Abstract:
The present invention is directed to a sterile pharmaceutical composition comprising a propofol containing oil-in-water emulsion formulation having as an antimicrobial agent, a member selected from the group consisting of benzyl alcohol and ethylene diamine tetra acetic acid; benzethonium chloride; and benzyl alcohol and sodium benzoate.

Description:
FIELD OF THE INVENTION 
     The present Invention relates to pharmaceutical compositions containing 2,6-diisopropylphenol. 
     BACKGROUND OF THE INVENTION 
     Propofol (26-diisopropylphenol) an injectable anesthetic which has hypnotic properties and can be used to induce and maintain general anesthesia and for sedation. Injectable anesthetics such as propofol are administered directly into the bloodstream. This results in a rapid onset of anesthesia influenced almost entirely by the rate at which the anesthetic agent crosses the blood-brain barrier. Therefore, the anesthetic agent must have sufficient lipid solubility to be able to cross this barrier and depress the relevant mechanisms of the brain. Propofol is poorly water soluble and therefore is generally formulated as an emulsion. Propofol containing emulsions have been shown to support microbial growth. Therefore it is desirable to formulate propofol emulsions in a manner in which microbial growth is prevented. EDTA (ethylene diamine tetraacetic acid) has been shown to delay, but not prevent, the onset of microbial growth in propofol emulsions. See U.S. Pat. No. 5,714,520. 
     Accordingly it is an object of the present invention to provide a propofol containing pharmaceutical composition that provides antimicrobial benefits above that found in existing compositions and/or prevents the onset of microbial growth in such compositions. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a sterile pharmaceutical composition comprising a propofol containing oil-in-water emulsion formulation having as an antimicrobial agent, a member selected from the group consisting of benzyl alcohol and ethylene diamine tetraacetic acid; benzethonium chloride; and benzyl alcohol and sodium benzoate. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The term &#34;anti-microbial&#34; means an agent which delays onset or retards rate of growth to less than 1 logarithmic increase over a 24 hour period as compared to an unpreserved formulation. 
     The composition of the present invention comprises an oil in water emulsion in which the 2,6-diisopropylphenol, either alone or dissolved in a water immiscible solvent, for example a vegetable oil, is emulsified with water by means of surfactant. 
     Typically the solvent is an oil such as soy bean oil, safflower oil, cottonseed oil, corn oil, sunflower oil, arachis oil, castor oil, or olive oil. Preferably the oil is soybean oil. Alternatively the solvent can be an ester of a medium or long chain fatty acid, for example a mono-,di-, or triglyceride; or a compound such as ethyl oleate, isopropyl myristate, isopropyl palmirate, a glycerol ester or a polyoxyl hydrogenated castor oil. Other suitable solvents may be marine oils, for example cod liver or other fish derived oils, or fractionated oils, such as fractionated coconut oil or modified soybean oil. The composition of present invention may also comprise a mixture of two or more of the above water immiscible solvents. 
     The 2,6-diisopropylphenol, either alone or dissolved in the water immiscible solvent, is emulsified with the aid of a surfactant. Suitable surfactants include synthetic non-ionic surfactants, for example ethoxylated ethers and esters and polypropylene polyethylene block copolymers, and phosphatides, as for example egg and soy phosphatides. Preferably, the surfactant is egg phosphatide. 
     Preferred compositions of the present invention comprise from 0.1 to 5.0% by weight, preferably 1 to 2% by weight, and most preferably 2% by weight of 2,6-diisopropylphenol; from to 2 to 30% by weight, preferably 10 to 20% by weight of a nonionic surfactant; from 2 to 90% by weight of a water immiscible solvent, and the balance of the composition being water. 
     The antimicrobial systems utilized in the compositions of the present invention are selected from the group consisting of benzyl alcohol and ethylene diamine tetraacetic acid; benzethonium chloride; and bcnzyl alcohol and sodium benzoate. The concentration of the antimicrobial agents in the final composition will vary depending on the particular agent or agents selected. For instance in a preferred composition of the invention the amount of benzyl alcohol is in the range of about 0.0175% to 0.9% (w/v), more preferably about 0.07% to about 0.45%, most preferred in the range of 0.15%. In an alternate preferred composition of the invention, the amount of benzyl alcohol is about 0.07% to about 0.9%, optionally including an amount of EDTA of about 0.005%. Yet another embodiment provides a composition including an amount of benzethonium chloride of about 0.1% to about 0.1%. Optionally, the composition of the present invention include 0.07% nb. The most preferred compositions of the present invention include bcnzyl alcohol and nb. The compositions of the present invention may be prepared by conventional processes as for example that disclosed in U.S. Pat. No. 5,714,520. 
     The compositions of the present invention can also contain pH adjusting agents such as sodium hydroxide so they can be formulated at a physiologically neutral pH. 
     The compositions of the present invention may also be made isotonic by the incorporation of a suitable additive such as glycerol. 
     A particularly preferred composition of the present invention is as set forth below. 
     
                       TABLE 1______________________________________(weight percent)          Broad      Preferred                            Particularly Preferred  Component              Range          Range         Amount______________________________________2,6-       0.1-5.0    1.0-2.0  1.0  diisopropylphenol  Soybean Oil             1-30        10-30       10  Egg Phosphatide        0.2-2.0     0.7-2.0    1.2  Benzyl alcohol         0.0175-0.9    0.07-0.45  0.15  nb                     0.07           0.07          0.07  Glycerol                                            2.25  Sodium Hydroxide       q.s.           q.s.          q.s.  Water for Injection    to 100         to 100        to 100______________________________________ 
    
     The compositions of the present invention may be used for the induction of anesthesia prior to maintenance with a conventional inhalation anesthetic or they may used as a sole anesthetic agent for short duration or by repeated administration or by continuous infusion they may be use as a sole anesthetic agent of longer duration. 
     The invention is illustrated by the following representative examples: 
    
    
     EXAMPLE 1 
     The compositions of the present invention may be formulated following procedures well known to those skilled in the art. Specific reference is made to U.S. Pat. No. 5,714,520 which is hereby incorporated by reference. 
     EXAMPLE 2 
     Solutions of 0.45% benzyl alcohol/0.005% EDTA, 0.035%benzyl alcohol/0.005% EDTA, 0.45% benzyl alcohol/0.07%nb, and 0.35% benzyl alcohol/0.07%nb were passed through a 0.45 micron filter and tested by the USP 23 preservative effectiveness test as described in United States Pharmacopoeia 23-NF 18, 1995 Ed., Chapter 51, which is incorporated herein by reference. Briefly, this involves inoculating the test solution with 10 5  to 10 6  test organisms per milliliter and then determining the number of surviving organisms after 7, 14, 21, and 28 days incubation at 20-25° C. using standard microbiological methods. Day 0 data is not required by USP 23 but was included in this study. A filtration and was method was used to remove the inactivating agents for purposes of recovering the microorganisms, but other equivalent methods can also be validated for use. The USP test organisms include the bacteria Staphylococcus aureus, Escherichia coli, and Pseudomonoas aeruginosa, a yeast (Candida albicans), and a mold (Aspergillus niger). In order to meet the criteria of the USP 23 preservative effectiveness test, the bacteria must demonstrate a 90% (1 logarithmic) reduction at Day 7 and a 99.9% reduction (3 logarithmic) reduction at Day 14 from the initial inoculum level. The initial inoculum level can either be calculated knowing the stock culture concentration or by using a buffer control instead of the test solution. The results, using formulations which are 10% fat emulsions, are given below in Tables 2 through 5 where the number reported in the number of organisms pre milliliter. ND means not detected, i.e., below the levels of detection by the assay. 
     
                       TABLE 2______________________________________(0.45% benzyl alcohol/0.005% EDTA)  OrganismTime   A. niger          C. albicans                    E. coli                          P. aeruginosa                                   S. aureus______________________________________Inoculum  390,000 440,000   750,000                          460,000  610,000  per ml  product  0 Hr.       300,000    300          &lt;10     &lt;10          &lt;10                                 ND         ND              ND                                    Day 7       210,000    340,000                                      680        3,000                                   47,000  Day 14      210,000    350,000      190        200             7,200                                    Day 21      3,400      270,000                                      40         60                                   4,300  Day 28      130        105,000      10         10              1,020______________________________________ 
    
     
                       TABLE 3______________________________________(0.035% BENZYL ALCOHOL/0.005 EDTA)  OrganismTime   A. niger          C. albicans                    E. coli                          P. aeruginosa                                   S. aureus______________________________________Inoculum  390,000 440,000   750,000                          460,000  610,000  per ml  product  0 Hr.      300,000     310,000      360,000    310,000         430,000                                    Day 7      300,000     330,000                                      40         105,000                                   36,000  Day 14     210,000     310,000      &lt;10     68,000          3,500                                      ND  Day 21     120,000     320,000      &lt;10     67,000          740                                      ND  Day 28     29,000      110,000      &gt;10     38,000          170                                      ND______________________________________ 
    
     
                       TABLE 4______________________________________(0.45 benzyl alcohol/0.07 nb)  OrganismTime   A. niger          C. albicans                    E. coli                          P. aeruginosa                                   S. aureus______________________________________Inoculum  390,000 440,000   750,000                          460,000  610,000  per ml  product  0 Hr.       260,000    340,000       380,000   440,000         390,000                                    Day 7       260,000    390,000                                       86,000    101,000                                   30,000  Day 14      29,000     350,000       62,000    14,900          1,350                                    Day 2l      22,000     203,000                                       80,000    2,800           100  Day 28      290        87,000        76,000    150             10______________________________________ 
    
     
                       TABLE 5______________________________________(0.035 BA/0.07% NB) OrganismTime  A. niger         C. albicans                   E. coli                          P. aeruginosa                                   S. aureus______________________________________In-   390,000 440,000   750,000                          460,000  610,000  oculum  per ml  product  0 Hr.       370,000    450,000       420,000   550,000         520,000                                    Day 7       250,000    530,000                                       8,800,000 3,500,000                                   310,000  Day 14      130,000    410,000       7,100,000 3,400,000       92,000                                    Day 21      41,000     440,000                                       5,800,000 30,000                                   49,000  Day 28      13,000     300,000       2,180,000 7,000           22,100______________________________________ 
    
     EXAMPLE 3 
     The antimicrobial properties of various Propofol formulations were determined by a spiked hold time study. Briefly, a Propofol formulation is inoculated to achieve approximately 100 organisms per 10 mL sample. The organisms used include Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, Bacillus subtilis, Aspergillus niger, and Clostridium sporogenes. The inoculated samples are held for various times and then filtered in duplicate. The filters are washed with buffer and then placed on appropriate agar growth media. The antimicrobial agents should reduce the growth rate such that there is less than a 1 logarithm increase within a 24 hour period. 
     C. albicans presented the most resistance to the preservative system. The C. albicans results from the spiked hold time study are shown below for various propofol formulations. E. coli, P. aeruginosa, and B. subtilis also demonstrated some resistance to the antimicrobial agents (data not shown). The remaining test organisms increased less than 2-fold over the 7 day test period. The results are shown in cfu/mL. A value of &gt;300indicates too numerous to count; these data points may still meet the acceptance criteria of less than 1 logaritmic increase. In the Tables, BA=Benzyl Alcohol, NB=Sodium Benzoate. The percent of benzyl alcohol is indicated in w/v for each formulation. The percents Sodium benzoate, when present, is 0.07% (w/v). 
     
         ______________________________________Formulation     0 hours 1 24 hours  48 hours 1                                 7 days 1______________________________________0.45 BA/NB     37        35        28      56  0.15 BA only      59           102          &gt;300     &gt;300  0.15 BA/NB        59           45           &gt;300     &gt;300  0.13 BA/NB        66           57           &gt;300     &gt;300  0.10 BA/NB        53           59           &gt;300     &gt;300  0.07 BA/NB        34           120          &gt;300     &gt;300  0.035 BA/NB       33           125          &gt;300     &gt;300  0.0175 BA/NB      38           185          &gt;300     &gt;300______________________________________