patient burden for the nursing staff.  
      In another aspect, the invention is directed to a method for reducing the histamine related side-effects associated with administration of vancomycin. These side effects are well documented, and include phlebitis at an infusion site, blood pressure drop, and RMS. The administration of a vancomycin having a reduced amount of histamine can reduce or prevent these side effects.  
      In another aspect, the invention is directed to a mutant bacterial microorganism comprising  Amycolatopsis orientalis  lacking a functional gene for histidine decarboxylase. Because histamine is the product of the removal of the carboxyl group on histidine, it is expected that this organism lacking the histidine decarboxylase gene will produce vancomycin without producing histamine. Also, natural variants of  Amycolatopsis orientalis  may be found that produce vancomycin but not histamine.  
      Accordingly, the invention provides a so-called “knockout” recombinant genetic bacterial strain of  Amycolatopsis orientalis  having a defective, most preferably a deleted, DNA sequences encoding the histidine decarboxylase gene. The knock-out organism can be created by replacing the functional histidine decarboxylase DNA sequence with a construct having a defective or deleted coding sequence, additional homologous sequences 5′ and 3′ from the defective coding sequences, and selectable markers for selecting clones of cells bearing the construct. Such selectable markers can be any known selectable gene, such as the genes for neomycin resistance, hygromycin resistance, the guanine phosphotransferase gene of  E. coli  (Ecogpt) and others known in the art. These constructs of the invention are provided to maximize the likelihood that recombinant cells will incorporate the construct DNA into host cell genomic DNA by homologous recombination that disrupts the histidine dehydrogenase gene.  
      Also contemplated is the isolated polynucleotide sequence of the  Amycolatopsis orientalis  histidine decarboxylase gene, and fragments thereof.  
      In one aspect the invention is directed to a method for producing vancomycin by fermenting  Amycolatopsis orientalis  lacking the histidine decarboxylase gene collecting vancomycin secreted from the microorganism. Fermentation may be conducted by known methods, or the medium may be adjusted to supplement the organism to ensure growth in the absence of the organism&#39;s ability to produce histamine.  
      In another aspect, the invention is directed to a pharmaceutical composition comprising a time-released formulation of vancomycin. In this aspect, the vancomycin can be administered by intravenous injection more quickly than the present indication of no more than 10 milligrams per minute, but the release of vancomycin and histamine from the formulation to the bloodstream would be sustained over a much longer period of time. The control of histamine release would result in plasma concentrations no more than that observed by infusion of vancomycin. Preferably, the histamine release profile will result in plasma concentrations that are less than that observed by typical infusion rates of currently available vancomycin. Accordingly, the histamine related side effects associated with the administration of vancomycin can be reduced, ameliorated, or prevented because the sustained release of vancomycin and histamine from the formulation would be similar to the slow intravenous administration of vancomycin as presently formulated. For example, with a sustained release formulation of vancomycin, patients can be administered a full dose of vancomycin by infusion of vancomycin at rates of greater than 10 milligrams per minute, but the release of vancomycin from the formulation into the blood stream can be controlled to less than 10 milligrams per minute, for example 9, 8, 7, 6, 5, 4, 3, 2, and 1 milligrams per minute. More importantly, the formulation releases histamine at less than 9 nanograms per minute, for example no more than 8, 7, 6, 5, 4, 3, 2, or 1 nanograms per minute. Preferably, the formulation does not release any histamine into the bloodstream. In one aspect, vancomycin is released faster than 10 milligrams per minute, but histamine is released at less than 9 nanograms per minute.  
      Controlled release formulations of vancomycin include oil and water emulsions, micelles, and lipsomal formulations. For example, vancomycin can be emulsified with a non-ionic surfactant, such as TWEEN®, whereby the vancomycin is incorporated into the detergent micelle. An example of an oil and water emulsion includes a non-pyrogenic vegetable oil (10-50%), egg phosphatides added as an emulsifier (up to 5%), and glycerin (up to 5%) in water for injection. Sodium hydroxide may be added for pH adjustment, preferably between about 6.0 to 9.0.  
      In another aspect, the invention is related to a liposomal formulation of vancomycin that allows for the controlled release of histamine that may be present in the vancomycin formulation. Emulsions, liposomes, or other lipid based delivery systems can be formulated for parenteral administration. These formulations are advantageous due to their ability to provide for a controlled release of the drug while being compatible with the intravenous environment.  
      The lipids used in the compositions of the present invention can be synthetic, semi-synthetic or naturally-occurring lipids, including phospholipids, tocopherols, steroids, fatty acids, glycoproteins such as albumin, negatively-charged lipids and cationic lipids. Phosholipids include egg phosphatidylcholine (EPC), egg phosphatidylglycerol (EPG), egg phosphatidylinositol (EPI), egg phosphatidylserine (EPS), phosphatidylethanolamine (EPE), and egg phosphatidic acid (EPA); the soya counterparts, soy phosphatidylcholine (SPC); SPG, SPS, SPI, SPE, and SPA; the hydrogenated egg and soya counterparts (e.g., HEPC, HSPC), other phospholipids made up of ester linkages of fatty acids in the 2 and 3 of glycerol positions containing chains of 12 to 26 carbon atoms and different head groups in the 1 position of glycerol that include choline, glycerol, inositol, serine, ethanolamine, as well as the corresponding phosphatidic acids. The chains on these fatty acids can be saturated or unsaturated, and the phospholipid can be made up of fatty acids of different chain lengths and different degrees of unsaturation. In particular, the compositions of the formulations can include dipalmitoylphosphatidylcholine (DPPC), a major constituent of naturally-occurring lung surfactant as well as dioleoylphosphatidylcholine (DOPC). Other examples include dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylglycerol (DMPG) dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) distearoylphosphatidylcholine (DSPC) and distearoylphosphatidylglycerol (DSPG), dioleylphosphatidylethanolamine (DOPE) and mixed phospholipids like palmitoylstearoylphosphatidylcholine (PSPC) and palmitoylstearoylphosphatidylglycerol (PSPG), triacylglycerol, diacylglycerol, seranide, sphingosine, sphingomyelin and single acylated phospholipids like mono-oleoyl-phosphatidylethanolamine (MOPE).  
      The lipids used can include ammonium salts of fatty acids, phospholipids, and glycerides, steroids, phosphatidylglycerols (PGs), phosphatidic acids (PAs), phosphotidylcholines (PCs), phosphatidylinositols (Pls) and the phosphatidylserines (PSs). The fatty acids include fatty acids of carbon chain lengths of 12 to 26 carbon atoms that are either saturated or unsaturated. Some specific examples include: myristylamine, palmitylamine, laurylamine and stearylamine, dilauroyl ethylphosphocholine (DLEP), dimyristoyl ethylphosphocholine (DMEP), dipalmitoyl ethylphosphocholine (DPEP) and distearoyl ethylphosphocholine (DSEP), N-(2,3-di-(9(Z)-octadecenyloxy)-prop-1-yl-N,-N,N-trimethylammonium chloride (DOTMA) and 1,2-bis(oleoyloxy)-3-(trimethyl-ammonio)propane (DOTAP). Examples of steroids include cholesterol and ergosterol. Examples of PGs, PAs, PIs, PCs and PSs include DMPG, DPPG, DSPG, DMPA, DPPA, DSPA, DMPI, DPPI, DSPI, DMPS, DPPS and DSPS, DSPC, DPPC, DMPC, DOPC, egg PC.  
      Liposomes are completely closed lipid bilayer membranes containing an entrapped aqueous volume. Liposomes can be unilamellar vesicles (possessing a single membrane bilayer) or multilamellar vesicles (onion-like structures characterized by multiple membrane bilayers, each separated from the next by an aqueous layer). The bilayer is composed of two lipid monolayers having a hydrophobic “tail” region and a hydrophilic “head” region. The structure of the membrane bilayer is such that the hydrophobic (nonpolar) “tails” of the lipid monolayers orient toward the center of the bilayer while the hydrophilic “heads” orient towards the aqueous phase. Lipid complexes are associations between lipid and the anti-infective agent that is being incorporated. This association can be covalent, ionic, electrostatic, noncovalent, or steric. These complexes are non-liposomal and are incapable of entrapping additional water soluble solutes. In a particular example, an intravenous formulation may contain a sterile, non-pyrogenic lyophilized product for intravenous infusion supplied in quantities of 50 mg of vancomycin intercalated into a liposomal membrane consisting of approximately 213 mg hydrogenated soy phosphatidylcholine; 52 mg cholesterol, NF; 84 mg distearoylphosphatidylglycerol; 0.64 mg alpha tocopherol, USP; together with 900 mg sucrose, NF; and 27 mg disodium succinate hexahydrate as buffer. Following reconstitution with Sterile Water for Injection, USP, the resulting pH of the suspension is between 5-6.  
      In another aspect, the invention is related to a growth media having a reduced amount of histamine relative to conventional media, and that supports growth of  Amycolatopsis orientalis  and the fermentation of vancomycin. Regardless of the media, manufacturing specifications can be provided to ensure vancomycin formulations are produced and tested to ensure that the formulation has less than 40nM histamine.  
      The following are provided for exemplification purposes only and are not intended to limit the scope of the invention described in broad terms above. All references cited in this disclosure are incorporated herein by reference.  
     EXAMPLES  
     Example 1  
     Chromatographic Separation of Histamine from Vancomycin  
      Vancomycin (Hospira, Inc.) was reconstituted at 50 mg/mL per the label directions and then adjusted to 0.25 M ammonium hydroxide using a 1 M stock solution. A 5 mL HighQ column (BioRad), a strong anion exchanger, was installed on the Biologic DuoFlow chromatography system and equilibrated with 0.25 M ammonium hydroxide mobile phase. Vancomycin was loaded onto the column via a 1 mL injection loop and the column was washed with a 30 mL isocratic step at a flow rate of 2.5 mL/minute. Vancomycin was then eluted with a 35 mL linear gradient of 0.25 M ammonium hydroxide to 1 N acetic acid. UV (A 280 nm ), pH and conductivity were monitored during the chromatography. Column fractions (2.5 mL) were assayed for histamine by ELISA (SPI-Bio) and vancomycin by UW.  FIG. 1  confirmed the presence of histamine in vancomycin samples and demonstrated that chromatographic separation of vancomycin (fractions 21-22) and histamine (fractions 4-5) was possible. The acetic acid interfered with histamine ELISA&#39;s starting at fraction 21. Fractions 21 and 22 demonstrated less than 10 nM histamine when pH was adjusted above pH 7.  
     Example 2  
     Anti-Histamine Affinity Column Chromatography  
      Anti-histamine rabbit antibody (Sigma) was coupled to Affi-Gel Hz resin (BioRad) per the kit instructions. A 2 mL column contained approximately 0.47 mg of anti-histamine antibody. The column was equilibrated with five volumes of 10 mM HEPES (pH 7.0) buffer.  
      Vancomycin was reconstituted at 50 mg/mL in HEPES buffer and a 2 mL aliquot was loaded onto the column. The column was washed with one volume of HEPES buffer containing 0.5 M sodium chloride followed with two volumes of HEPES buffer. The bound histamine was then eluted with 2 volumes of 0.1 N acetic acid. Fractions (0.5 mL) were collected and then assayed by UV and ELISA.  FIG. 2  shows the presence of antibody bound histamine. The residual histamine in the vancomycin peak likely resulted from overloading of the column. The vancomycin peak fractions were combined and run a second time on the anti-histamine affinity column. As shown in  FIG. 3 , these results showed that vancomycin peak lacked histamine and that the additional histamine present in the initial material was separated from the vancomycin.  
     Example 3  
     Determination of Histamine by Mass Spectroscopy  
      Fractions representing the histamine peak from multiple runs of the HighQ column as in Example 1 were collected, lyophilized, and reconstituted in small volume of water. Chromatographic separation was accomplished using gradient high-performance liquid chromatography. The liquid chromatograph (Thermo Finnigan Surveyor) was operated at 1.0 mL/min with the following gradient profile:  
                                       Time (minutes)   % Mobile Phase A   % Mobile Phase B                                            0   100   0       12.0   0   100       16.0   0   100       16.8   100   0       24.0   100   0                  
 
      Mobile Phase A was prepared by mixing 50 mL of HPLC grade water (Burdick and Jackson) with 950 mL of acetonitrile (EMD). Mobile Phase B was prepared by mixing 670 mL of 12.5 mM ammonium acetate (EM Science), 0.72 mL of glacial acetic acid (EMD) and 330 mL of acetonitrile. Both mobile phases were degassed using an inline vacuum degasser. The chromatography column was a Hypersil APS-2, 150×3 mm with 3-micron particle size. The column temperature was maintained at 60 degrees Celsius. The injection volume was 100 microliters. Authentic samples of histamine were prepared by dissolving histamine dihydrochloride (Fluka) in HPLC grade water, and diluting.  
      A triple quadrupole mass spectrometer (Thermo Finnigan Quantum Ultra) was used in single reaction monitoring mode (SRM) to monitor the transition from m/z 112 to m/z 95 (loss of neutral ammonia from protonated histamine) with positive ion electrospray ionization. As shown in  FIG. 4 , a peak was observed after about 7.79 minutes having a mass of 95.2. This peak was consistent with the retention time and mass observed with histamine dihydrochloride standards run under the same conditions (data not shown). Thus, the data confirmed the ELISA results indicating that histamine is present in vancomycin. Histamine was concentrated 5- to 10-fold for chemical detection as compared to the concentrations necessary for detection by ELISA.  
      Although various specific embodiments of the present invention have been described herein, it is to be understood that the invention is not limited to those precise embodiments and that various changes or modifications can be affected therein by one skilled in the art without departing from the scope and spirit of the invention.