EP2155163A1

EP2155163A1 - Composition for injection including propofol and method of preparing the same

Info

Publication number: EP2155163A1
Application number: EP07833455A
Authority: EP
Inventors: Tae-Won Song; Se-Il Sohn; Ung-Kil Jee; Jin-Kyu Park; Tae-Sung Kim; Gu-Youn Kwon
Original assignee: Dae Won Pharmaceutical Co Ltd; Daewoong Pharmaceutical Co Ltd
Current assignee: DAE WON PHARMACEUTICAL CO., LTD.
Priority date: 2007-05-17
Filing date: 2007-10-19
Publication date: 2010-02-24
Also published as: KR20080102010A; WO2008143380A1; EP2155163A4

Abstract

A novel injectable composition containing propofol (2,6-diisopropylphenol) and a preparation method of the same are provided. The injectable propofol composition includes: propofol at a concentration of about 1-2% w/v, poloxamer 188 about at a concentration of 6-15% w/v, macrogol 15 hydroxystearate about at a concentration of 0.2-1% w/v, and edetate about at a con¬ centration of 0.0001-0.001% w/v.

Description

COMPOSITION FOR INJECTION INCLUDING PROPOFOL AND METHOD OF PREPARING THE

SAME

Technical Field

[1] The present invention relates to a novel composition for injection including propofol and a preparation method of the same. Background Art

[2] Propofol (2,6-disopropylphenol) is a short-acting and quickly metabolized general anesthesia. Its high rate of metabolization leaves almost no residue in the body, so it is useful not only for short term anesthesia but also for long term anesthesia. Moreover, propofol enables better control of the depth of anesthesia while a patient is under anesthesia, and patients in general recover quickly from the anesthetic state. When patients recover, they are in a fully conscious state and hardly experience any adverse drug reactions like nausea, emesis, and others.

[3] If an injectable propofol composition uses Cremophor EL as a surfactant, anaphylactoid reactions occur. In addition, if lipids such as soybean oil, egg lecithin, and others are used as the solubilizer of a microemulsion, a high dose of svch lipids for a long surgery may cause side effects including hyperlipidemia, thrombosis and so on. In addition, because lipids cause proliferation of microorganisms, extra caution is required in handling formulations thereof.

[4] In order to overcome shortcomings of the oil-in-water (OAV) emulsion, many researchers have tried to develop new propofol formulations by solubilizing propofol in the water phase with the aid of a hydrophilic surfactant. Especially, there is a need to develop an injectable composition which is safe even for high-dose administration, transparent (or diaphanous), pharmaceutically stable, and sterilizable under high pressure steam to inhibit the growth of microorganisms. Disclosure of Invention Technical Problem

[5] It is therefore an object of the present invention to provide an injectable propofol composition that is safe even for high-dose administration, retains transparency at all temperatures during a storage period, and is sterilizable under high pressure steam.

[6] Another object of the present invention is to provide a preparation method of the injectable composition described above.

[7] Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it should be obvious to those skilled in the art of the present invention that the objects and advantages of the present invention can be realized by the means as claimed and combinations thereof. Technical Solution

[8] In accordance with an aspect of the present invention, there is provided an injectable composition that comprises propofol at a concentration of about 1-2% w/v, poloxamer 188 at a concentration of about 6-15% w/v, macrogol about 15 hydroxystearate at a concentration of about 0.2-1% w/v, and edetate at a concentration of about 0.0001-0.001% w/v.

[9] In accordance with another aspect of the present invention, there is provided a preparation method of an injectable composition, which comprises: a) dissolving about 6-15% w/v poloxamer 188 in purified water; b) adding about 1-2% w/v propofol to the solution of step a) and stirring the mixture; c) adding macrogol 15 hydroxystearate and edetate to the mixture of step b) until the mixture contains about 0.2-1% w/v macrogol 15 hydroxystearate and about 0.0001-0.001% w/v edetate at room temperature; and d) adding a pH-control agent to adjust a pH value of the resulting solution of step c) to be roughly between 6.0 and 8.5.

Advantageous Effects

[10] An injectable propofol composition according to a preferred example of the present invention is safe even for high-dose administration, remains transparent during a storage period, and is thermodynamically stable, thereby being sterilizable under high pressure steam. Further, the inventive composition shows no change in transparency and particle size when it is mixed in aqueous solution or stored at high and low temperatures. Mode for the Invention

[11] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The aspects and features of the present invention and methods for achieving the aspects and features will be apparent by referring to the embodiments to be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed hereinafter, but can be implemented in diverse forms. The matters defined in the description, sirh as the detailed construction and elements, are nothing but specific details provided to assist those of ordinary skill in the art in a comprehensive understanding of the invention, and the present invention is only defined within the scope of the appended claims.

[12] In the following description of the present invention, terms used are for explaining embodiments of the present invention, but do not limit the scope of the present invention. In the description, a singular expression may include a plural expression unless specially described. The term "comprises" andhr "comprising" used in the description means that one or more other components, steps, operation and/όr existence or addition of devices are not excluded in addition to the described components, steps, operation and/όr devices.

[13] An injectable composition according to a preferred example of the present invention contains about 1-2% w/v propofol, about 1-6% w/v poloxamer 188, about 0.2-1% w/v marcrogol 15 hydroxy-stearate, about 0.0001-0.001% w/v edetate, glycerin, sodium ascorbate, and sodium hydroxide.

[14] A microemulsion is a kind of emulsifiable concentrate (or emulsion)that is transparent or diaphanous unlike regular emulsions. The microemulsion can be prepared as a thermodynamically stable formulation consisting of micro-particles not larger than 100 nm. An injectable composition according to one example of the present invention is a transparent microemulsion having a particle size not larger than 100 nm, and can undergo a sterile filtration as well as high pressure steam sterilization (described later). Because the microemulsion is transparent, it can be visually examined to detect any foreign matters therein. Also, the microemulsion formulations have become simplified and a possible risk of contamination from foreign matter can be prevented in advance.

[15] The injectable composition according to a preferred example of the present invention contains about 1-2% w/v propofol.

[16] Propofol (2,6-disopropylphenol) is used for induction and maintenance of general anesthesia, sedation of mechanically ventilated intensive care patients, and others. In general, 1.5-2.5 mg/kg propofol is used to induce general anesthesia, and propofol blood concentration for maintenance of clinical anesthesia ranges from 2-10 μg/ml with an actual dose of 4-12 mg/ hr/kg. The injectable composition according to a preferred example of the present invention is safe even under high-dose conditions like lL/day.

[17] An injectable propofol composition may be pharmaceutically unstable due to a reversible oxidative reaction. Even though propofol exists in the form of a colorless monomer, it can be converted through oxidation to form yellow propofol dimmer quinine (Free Radical and Drug Oxidation Products in an Intensive Care Unit Sedative: Propofol with Sulfite. Max T. Baker, Marc S. Gregerson, Sean M. Martin, Garry R. Buettner. Crit Care Med 2003, Vol. 31, No. 3, 787-792). This discoloration is reversible and sometimes oxurs corresponding to an energy state. In detail, propofol is colorless or transparent in a high energy state (i.e., catalyzed by light), but becomes yellowish in a low energy state (i.e., in the absence of light), which is reversible.

[18] The injectable composition according to a preferred embodiment of the present invention contains about 0.0001-0.001% w/v edentate to overcome the pharmaceutical instability caused by the reversible oxidative reaction of propofol. Edetate means Ethylenediamine Tetraacetic Add (EDTA) and its derivatives. For example, disodium derivative is known as edentate disodium. Edetate above a certain concentration demonstrates inhibition of microbial proliferation, but it does not show such effects within the concentration range used for the injectable composition according to a preferred example of the present invention. Although edetate is not involved in the inhibition of microbial proliferation for the injectable composition according to a preferred example of the present invention, it may be utilized to overcome the pharmaceutical instability of the composition caused by the reversible oxidation of propofol. In general, edetate, as a chelating agent, is capable of not only suppressing a reaction with a very small amount of metal ions through chelating in solution phase, but also removing free radicals in the solution to suppress oxidative reactions by ions. In short, about 0.0001-0.001% w/v, more specifically, about 0.0001-0.0008% w/v edetate can prevent yellowing of a propofol composition and serve to maintain a colorless, transparent propofol formulation.

[19] The injectable composition according to a preferred example of the present invention contains about 6-15% w/v poloxamer 188 as a surfactant. In general, poloxamers are non-(cyto)toxic polymer surfactants and poly(a-oxyethylene-b-oxypropylene-a-oxyethylene) triblock copolymers. They usually have good water solubility, but properties of individual poloxamer are substantially diverse. The pharmaceutical compatibility of various poloxamers are well established, and particularly poloxamer 407 and poloxamer 188 (P407 and Pl 88) were approved for parenteral administration. Among them, poloxamer 188 is used for intravenous injection and no adverse effect has been reported for the clinical use of propofol at a dose of 2960 mg/kgfor a day (Safety of Purified Poloxamer 188 in Sickle Cell Disease: Phase I Study of a Non-ionic Surfactant in the Management of Acute Chest Syncrome. Samir K. Ballas, Beatrice Files, Lori Lirhtman- Jones, Lennette Benjamin, Paul Swerdlow. Hemoglobin 2004, Vol. 28, No. 3, 85-102), again confirms the safety of clinical use of the high-dose injectable propofol composition. Suppose that an injectable propofol composition was used at a dose of 2960 mg/kg for a day. In this case, a clinically permitted concentration of poloxamer 188 can be about 15% w/v. Poloxamer is a block copolymer composed of hydrophilic polyoxyethylene and hydrophobic polyoxypropylene and forms micelles, in which the hydrophobic region is sealed inside while the hydrophilic (or water-soluble) region is hydrated by outside water.

[20] Preferably, the injectable composition according to a preferred example of the present invention contains poloxamer 188 at about 10-15% w/v concentration. Although propofol can be dissolved in poloxamer 188 at about 6% w/v concentration, a suitable concentration for poloxamer 188 is above about 10% w/v, 10.1% w/v for example, so that phase stability can be maintained even when poloxamer 188 is mixed with an aqueous solution or another injection formulation for clinical use. Poloxamer 188 at about 15% w/v concentration or less is safe for clinical use.

[21] The injectable composition according to a preferred embodiment of the present invention contains about 0.2-1% w/v, more specifically, about 0.7-1% w/v macrogol 15 hydroxystearate (Solutol HS 15T, BASF, Germany). Macrogol 15 is cytotoxic when used at high doses, but no adverse effect has been reported at low doses. Therefore, it is safe to use macrogol 15 as a supplementary solubilizer (LD50 rat, iv=1.2g/kg). In particular, phase stability of the injectable composition according to a preferred embodiment of the present invention is secured by containing about 0.2-1% w/v macrogol 15 hydroxyestearate. Meanwhile, an injectable composition containing about 0.1% macrogol 15 hydroxystearate can become turbid or opaque when it is diluted in an aqueous solution. If poloxamer 188 was the only solubilizer used, particles in the injectable composition may become larger at a low temperature and the composition can become turbid again. However, with use of macrogol 15 hydroxystearate as a supplementary solubilizer together with poloxamer 188, the injectable composition of the present invention becomes pharmaceutically stable at all temperatures. Meanwhile, if macrogol 15 hydroxystearate with greater than about 1% w/v concentration is used at high doses, stability of the composition can be problematic and the composition may become white-turbid during the high-pressure steam sterilization process. [22] The injectable composition according to a preferred embodiment of the present invention contains about 0.2-1% w/v macrogol 15 hydroxystearate and about 6-15% w/v poloxamer 188, and can be sterilizable under high-pressure steam conditions. Sterile filtration through sterile works or a sterile filter is exposed to high contamination during a preparation process, and the preparation process is not only difficult but also costly. As such, the high pressure steam sterilization is the next preferable option to prepare an aseptic composition for injection, provided that the composition is thermodynamically stable so as not to undergo any phase change through high pressure sterilization and become turbid again. As discussed earlier, the injectable composition according to a preferred embodiment of the present invention does not experience changes in particles or transparency even under high pressure sterilization conditions.

[23] The injectable composition according to a preferred embodiment of the present invention contains an anti-oxidant. Examples of the anti-oxidant include, but are not limited to, sodium ascorbate, ascorbic add, sulfite compounds, cystein, propylgallate, thiodipropionic add, monothioglycerol and others. In detail, if sodium ascrobate is used as an anti-oxidant, an oxidative reaction of propofol is suppressed so that the injectable composition can maintain the same phase before and after the high pressure steam sterilization. Sodium ascorbate may be used at a concentration of about 0.005-4.8% w/v, and more spedfically at a concentration of about 0.005-0.1%.

[24] Moreover, the injectable composition according to a preferred embodiment of the present invention may contain a pH-control agent such as sodium hydroxide if needed to be physiologically neutral with a pH typically between 6.0 and 8.5. Examples of the pH-control agent include, but are not limited to, sodium hydroxide, dtric add, acetic add, phosphoric add, gluconic add, ascorbic add, succinic add, and others.

[25] Also, the injectable composition according to a preferred embodiment of the present invention may contain a proper osmotic modifier to become isotonic with blood. Examples of the osmotic modifier include, but are not limited to, glycerin, trehalose, dextrose, solbitol, mannitol, and others.

[26] Since the injectable composition according to a preferred embodiment of the present invention does not experience physical changes in particle size, phase and so on in the presence of other drugs, it can be mixed with other aqueous solutions or drugs for clinical use. Further, it is very stable at all temperatures and there is hardly any change in particle size or phase due to temperature changes which may occur during distribution of propofol formulations. [27] In view of the above description and the examples below, one of ordinary skill in the art will be able to practice the invention as claimed without undue experimentation. The foregoing will be better understood with reference to the following examples that detail certain procedures for the preparation of formulations according to the present invention. All references made to these examples are for the purposes of illustration. The following examples should not be considered exhaustive, but merely illustrative of only a few of the many embodiments contemplated by the present invention.

[28] To prepare an injectable composition according to a preferred example of the present invention, about 6-15% w/v poloxamer 188 is first dissolved in purified water, and about 1-2% w/v propofol is added thereto and stirred together. Then, macrogol 15 hy- droxystearate and edetate are added to the mixture at room temperature to obtain macrogol 15 hydroxystearate with a concentration of about 0.2-1% w/v and edetate with a concentration of about 0.0001-0.001% w/v in the mixture. Next, a pH-control agent is added to control the pH of the composition to be roughly between 6.0 and 8.5.

[29] The injectable composition prepared by a preferred example of the present invention takes a transparent microemulsion form.

[30] In detail, about 6-15% w/v poloxamer 188 is dissolved in purified water, and about

1-2% w/v propofol is added thereto and stirred together at about 60-70⁰C. Then, macrogol 15 hydroxystearate and edetate are added to the mixture at room temperature to obtain macrogol 15 hydroxystearate at a concentration of about 0.2-1% w/v and edetate at a concentration of about 0.0001-0.001% w/v in the mixture. Macrogol 15 hydroxystearate and edetate are added at room temperature to prevent the occurrence of a white turbid phenomenon that is caused when macrogol 15 hydroxysterate is added at a high temperature. The resulting solution is filtered and sterilized under high pressure steam conditions after its pH is adjusted to about 8 with a pH-control agent. This is so because the high pressure steam sterilization process may lower the pH of the solution by approximately 1. In this manner, the final pH of the solution, having gone through the high pressure steam sterilization process, is adjusted to about 7. The injectable propofol composition of the present invention maintains its transparent phase even after the high pressure steam sterilization treatment.

[31] The preparation method of an injectable composition according to a preferred example of the present invention may further include adding an anti-oxidant, before adding a pH-control agent to adjust the solution to roughly between 6.0 and 8.5.

[32] The preparation method of an injectable composition according to a preferred example of the present invention may further include adding an osmotic modifier, before adding a pH-oontrol agent to adjust the solution to roughly between 6.0 and 8.5.

[33] In the preparation method of an injectable composition according to a preferred example of the present invention, poloxamer 188 is added at a concentraion of about 10-15% w/v.

[34] In the preparation method of an injectable composition according to a preferred example of the present invention, macrogol 15 hydroxystearate is added at a concentration of about 0.5-0.7% w/v.

[35] The present invention is more specifically explained by the following examples. It will be appreciated by any person skilled in this art that the present invention includes the following examples and can be variously modified and altered within the technical concept of the present invention.

[36] EXAMPLE 1 [37] An injectable composition containing lOmg propofol per ImI of an injectable propofol microemulsion has the following composition shown in Table 1 (100 ml in total prepared)

[38] Table 1 [Table 1] [Table ]

[39] With the ingredients listed above, an injectable propofol microemulsion is prepared as follows. Every step of the preparation process takes place under nitrogen purging and the weight of each one of the ingredients is a weight in a final volume. 1Og of Poloxamer 188 was dissolved in 80 ml of distilled water, and Ig of propofol was added thereto at about 60-7ObC and stirred together for about 2 hours. The mixture containing propofol was then left aside at room temperature. Later, the mixture was added with 0.7g of macrogol 15 hydroxystearate, followed by Ig of glycerin, O.Olg of sodium ascorbate, and 0.0008g of disodium edetate. The pH of the resulting composition was adjusted to 8 by sodium hydroxide. After the pH adjustment, a nitrogen fill was performed, followed by a filtration step at about 121⁰C for about 20 minutes with the aid of a high-pressure sterilizer (SH-29A, Human sciences). Lastly, the pH of the resolution solution was adjusted to a final pH of about 7.

[40] EXAMPLE 2 [41] The same procedure as Example 1 was carried out to obtain an injectable propofol formulation having essentially the same composition as Example 1, except that poloxamer 188 content was about 15% w/v (refer to Table 2).

[42] Table 2 [Table 2] [Table ]

[43] EXAMPLE 3 [44] The same procedure as Example 1 was carried out to obtain an injectable propofol formulation having essentially the same composition as Example 1, except that macrogol 15 hydroxystearate content was about 0.5% w/v (refer to Table 3).

[45] Table 3 [Table 3] [Table ]

[46] EXAMPLE 4 [47] The same procedure as Example 1 was carried out to obtain an injectable propofol formulation having essentially the same composition as Example 1, except that macrogol 15 hydroxystearate content wsa about 0.2% w/v (refer to Table 4).

[48] Table 4 [Table 4] [Table ]

[49] EXAMPLE 5 [50] The same procedure as Example 1 was carried out to obtain an injectable propofol formulation having essentially the same composition as Example 1, except that macrogol 15 hydroxystearate content was about 1% w/v (refer to Table 5).

[51] Table 5 [Table 5] [Table ]

[52] EXAMPLE 6 [53] The same procedure as Example 1 was carried out to obtain an injectable propofol formulation having essentially the same composition as Example 1, except that disodium edetate content is about 0.0001% w/v (refer to Table 6).

[54] Table 6

[Table 6] [Table ]

[55] EXAMPLE 7 [56] The same procedure as Example 1 was carried out to obtain an injectable propofol formulation having essentially the same composition as Example 1, except that the disodium edetate content was about 0.001% w/v (refer to Table 7).

[57] Table 7 [Table 7] [Table ]

[58] EXAMPLE 8 [59] The same procedure as Example 1 was carried out to obtain an injectable propofol formulation having essentially the same composition as Example 1, except that the disodium edetate content was about 0.005% w/v (refer to Table 8).

[60] Table 8 [Table 8] [Table ]

[61] COMPARATIVE EXAMPLE 1 [62] An injectable propofol microemulsion having the composition listed in Table 9 was prepared using poloxamer 407 and poloxamer 188 in a ratio of 7:3 (Example 7 disclosed in WO 2001/64187).

[63] Table 9 [Table 9] [Table ]

[64] COMPARATIVE EXAMPLE 2 [65] An injectable propofol microemulsion having the composition listed in Table 10 was prepared (Example 1 disclosed in KR Pub. No. 2001-0039671).

[66] Table 10 [Table 10] [Table ]

[67] COMPARATIVE EXAMPLE 3 [68] An injectable propofol microemulsion having the composition listed in Table 11 was prepared.

[69] Table 11 [Table 11] [Table ]

[70] COMPARATIVE EXAMPLE 4 [71] An injectable propofol microemulsion having the composition listed in Table 12 was prepared. [72] Table 12 [Table 12] [Table ]

[73] With the composition listed above, a propofol formulation was prepared as follows. 6g of poloxamer 188 was dissolved in 80 ml of purified water, and Ig of propofol was added thereto. The mixture was stirred until the resulting solution became transparent. Afterwards, glycerin was pipetted to a desired scale mark, and the pH of the resulting microemulsion was adjusted to 8 by sodium hydroxide. After the pH adjustment, a nitrogen fill was performed, followed by a filtration step at 121⁰C for about 20 minutes with the aid of a high-pressure sterilizer (SH-29A, Human sciences). Lastly, the pH of the resolution solution was adjusted to a final pH of about 7.

[74] COMPARATIVE EXAMPLE 5 [75] An injectable propofol formulation containing about 10% w/v poloxamer 188 and having the composition listed in Table 13 was prepared by using the same composition and process described in Comparative Example 4.

[76] Table 13 [Table 13] [Table ]

[77] COMPARATIVE EXAMPLE 6 [78] An injectable propofol formulation was prepared by using the same composition, except for disodium edetate, and the same process described in Example 1.

[79] Table 14 [Table 14] [Table ]

[80] COMPARATIVE EXAMPLE 7 [81] An injectable propofol formulation containing about 0.1% w/v macrogol 15 hydrox- ystearate and having the composition listed in Table 15 was prepared by using the same composition and process described in Example 1.

[82] Table 15

[Table 15] [Table ]

[83] The following experiments are for illustrative purposes only, and it should be understood that the scope of the present invention is not limited by the examples in any manner.

[84] EXPERIMENT 1: Observation of phase change in examples and comparative examples after high pressure steam sterilization treatment

[85] Each one of the examples and comparative examples was sterilized at 121⁰C for 20 minutes under high-pressure steam conditions. Each example was observed before and after the sterilization treatment for phase changes. In addition, optical transmittance of each example was measured by employing a UV/VIS spectrophotometer(V550, Jasco) at a wavelength of 600 nm. These observation results are provided in Table 16 below.

[86] Table 16

[Table 16] [Table ]

[87] As can be seen from Table 16, although Examples 1-8 showed no change in their phase and transparency before and after high pressure steam sterilization treatment, but some phase changes were observed in the Comparitive Examples. For instance, Comparitive Examples 1-5 were colorless and transparent at the time of formulation, but were subjected to oxidative reactions and became yellowish after the high pressure steam sterilization treatment. Meanwhile, examples containing sodium ascorbate remain colorless even after the high pressure steam sterilization treatment. In addition, Comparitive Example 3 having a high content of macrogol 15 hydroxystearate became turbid or opaque after the high pressure steam sterilization treatment and its phase became unstable. Example 5 containing about 1% w/v macrogol 15 hydroxystearate kept its transparency throughout the high pressure steam sterilization treatment, but it became white-turbid when the content of macrogol 15 hydroxystearate was increased above 1% w/v. [88] EXPERIMENT 2: Stability test [89] After the Examples and Comparitive Examples were sterilized at 121⁰C for 20 minutes under high pressure steam conditions, they were left aside for 1 month at a relative humidity of 75% and at room temperature and 4O⁰C, respectively, and for 1 day in the absence of light. Using the same method as Experiment 1, the optical transmittance of each of the examples was measured.

[90] Table 17 [Table 17] [Table ]

[91] As can be seen from Table 17, both Examples and Comparitive Examples stably remained colorless after the lapse of 1 month at room temperature. However, after they were stored in a dark place for 1 day, all of the Comparitive Examples containing no edetate became yellowish yet turned to colorless again after they were irradiated with light. In addition, all of the Comparitive Examples except for Comparitive Example 7 became yellowish after the lapse of 1 month under conditions of a temperature of 4O⁰C and 75% relative humidity. Also, it was confirmed that edetate at about 0.0001% w/v concentration or above could prevent discoloration caused by reversible oxidative reactions, thereby permitting the resulting formulations to be pharmaceutically stable. This is primarily because edetate, as a chelating agent, is capable of not only suppressing a reaction with a very small amount of metal ions through chelating in solution phase, but also removing free radicals in the solution to suppress oxidative reactions by ions.

[92] EXPERIMENT 3: Dilution test in aqueous solution

[93] In clinical use, a propofol anesthetic agent is usually mixed in another aqueous solution. Therefore, it is essential that the propofol anesthetic agent does not §p though any phase change in the presence of an aqueous solution. For the dilution test, Examples and Comparitive Examples were diluted in 0.9% physiological saline, 5% glucose solution, and Hartmann's solution at various concentrations, and optical transmittance of each one of the examples was measured by applying the same method as Experiment 1. Table 18 below shows observation results when the examples were diluted to 1/10 concentration in each one of the aqueous solutions.

[94] Table 18

[Table 18] [Table ]

[95] As can be seen from Table 18, all of the Examples and the Comparitive Examples 1,

2, 3 and 6 maintained phase stability and transparency despite the dilution in an aqueous solution. However, the optical transmittances of Comparitive Examples 4 and 5 show that the use of poloxamer 188 only was not enough to prevent a turbid phenomenon in the diluted propofol solutions over time. Meanwhile, in the case of Example No. 6 and the Comparative Example No. 6, each containing macrogpl 15 hy- droxystearate as a supplementary surfactant, no physical changes were observed in particle size, phase, and others, of the resulting formulations even when they were administered in mixed form. Moreover, unlike the Example No.4 containing 0.2% w/v macrogpl 15 hydroxystearate, Comparative Example No.7 containing 0.1% w/v macrogol 15 hydroxystearate lost its transparency when it was diluted in an aqueous solution and became turbid.

[96] EXPERIMENT 4: Phase changes under different storage conditions

[97] Propofol formulations are sometimes exposed to high or low temperature environments during distribution or storage. Thus, phase changes of the propofol formulations under high temperature storage condition(e.g., 6O⁰C) or high temperature storage condition(e.g., 4⁰C) were observed, and optical transmittance of each of the examples was also measured by applying the same method as EXPERIMENT 1. These observation results are provided in Table 19 below. [98] Table 19

[Table 19] [Table ]

[99] As is evident from Table 19, all of the Examples and Comparative Example No. 7 did not show any changes in transparency and phase at high or low temperatures. However, all of the Comparitive Examples containing no edetate turned yellowish. In particular, optical transparency of Comparative Example No. 3 was decreased as it became slightly turbid or opaque at high or low temperatures. Moreover, at low temperature storage conditions, Comparative Example No. 4 had an unstable phase and its optical transmittance was decreased, while Comparative Example No. 5 containing 10% w/v poloxamer 188 remained transparent throughout. [100] EXPERIMENT 5: Influence of edetate concentration on injectable propofol compositions

[101] The relationship between inhibition effects of microbial proliferation and different concentrations of edetate contained in an injectable composition according to a preferred embodiment of the present invention was examined. The test was conducted using of Escherichia coli, Pseudomonas aeruginosa and Candida albicans as test microorganisms. In a preferred example, propofol was dissolved in a water immiscible solvent, emulsified with water, and stabilized by a surfactant to prepare a mi- croemulsion. Additionally, Escherichia coli, Pseudomonas aeruginosa and Candida albicans were incubated respectively in 1 ml of a water-cleansed suspension at a temperature in the range of 20-25⁰C. After 24 hour-, 48 hour-, and 7 day- incubation, the number of surviving microorganisms in each incubator (or culture plate) was counted.

[102] Test formulations were prepared by the same process but with varying concentrations of edetate, i.e., 0 %(CO. EX. 6), 0.0008% (EX.l), 0.001% (EX. 5), and 0.005% (EX. 6). Test results are shown in Table 20 below.

[103] Table 20

[Table 20] [Table ]

[104] As can be seen from Table 20, growth of microorganisms was inhibited in for- mulations containing 0.005% w/v edetate as in Diprivan or Example No. 8. However, this effect was not observed in formulations containing 0.001% w/v edetate. Therefore, one can conclude that propofol formulations of the present invention do not affect the growth of microorganisms as long as edetate was used within a range for securing pharmaceutical safety of the formulations.

Claims

[I] An injectable composition comprising: propofol at a concentration of about 1-2% w/v, poloxamer 188 at a concentration of about 6-15% w/v, macrogol 15 hydroxystearate at a concentration of about 0.2-1% w/v, and edetate at a concentration of about 0.0001-0.001% w/v.

[2] The injectable composition of claim 1 is a transparent microemulsion.

[3] The injectable composition of claim 2, wherein the transparent microemulsion retains transparency even after a high pressure steam sterilization treatment. [4] The injectable composition of claim 1, wherein the edetate is a pharmaceutical stabilizing substance capable of preventing yellowing of the composition. [5] The injectable composition of claim 1, further comprising an anti-oxidant.

[6] The injectable composition of claim 5, wherein the anti-oxidant is sodium ascorbate. [7] The injectable composition of claim 1, wherein the concentration of poloxamer

188 is about 10-15% w/v. [8] The injectable composition of claim 1, wherein the concentration of macrogol 15 hydroxystearate is about 0.5-0.7% w/v. [9] The injectable composition of claim 1, further comprising an osmotic modifier or a pH-control agent. [10] The injectable composition of claim 9, wherein the osmotic modifier is glycerin and the pH-control agent is sodium hydroxide.

[I I] A preparation method of an injectable composition, comprising: a) dissolving about 6-15% w/v poloxamer 188 in purified water; b) adding about 1-2% w/v propofol to the solution of step a) and stirring the mixture; c) adding macrogol 15 hydroxystearate and edetate to the mixture of step b) until the mixture contains about 0.2-1% w/v macrogol 15 hydroxystearate and about 0.0001-0.001% w/v edetate at room temperature; and d) adding a pH-control agent to adjust a pH value of the resulting solution of step c) to be roughly between 6.0 and 8.5.

[12] The method of claim 11, wherein the injectable composition is a transparent microemulsion. [13] The method of claim 11, wherein propofol is added at a temperature in the range of about 60-70⁰C. [14] The method of claim 11 , further comprising: e) after step d) of adjusting a pH value of the injectable composition with the pH- control agent to about 8, filtering the solution and sterilizing the filtered solution with high pressure steam. [15] The method of claim 14, wherein the pH value of the solution after the high pressure steam sterilization treatment is adjusted to about 7, and the solution is transparent. [16] The method of claim 11, wherein the edetate is a pharmaceutically stable substance capable of preventing yellowing of the composition. [17] The method of claim 11 , further comprising: cl) adding an anti-oxidant prior to step d) for adjusting the pH value to be roughly between 6.0 and 8.5 [18] The method of claim 11 , further comprising: c2) adding an osmotic modifier prior to step d) for adjusting the pH value to be roughly between 6.0 and 8.5 [19] The method of claim 11, wherein the concentration of the poloxamer 188 is about 10-15% w/v. [20] The method of claim 11, wherein the concentration of the macrogol 15 hydrox- ystearate is about 0.5-0.7% w/v.