Abstract:
A packaged pharmaceutical product having extended shelf life includes a pharmaceutical preparation and a dispensing container. The container has a hollow body, having an open end therein, and is formed from a blend of low density polyethylene, having high permeability of label-related extractables, and a polypropylene, having low permeability of label-related extractables. A body wall thickness enables both drop-by-drop dispensing of the pharmaceutical preparation by manual squeezing of the body, and, in combination with the blend of polymers, prevents significant ingress of label-related extractables through the body wall upon storage of the container with the body filled with the pharmaceutical preparation. A dropper tip fixed to the body open end is provided for forming droplets of pharmaceutical preparation upon manual squeezing of the body.

Description:
The present application is a continuation-in-part of U.S. Ser. No. 08/398,557, filed Mar. 3, 1995, now U.S. Pat. No. 5,609,273. 
    
    
     The present invention is generally directed to packaging and, more specifically, directed to a packaged pharmaceutical product and a method of packaging. 
     Many pharmaceutical preparations, including those for ophthalmic use, utilize chlorobutanol, which is a widely used anti-microbial preservative which is added to numerous pharmaceutical preparations, as well as being an active ingredient in certain oral sedatives and topical anesthetics. 
     When used as a preservative, the concentration of chlorobutanol in the pharmaceutical preparation is preferably above about 0.3% W/V of the pharmaceutical preparation. Such concentrations enable storage of the pharmaceutical preparation for periods of time of up to 18 or 24 months or more. Certain pharmaceutical preparations, such as ophthalmic preparations, are limited in the amount acceptable of chlorobutanol therein to no more than about 0.5% W/V in view of the cytotoxicity of this agent. 
     While squeezable containers are presently used for storage of pharmaceutical preparations comprising chlorobutanol, such storage systems, in view of the permeability of chlorobutanol through commonly used low density polyethylene containers, have now been found to be inadequate because of loss of chlorobutanol through the polyethylene. 
     With particular reference to pharmaceutical preparations which need to be dispensed on a drop-by-drop basis, the most suitable packaging is a squeezable container. Heretofore, rigid containers, such as glass and non-permeable plastics, have been utilized in conjunction with an eye dropper type dispenser; however, this arrangement leads to non-sterile conditions due to exposure of the preparation to the atmosphere. 
     A further complication with regard to the storage of pharmaceutical preparations utilizing chlorobutanol is the fact that the pH of the pharmaceutical preparation goes down, i.e., becomes more acid, upon storage in a container having an absolute barrier to chlorobutanol due to the change of pH of the pharmaceutical preparation over a long shelf life. In addition, a glass container requires an additional eye dropper type dispenser for proper utilization by a patient using the pharmaceutical preparation. 
     It should be evident that the container for the pharmaceutical preparation is the most important part of the packaged pharmaceutical product in that it contacts the pharmaceutical preparation most extensively over a long period of time, particularly in the warehousing thereof prior to sale, and in the user&#39;s home prior to complete use of the pharmaceutical preparation which is dispensed on a drop-by-drop basis as needed. 
     Typical user-friendly containers, or dispensers, or bottles, for pharmaceutical preparations, are formed from polyethylene, which in most instances provide a suitable combination with a pharmaceutical preparation which results in a packaged pharmaceutical product that is user-friendly for dispensing of the pharmaceutical preparation on a drop-by-drop basis. 
     However, if the pharmaceutical preparation includes chlorobutanol as a preservative, a complex problem is introduced. Specifically, polyethylene is permeable by chlorobutanol and therefore, upon storage, chlorobutanol permeates the container wall and evaporates, reducing the concentration in the preparation. Accordingly, its preservative value to the pharmaceutical preparation is diminished. This phenomenon occurs over a matter of days, depending on the storage temperature. As hereinabove noted, a generally accepted upper limit for the amount of chlorobutanol in an ophthalmic pharmaceutical preparation is about 0.5% W/V. It should also be appreciated that the lower specification for an acceptable amount of preservative, such as chlorobutanol, may be 0.3% W/V (European requirement) or 0.2% W/V (U.S. requirement). If the chlorobutanol content in a pharmaceutical preparation is reduced by about 40% due to loss through a container wall, the pharmaceutical preparation no longer meets preservative specifications. As hereinabove mentioned, this can occur in a matter of days if the container is formed from 100% polyethylene. 
     Other materials suitable for containing a pharmaceutical preparation preserved with chlorobutanol include polypropylene, among other polymers. However, while these resins are suitable for preventing the migration of chlorobutanol therethrough, they, because of their modulus of elasticity, cannot be used in a user-friendly, i.e., squeezable, container. 
     Importantly, it has further been found that the combination, or blend, of both the polyethylene and polypropylene is effective in preventing substantial ingress through containers of label-related extractables such as adhesives, inks, varnishes, and curing agents. That is, when labels are placed on the outside of a product container made up of permeable plastic material (typically, low density polyethylene (LDPE)), extractable components from the label system may migrate from the label through the bottle wall and into the product matrix. The appearance of extractable components in the product matrix raises concern from several perspectives, including toxicity and patient exposure, and possible reduction of product stability due to interaction with formulation ingredients. This is particularly true when benzalkonium chloride is utilized as a preservative. 
     Therefore, there is need for a packaged pharmaceutical product and method that provides for a user-friendly squeezable container for pharmaceutical preparations which can prevent ingress of label related extractables through the container walls. 
     SUMMARY OF THE INVENTION 
     A packaged pharmaceutical product having extended shelf life in accordance with the present invention generally includes a pharmaceutical preparation comprising chlorobutanol. More specifically, the pharmaceutical preparation may include chlorobutanol up to 0.5% W/V to insure its preservative activity. 
     In addition, a dispensing container is provided which includes a hollow body, having an open end thereon, formed from a blend of low density polyethylene and polypropylene. The low density polyethylene, while suitable for forming a squeezable container, includes a high chlorobutanol permeability. This high chlorobutanol permeability is compared to the chlorobutanol permeability of polypropylene which, in comparison, is very low. However, polypropylene is not suitable for forming a user-friendly, or squeezable, container in small sized, for example, 10 ml bottles as are typically utilized in the ophthalmic field. 
     In addition, a body wall thickness provides a means for both enabling drop-by-drop dispensing of the pharmaceutical preparation by manual squeezing of the body and, in combination with the blend of polymers, preventing ingress of label related extractables through the body wall upon storage of the container. 
     Finally, dropper tip means are provided and fixed to the body open end for forming droplets of pharmaceutical preparation upon manual squeezing of the body. 
     More particularly, the dispensing container according to the present invention includes a blend of polymers comprising between about 50% and about 75% polypropylene by weight and between about 50% and 25% polyethylene by weight. 
     More specifically, it has been found that a blend of about 60% polypropylene and about 40% polyethylene provides for a squeezable container body, while at the same time providing a satisfactory barrier for the passage of label related extractables therethrough so that long-term storage can be effected interaction of such label related extractables with a pharmaceutical preparation in the container. 
     Still more particularly, it has been found that a polypropylene best suited for blending with polyethylene is one having a flexural modulus of about 120,000 PSI. Using this blend, it has been found that an effective wall thickness for providing both squeezability and a barrier to the passage of label related extractables is between about 0.018&#34; (0.46 mm) and 0.032&#34; (0.81 mm). As part of the packaged pharmaceutical product, both define the present invention as also directed to a dispensing container for dropwise dispensing of a pharmaceutical preparation which includes chlorobutanol as a preservative. The body is provided with an open end therein, with the body being formed from a blend of low density polyethylene, having high chlorobutanol permeability, and a polypropylene having low chlorobutanol permeability. 
     A body wall thickness is determined for both enabling drop-by-drop dispensing of the pharmaceutical preparation by manual squeezing of the body and, in combination with the blend of polymers, preventing significant ingress of label related extractables through the body wall upon storage of the container with the body filled with the pharmaceutical preparation. In addition, a sealable dropper tip is provided which provides means for forming droplets of pharmaceutical preparation upon squeezing of the body. 
     This invention also encompasses a method of packaging a pharmaceutical preparation which includes forming a container from a resin blend of polypropylene and a low density polyethylene with a wall thickness enabling drop-by-drop dispensing of the pharmaceutical preparation by manual squeezing of the container. At the same time, storage of the pharmaceutical preparation for a period of at least 200 days at about 25° C., is enabled without loss of more than 40% of the original amount of chlorobutanol through the wall of a container or ingress of label related extractables. When an original amount of about 0.5% W/V chlorobutanol is present in the pharmaceutical preparation, extended shelf-life storage is enabled without the chlorobutanol content of the pharmaceutical preparation falling below about 0.3% W/V. 
     Further steps in accordance with the present invention include filling the container with the pharmaceutical preparation and providing a sealable dropper tip for enabling drop-by-drop dispensing of the pharmaceutical preparation from the container. 
     As hereinabove noted, the present invention also encompasses a packaged pharmaceutical product comprising benzalkonium chloride in which the dispensing container includes a label and is comprised of a hollow body having an open end therein formed from a blend of low density polyethylene having high permeability of label-related extractables and polypropylene having low permeability of label-related extractables. 
     As in the embodiment hereinabove described, means are provided which define a body wall thickness for both enabling drop-by-drop dispensing of the pharmaceutical preparation by manual squeezing of the body, and, in combination with the blend of polymers, preventing significant ingress of the label-related extractables through the body wall upon storage of the container with the body filled with the pharmaceutical preparation. Dropper tip means are provided in fixed open body end performing droplets of pharmaceutical preparation upon manual squeezing of the body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages and features of the present invention will be better understood by the following description when considered in conjunction with the accompanying drawings in which: 
     FIG. 1 is a plot of the amount of chlorobutanol remaining with time in a pharmaceutical preparation while stored at 45° C. in a 10 ml container as a function of a blend of polyethylene and a polypropylene having a flexural modulus of 120,000 PSI; 
     FIG. 2 is similar to the part shown in FIG. 1 with the blend of polymers being polyethylene and a polypropylene having a flexural modulus of 145,000 PSI; 
     FIG. 3 corresponds to the blends of polymers shown in FIG. 1 when stored at 25° C.; 
     FIG. 4 corresponds to the blends of polymers shown in FIG. 2 stored at 25° C.; 
     FIG. 5 is a plot of both rate constant and time in days to reach 60% of original chlorobutanol in the pharmaceutical product as a function of the amount of polypropylene in the resin for a polypropylene having a flexural modulus of 120,000 PSI and 145,000 PSI, all at a storage temperature of 25° C.; 
     FIG. 6 is similar to the plot shown in FIG. 5 with the storage temperature being 45° C.; 
     FIG. 7 is a view of a dispensing container in accordance with the present invention as it may be used; 
     FIG. 8 includes benzalkonium chloride HPLC chromatograms for test formulations stored in glass ampules at 45° C. (run 1, control); 
     FIG. 9 includes benzalkonium chloride HPLC chromatograms for the test formulation stored in unlabeled LDPE bottles at 45° C. (run 2, control); 
     FIG. 10 includes benzalkonium chloride HPLC chromatograms for the test formulation stored in labeled LDPE bottles at 45° C. (run 3); 
     FIG. 11 shows benzalkonium chloride HPLC chromatograms for the test formulation stored in unlabeled PP/LDPE blended bottles at 45° C. (run 4, control); 
     FIG. 12 shows benzalkonium chloride HPLC chromatograms for the test formulation stored in labeled PP/LDPE blended bottles at 45° C. (run 5); 
     FIG. 13 shows levobunolol HPLC chromatograms for the test formulation stored in glass ampules at 45° C.; 
     FIG. 14 shows levobunolol HPLC chromatograms for the test formulation stored in unlabeled LDPE bottles at 45° C.; 
     FIG. 15 shows levobunolol HPLC chromatograms for the test formulation stored in labeled LDPE bottles at 45° C.; and 
     FIG. 16 shows levobunolol HPLC chromatograms for the test formulation stored in labeled PP/LDPE blended bottles at 45° C. 
    
    
     DETAILED DESCRIPTION 
     Any suitable pharmaceutical preparation may be incorporated into the present invention and particularly ophthalmic preparations suitable for a dropwise dispensing in an eye. As a specific example of such a preparation as a wetting solution which may include polyvinyl alcohol with hydroxypypropyl methylcellulose, edetate disodium, sodium chloride, potassium chloride, with chlorobutanol being added as a preservative in an original amount of 0.5% W/V. This pharmaceutical preparation is presented here by example only, for the purpose of defining the present invention. The characteristics of the present invention, which includes a packaged pharmaceutical product, is shown in FIGS. 1-6, as hereinafter described. 
     With reference to FIG. 7, there is shown a packaged pharmaceutical product 10 which includes a dispensing container 12, having a hollow body 14, with an end 16 having an opening 18 thereon, to which is fixed a dropper tip 20 which provides means for forming droplets of pharmaceutical preparation upon manual squeezing of the body 14, for example, a thumb 22 and forefinger 24 of a hand 26. 
     As hereinabove noted, the present invention provides a packaged pharmaceutical product which has a longer shelf life than heretofore possible utilizing a pharmaceutical preparation having chlorobutanol therein and a squeezable container. As noted, the container 12 is the most important part of the packaging in that it contacts the pharmaceutical preparation (not shown) and thus must provide a barrier to the permeation of chlorobutanol therethrough. 
     The formation of the container 12, as also hereinabove noted, may be through blow molding, or the like, or in a conventional technique; however, the polymer from which the container is formed is of utmost importance. 
     Materials, such as polypropylene, which are known to provide barrier properties to the passage of chlorobutanol therethrough, are not suitable for a squeezable container, i.e., as shown in FIG. 7, because of the rigid-like properties of polypropylene. On the other hand, as hereinabove noted, while polyethylene is a resin which can be formed into a container with squeezable properties, no barrier to the passage of chlorobutanol is provided. 
     Still more importantly, it has been found that polypropylene, having a selected modulus of elasticity, also affects the properties of the final blend utilized in the manufacture of the container 12. 
     Specific examples are a polypropylene having a flexural modulus according to ASTM test method D 790 of 145,000 PSI, such as manufactured by Rexene Resins under the product type PP23M2, and a polypropylene having a flexural modulus of 120,000 PSI manufactured by Fina, under the product number 7231X, having differing barrier properties when blended with polyethylene. 
     Because of the difference of flexural modulus, the Rexene polymer is a stiffer and less squeezable resin than that of the Fina resin. 
     FIGS. 1 and 2 show the concentration of chlorobutanol for barrier bottles stored at 45° C. for a Fina blended polymer and a Rexene blended polymer, respectively. Similarly, FIGS. 3 and 4 show the same bottle configuration with the storage temperature being 25° C. 
     FIGS. 5 and 6 show the rate constant and the time and days to reach 60% of the original content of chlorobutanol, i.e., 0.3% W/V, as a function of the amount of polypropylene in the resin at storage temperatures of 25° C. and 45° C., respectively. 
     In FIG. 5, curves 30 and 32 represent a blend of Fina resin and polyethylene and curves 34, 16 represent a Rexene polypropylene blend with polyethylene. Similarly, in FIG. 6, curves 40 and 42 represent a Fina polypropylene/polyethylene blend and curves 44, 46 represent a Rexene polypropylene/polyethylene blend. 
     Squeezability tests of 10 ml bottles formed from the blend of polypropylene and polyethylene (i.e., of the various blends of both Rexene polypropylene/polyethylene and Fina polypropylene/polyethylene) were conducted. Suitable squeezable properties were determined to occur with Rexene polypropylene/polyethylene blends of 50% or less and with Fina polypropylene/polyethylene blends of 75% or less. In these tests, a body wall thickness is between about 0.018&#34; (0.46 mm) and about 0.032&#34; (0.81 mm). Most preferably, the body wall thickness is about 0.025&#34; (0.63 mm). 
     Both resin blends give acceptable chlorobutanol properties at 50% by weight, or more, of polypropylene in the blend. Accordingly, it was determined that the most suitable blend is with the Fina polypropylene, having a flexural modulus of 120,000 PSI and a blend of between approximately up to 50% polypropylene by weight and up to 75% polyethylene by weight, with a target blend ratio of 60% Fina polypropylene by weight and 40% polyethylene by weight. 
     The Rexene polypropylene is not squeezable above percentages of 50% polypropylene by weight in the blend. Below 50% polypropylene by weight, the barrier properties decrease. Therefore, it was determined that polypropylene having a flexural modulus greater than 120,000 PSI is not most suitable for providing a packaged pharmaceutical product in a squeezable bottle of small size (about 10 ml or less). 
     A controlled study was conducted to evaluate the influx barrier properties of 60/40 wt % PP/LDPE blended bottles with a known incompatible product/label combination. The study consisted of five runs in which 10 ml of test formulation (aqueous isotonic solution containing 0.1% levobunolol and 0.0050% benzalkonium chloride (BAK), pH 7.4) was filled into five different container/label configurations as shown in Table I. Sample stability including levobunolol concentration, BAK concentration, pH and osmolality was evaluated for three months under 45° C. storage conditions. Run Nos. 1, 2, and 4 constitute study controls. 
     
                       TABLE I______________________________________Container/Label ConfigurationsRunNo.     Container      Label      Comment______________________________________1       glass ampules  none       control2       LDPE bottle    none       control   (10 ml Boston Round)3       LDPE bottle    commercial incompatible   (10 ml Boston Round)                  label4       PP/LDPE bottle none       control   (10 ml Boston Round)5       PP/LDPE bottle commercial test   (10 ml Boston Round)                  label      configuration______________________________________ 
    
     Results and Discussion 
     Accelerated 45° C. stability data for levobunolol concentration, BAK, pH and osmolality are shown below in Tables II-VI. Zero time assays for all runs were performed four days after date of manufacture and filling with filled samples stored during this time at ambient temperature. Of particular interest are the BAK results which are invariant over the three-month time interval for the glass ampules (Table II), unlabeled LDPE bottles (Table III), and both labeled and unlabeled PP/LDPE blended bottles (Tables V-VI). The BAK data for the labeled LDPE bottles (Table IV) show a significant decline to about 60% of the initial value after the three-month interval. All other stability parameters are unaffected by container/label configuration under these storage conditions. 
     
                       TABLE II______________________________________Stability Results for the Test FormulationPackaged in Glass Ampules Stored at 45° C.ContainerDescription    Glass AmpuleTime Interval    BAK        LBUN            Osm(Months) (% w/v)    (% w/v)   pH    (mOsm/Kg)Specification    0.0043-0.0053               0.090-0.110                         5.8-7.4                               270-350______________________________________0        0.0047     0.096     7.20  282    0.0048     0.098     7.20  277    0.0047     0.095     7.20  2800.5      0.0050     0.100     6.81  --    0.0049     0.100     6.81  288    0.0049     0.100     6.82  --1        0.0049     0.100     6.67  286    0.0049     0.099     6.66  285    0.0049     0.100     6.68  2883        0.0045     0.095     6.20  296    0.0046     0.095     6.20  294    0.0045     0.096     6.20  298______________________________________ 
    
     
                       TABLE III______________________________________Stability Results for the Test FormulationPackaged in Unlabeled LDPE Bottles Stored at 45° C.ContainerDescription    Unlabeled LDPE BottleTime Interval    BAK        LBUN            Osm(Months) (% w/v)    (% w/v)   pH    (mOsm/Kg)Specification    0.0043-0.0053               0.090-0.110                         5.8-7.4                               270-350______________________________________0        0.0046     0.096     7.21  275    0.0047     0.097     7.21  275    0.0047     0.096     7.21  2750.5      0.0050     0.100     6.82  292    0.0050     0.100     6.82  285    0.0050     0.100     6.82  2971        0.0050     0.100     6.68  293    0.0050     0.100     6.65  --    0.0049     0.101     6.68  --3        0.0047     0.097     6.18  299    0.0047     0.096     6.13  299    0.0047     0.097     6.15  303______________________________________ 
    
     
                       TABLE IV______________________________________Stability Results for the Test FormulationPackaged in Labeled LDPE Bottles Stored at 45° C.ContainerDescription    Labeled LDPE BottleTime Interval    BAK        LBUN            Osm(Months) (% w/v)    (% w/v)   pH    (mOsm/Kg)Specification    0.0043-0.0053               0.090--0.110                         5.8-7.4                               270-350______________________________________0        0.0048     0.099     7.21  275    0.0048     0.098     7.20  276    0.0047     0.096     7.21  2730.5      0.0043     0.102     6.79  294    0.0045     0.100     6.79  --    0.0043     0.101     6.79  --1        0.0036     0.100     6.61  290    0.0036     0.100     6.63  --    0.0035     0.101     6.62  2833        0.0029     0.098     6.07  --    0.0029     0.098     6.08  300    0.0028     0.098     6.08  298______________________________________ 
    
     
                       TABLE V______________________________________Stability Results for the Test Formulation Packagedin Unlabeled PP/LDPE Blended Barrier Bottles Stored at 45° C.ContainerDescription    Unlabeled PP/LDPE Blended Barrier BottleTime Interval    BAK        LBUN            Osm(Months) (% w/v)    (% w/v)   pH    (mOsm/Kg)Specification    0.0043-0.0053               0.090-0.110                         5.8-7.4                               270-350______________________________________0        0.0047     0.097     7.21  276    0.0047     0.096     7.20  276    0.0047     0.097     7.21  2780.5      0.0050     0.100     6.82  287    0.0050     0.100     6.82  289    0.0050     0.100     6.81  2891        0.0049     0.100     6.66  287    0.0049     0.100     6.67  --    0.0049     0.100     6.68  --3        0.0046     0.096     6.13  300    0.0047     0.096     6.17  --    0.0047     0.097     6.17  299______________________________________ 
    
     
                       TABLE VI______________________________________Stability Results for the Test Formulation Packagedin Labeled PP/LDPE Blended Barrier Bottles Stored at 45° C.ContainerDescription    Labeled PP/LDPE Blended Barrier BottleTime Interval    BAK        LBUN            Osm(Months) (% w/v)    (% w/v)   pH    (mOsm/Kg)Specification    0.0043-0.0053               0.090-0.110                         5.8-7.4                               270-350______________________________________0        0.0048     0.096     7.21  278    0.0047     0.096     7.20  278    0.0046     0.096     7.20  2790.5      0.0050     0.099     6.84  --    0.0049     0.100     6.84  286    0.0050     0.100     6.82  2901        0.0049     0.101     6.66  288    0.0049     0.100     6.65  284    0.0049     0.101     6.67  2893        0.0047     0.097     6.16  301    0.0047     0.096     6.17  --    0.0046     0.097     6.15  302______________________________________ 
    
     BAK HPLC chromatograms for the initial through three-month time-points are shown in FIGS. 1-5 for the various container/label combinations. Peaks corresponding to the C12 and C14 homologs of BAK are shown in the chromatograms eluting at approximately 4.7 and 6.2 minutes, respectively. The BAK HPLC profiles are stable with time for the glass ampules (FIG. 8), unlabeled LDPE (FIG. 9) and unlabeled and labeled PP/LDPE blended bottles (FIGS. 11 and 12). For labeled LDPE bottles, the BAK level declines from an initial value of 0.0048% to 0.0029% (Table IV) after three months&#39; storage at 45° C., and this is primarily due to a loss of the C14 homolog peak as shown in FIG. 10. In addition, label extractable peaks are observable in the chromatograms for labeled LDPE (FIG. 10) eluting at 2.5-3.5 minutes that do not appear in unlabeled LDPE bottles or in labeled or unlabeled PP/LDBE bottles. Examples of the label-related extractables include but are not limited to, for example: Adhesives, acrylic or rubber based, including acetates, polystyrene, vinyls, polyesters and polyolefins; Photoinitiators, such as benzophenone; Antioxidants such as butylated hydroxytoluene derivatives; UV absorbers such as benzophenone; and Plasticizers such as diethyl phthalate. All of the hereinabove noted components and others are well known in the label art. 
     Levobunolol HPLC chromatograms for initial through three-month time-points are shown in FIGS. 13-16 for the various container/label combinations. The chromatograms for test formulations packaged in glass ampules show a peak eluting at approximately 1.8 minutes corresponding to disodium edetate and a large peak at 4 minutes corresponding to levobunolol (FIG. 13). The disodium edetate peak declines with time as a normal aspect of product aging. The levobunolol HPLC chromatograms for glass ampules (FIG. 13), unlabeled LDPE (FIG. 14) and labeled PP/LDPE blended bottles (FIG. 16) are identical. The levobunolol HPLC chromatogram for labeled LDPE (FIG. 15) displays a label extractable peak co-eluting with the disodium edetate peak at approximately 2 minutes. This peak is not observed in the labeled PP/LDPE chromatograms shown in FIG. 16. 
     Conclusions 
     These data demonstrate the effectiveness of PP/LDPE blended bottles in preventing label-related components from migrating into the product matrix. In the case of the test formulation in LDPE bottles studied here, the appearance of label extractables in product results in a reduction of BAK over time primarily through loss of the C14 homolog. Prevention of inward migration of label-related compounds into the product matrix through the use of PP/LDPE blended bottles has been shown to eliminate the appearance of extractables and subsequent loss of BAK. 
     Although there has been hereinabove described a specific packaged pharmaceutical product and method of manufacture for the purpose of illustrating the manner in which the invention may be used to advantage, it should be appreciated that the invention is not limited thereto. Accordingly, any and all modifications, variations, or equivalent arrangements which may occur to those skilled in the art, should be considered to be within the scope of the present invention as defined in the appended claims.