HRP920429A2 - Oil-water emulsion of an x-ray contrasting substance - Google Patents

Description

The invention relates to an oil-water emulsion of an x-ray contrast agent based on an iodinated ester of fatty acids, which can be administered via injections and can be sterilized by heat, and which in the appropriate concentration, possibly after appropriate dilution, can be used in x-ray diagnostics, e.g. in lymphography.

Until now, various X-ray contrast emulsions have been proposed, especially those based on iodinated fatty acid esters, and were recommended for use in X-ray diagnostics, when it was determined that they are suitable for injection, especially intravenously. Certainly, the known existing emulsions do not meet all requirements to a sufficient or desired extent because, for example, they often do not have a sufficiently high ability to absorb X-rays. A particular problem in the application of these emulsions is their low stability, with the disadvantageous consequence that they cannot, or can be difficult to sterilize and cannot be stored long enough, for this reason, efforts have been made to improve the emulsions of X-ray contrast agents, especially with regard to their stability and clinical usability.

Thus, DE-PS 26 02 907 describes aqueous emulsions of iodinated glycerine ester of fatty acids with a content of 50 to 60% by weight of one glycerine ester of fatty acids with an alkyl chain length of fatty acids of at least 10 carbon atoms, 2 to 10% by weight of polyoxyethylene-sorbitol fatty acid ester as an emulsifier, with the remainder being twice distilled water, whereby the resulting emulsion can only be sterilized with T rays due to its instability at elevated temperatures.

M.Vermess et al described in J.Comput. Assist. Tomogr. 3 (1979), p. 25 to 31, fat emulsions containing iodine in various formulations. The best-known emulsion EDE 13 contained 53% by weight of iodinated ester of fatty acids of poppy oil (trade name Ethiodol), 10% alcohol, 0.45% soy lecithin and one phosphate buffer to adjust the pH value to 7. About 55% of the oil was in the eye particles with a diameter of 1 to 3 μm. According to the author's point of view, the size of the particles in the emulsion should be within the limits of 2 to 4 μ, if this emulsion is to maintain a sufficiently high power to absorb X-rays in the liver. As J.Reinick et al. found in Radiology 162 (1987), p. 43-47, the EDE 13 emulsion is still not stable and can only be produced in larger quantities with difficulty. In addition, this emulsion causes unwanted side effects, such as fever, so patients must be prepared with steroids.

From the American patent US-PS 4 404 182 it is known the production of an emulsion of iodinated ethyl ester of fatty acids of poppy oil (trade name Ethiodol) with licithin as an emulsifier, in which the emulsion is made in such a way that 30-35% by volume of fat particles have a radius of 2 up to 3 μm. The emulsion is sterilized by filtering through a membrane filter, because the emulsion is not heat stable, so sterilization in autoclaves is possible.

Finally, EP-A-0294534 describes an emulsion containing iodine, which would be used as an X-ray contrast agent. Starting from one or more iodinated lipids, eg iodinated fatty acid esters of poppy seed oil, cottonseed oil, soybean oil, etc. which are emulsified in one aqueous phase with emulsifiers, this emulsion is characterized by a content of 0.1 to 5% by weight of one or more amino acids, fatty acids and their salts and/or fat-soluble vitamins and/or carbamide, as well as one or more pharmacologically acceptable oils or fats, whereby these additives should contribute to improving the stability of the emulsion. Furthermore, the emulsion should contain iodized lipids in the amount of 2.5 to 65% by weight of particles with a diameter smaller than 0.5 μ. The described emulsions are so stable that they can be sterilized in an autoclave.

In the following, the existing state of the art will be considered with special reference to a number of publications published in EP-A-0294534.

From the stated state of the art, it follows that, on the one hand, emulsions, where a significant part of the dispersed phase has a particle size in the range of 2 to 4 μ, absorb X-rays much better, for example in the liver and spleen, so their task as an X-ray contrast agent is better filled than with corresponding emulsions with much smaller particle sizes, for example below 0.5 μm, which is claimed by E.Gimes et al. in Journal of Pharmaceutical Science 68 (1979), p. 52 to 56. On the other hand, it follows from EP-A-0294534 p. 4, line 45-47 that obtaining an emulsion of an X-ray contrast agent that can be sterilized by heat must have a particle size of dispersed iodinated ester of fatty acids smaller than 0.5 μm.

On the basis of this state of the art, it was apparently not possible to realize emulsions of X-ray contrast agent that would combine the advantages of a very stable emulsion, meaning capable of being sterilized in autoclaves at 121°C with the advantages of one that absorbs X-rays well, so there has long been a large the need for a satisfactory solution to this problem.

Therefore, the presented invention has the task of obtaining an improved emulsion of X-ray contrast agent, which will be well tolerated by patients and have a good ability to absorb X-rays, as well as extraordinary stability, so that the emulsion will have good stability during storage and can be used at temperatures from 120 to 121°C for a long enough time to sterilize in autoclaves.

This task, according to the invention, is solved with an oil-water emulsion of an X-ray contrast agent, which can be sterilized by heat and applied by injections, and which has an internal phase of one or more organic iodinated compounds soluble in oil, especially iodinated esters of fatty acids, possibly with one or more highly refined glyceride oils, with one or more emulsifiers as well as, possibly, a co-emulsifier, and an external phase of distilled water with additives for isotonization, which is characterized by the fact that it contains one physiologically tolerable sodium lye buffer and one or more suitable inorganic and/or organic phosphates.

Unexpectedly, it was found that the oil-water emulsion according to the invention acquires, after adding a small but certain amount of the proposed physiologically tolerable buffer system, extraordinary stability, so that it can be sterilized in an autoclave at 12°C for about 15 to 20 minutes, and that after the sterilization process, with a suitable choice of the ratio of phosphate buffer and caustic soda and the total amount of buffer, a suitable average particle size can be achieved, and that this does not significantly affect the structure of the emulsion, and that this, filled into containers in a nitrogen atmosphere, has an extraordinary stability at storage, which greatly facilitates the safe handling of this X-ray contrast agent emulsion when administered by injection. At the same time, the X-ray contrast agent emulsion has a very good ability to absorb X-rays, so it can be successfully used for X-ray diagnostics.

As an X-ray contrast agent containing iodine, in the oil-water emulsion according to the invention, well-known commercially available organic compounds of iodine can be used, which can be applied by means of injections, and which are soluble in oils, and which give sufficiently strong positives in the X-ray imaging of organs contrasts. It is also convenient to use the iodinated ester of fatty acids, especially the glycerides of fatty acids, above all the triglycerides of fatty acids, such as, for example, the ethyl ester of fatty acids of iodized poppy oil, which is purchased under the trade name Lipiodol UF, then iodized soybean oil, cottonseed oil, peanut oil, iodized fish oil, etc. Iodized fatty acid esters are usually used in an amount of 5 to 40% by weight compared to the finished emulsion.

The emulsion according to the invention may possibly contain one or more iodized, highly refined, glyceride oils, which can be used for injecting food, such as soybean oil, safflower oil, medium-long chain triglycerides, etc. By adding them, the density of the oil droplets as the internal phase in the emulsion can be reduced and thereby prevent sedimentation.

The emulsion according to the invention contains one or more emulsifiers, which must have the necessary purity for this type of injection application. Such emulsifiers are known and can be obtained commercially. For the purposes of this invention, naturally obtained emulsifiers are suitable, especially lecithins, for example from soy, and especially lecithin from eggs. At the same time, suitable ratios of phospholipid fractions contained in lecithins can be adjusted by known special refining and fractionation procedures. The use of egg lecithin with a phosphatidylcholine content > 75% and a kephalin content < 15% is particularly suitable. It is possible to replace it with fractions of soy lecithin of high purity.

Furthermore, the emulsions according to the invention can contain suitable co-emulsifiers, whereby alkaline salts of fatty acids with long chains, such as, for example, palmitic acid, oleic acid or stearic acid, are particularly suitable.

The amounts of lecithin are generally in the range of 0.4 to 35 g/l of the finished emulsion according to the invention, while the amounts of co-emulsifiers, eg alkaline salts of fatty acids, are generally in the range of 0.2 to 1 g/l of the finished emulsion.

The external phase of the emulsion according to the invention contains distilled water, i.e. highly purified water of injection quality (aqua ad injectabilia) as well as isotonization additives, with which the external phase of the emulsion according to the invention is isotonically adjusted to human blood. As additives for isotonization, physiologically tolerable polyols, such as glycerin, sorbitol or xylitol, are particularly suitable. It is especially convenient to use glycerin. Additives for isotonization are added to the emulsion in the quantities necessary for isotonization, eg in the case of glycerin, 25 g/l compared to the finished emulsion.

The extraordinary heat and storage stability of the emulsion will be achieved according to the invention by adding a physiologically tolerable sodium hydroxide buffer in an appropriate concentration, eg 1 n sodium hydroxide, and one or more suitable inorganic and/or organic phosphates. The emulsion according to the invention contains disodium hydrogen phosphate as an inorganic phosphate. As organic phosphates, especially physiologically tolerable organic phosphoric acid esters come into consideration, which can be exposed to the heat sterilization process at 121°C for 15 to 20 minutes without significant degradation. Here, good results have been achieved especially with glycerophosphates, which until now have been used in commercially available infusion solutions, which are introduced through veins. They usually represent a mixture of α- and β-phosphates, but individual lower fractions of this mixture can also be used. For these reasons, it is recommended that the emulsion according to the invention contains dinatriglycerophosphates as organic phosphates.

It goes without saying that the proposed buffer system of caustic soda and phosphate must be added to the emulsion in a quantity sufficient to achieve the desired effect. It has been established that the desired stabilizing action occurs when the emulsion contains 2 to 10 mmol/1, preferably 3 to 8 mmol/1 of inorganic and/or organic phosphate; and 0.2 to 5 mmol/1, preferably 0.5 to 3 mmol/1 sodium hydroxide, all in relation to the volume of the finished emulsion. Appropriate tests have shown that by changing the ratio of phosphate buffer and caustic soda, as well as their total amount in the emulsion, the desired size of particles in the internal phase can be achieved, while each of the ratios and the total amount of the buffer system must remain within the empirically determined, above-mentioned limits .

Tests have shown that, without adversely affecting the excellent heat stability and storage of the emulsion according to the invention, a particularly good X-ray contrast effect is achieved if the droplets of iodinated fatty acid esters as the internal phase have a mean diameter of at least 0.6 μm. An emulsion according to the invention in which the droplets of iodinated esters have a mean diameter in the range of 0.8 to 3.0 μm is recommended, and an emulsion with droplets of iodinated fatty acid esters having a mean diameter in the range of 0.8 to 2.5 is particularly recommended μm, because they have an extremely good X-ray contrast effect with exceptional heat and storage stability.

The production of the emulsion according to the invention is carried out in a manner known in principle from DE-PS 37 22 540 (see especially column 13/14), whereby during the entire process and possibly the subsequent storage of the finished emulsion, care is taken that the components and resulting mixtures, as well as finished emulsion, are constantly kept in a nitrogen atmosphere. The individual stages of the procedure can be briefly described as follows:

First, the necessary amounts of lecithin are added, with constant stirring, to an appropriate amount of distilled water (aqua injectabilia), heated to approx. 55 to 60°C, and then the mixture is continued to be stirred for some time, for example 15 to 20 minutes.

Parallel to this, appropriate amounts of glycerine and sodium trimolate are added, with constant stirring, to an appropriate amount of distilled water, heated to about 55 to 60°C, and dissolved. The resulting solution is then filtered, in a pressurized nitrogen atmosphere, through a suitable membrane filter, e.g. with a pore size of 0.2 μm, and the filtrate is added to the previously prepared mixture of water and lecithin, while the temperature is still maintained at 55 to 60° C.

A metered amount of iodinated fatty acid esters, e.g. ethyl ester of fatty acids from iodized poppy seed oil, is heated to 50 to 60°C and filtered through a nylon membrane filter, with pores of e.g. 0.2 μm, and the filtrate is directly added to a previously prepared aqueous mixture of lecithin, glycerin and sodium molyate, with constant mixing, and for example, with the use of a mechanical high-frequency device (Ultra-Turrax) together with a mixer, whereby a rough emulsion is formed. After the final addition of iodized oils, the produced rough emulsion will be emulsified for some time, in order to obtain a suitable pre-emulsion. In doing so, the entire mixture will be constantly kept at 55 to 60°C and covered with nitrogen.

The obtained preemulsion will be further emulsified in a two-stage homogenizer, at 400 bar in the first stage, and at 100 bar in the second stage, maintaining a temperature between 50 and 60°C. After performing homogenization under high Mak, the emulsion is drained into a storage tank. There, the emulsion is diluted to a suitable concentration by adding appropriate amounts of phosphate buffer and caustic soda. At the same time, the emulsion is cooled to about 10 to 15°C. After that, the emulsion is raised in a protective nitrogen atmosphere, after which it is heat sterilized in a rotary autoclave at 121°C for 15 minutes.

Emulsions according to the invention must be protected from light and oxygen after exposure, which is why exposure is carried out in a nitrogen atmosphere. After sterilization, the emulsion was poured out and kept in storage at +4 and 21°C. After storage for 14 and 35 days, tests showed that the emulsion did not change during that time.

The invention will be explained in more detail through the following examples:

Example 1

The oil-water emulsion according to the invention of the X-ray contrast agent is made in the following way:

First, 231 ml of distilled water for injection was poured into a container filled with nitrogen and heated to 55 to 60°C, and this temperature was maintained during the following stages of the procedure. The water was mixed with nitrogen until the oxygen content fell below 0.1 mg/l. After that, in the presence of a nitrogen atmosphere, 16 g of egg lecithin, E80, was added to the water for two minutes and with constant mixing and with the high-frequency device (Ultra-Turrax) turned on, it was crushed in a mixer and mixed for another 15 minutes.

In parallel with that, 75 ml of distilled water for injections was heated to a temperature of 55 to 60°C in another container filled with nitrogen, and maintained at that temperature during the following stages of the procedure. Here, too, nitrogen was introduced into the water until the oxygen content fell below 0.1 mg/l. After that, 25 g of glycerine (100% - nog) and 0.3 g of sodium oleate were added to the water and dissolved slowly, with stirring. The resulting solution, heated to 55 to 60°C, was added to the prepared mixture of water and lecithin in a pressurized nitrogen atmosphere for 10 minutes through a membrane filter with openings of 0.2 μm.

200 g of ethyl ester of fatty acids of iodized poppy oil (trade name Lipiodol UF) was heated in a vessel with a nitrogen atmosphere to 50 to 60°C and through a nylon membrane filter, pore size of 0.2 μ, directly added for 20 to 25 minutes, into the prepared aqueous mixture of lecithin, glycerin and natrioleate with constant stirring, while the mixture was simultaneously processed with one high-frequency device (Ultra-Turrax) by turning on one fine generator (G6) and one coarse generator (G2). After the addition of the X-ray contrast medium, the rough emulsion obtained was emulsified for another 25 minutes. During the preparation of the rough emulsion, it was maintained at a temperature in the range of 55 to 60°C and was constantly covered with nitrogen.

After turning off the mechanical high-frequency device, the coarse emulsion, with gentle stirring, was poured through a membrane filter with an average pore size of 40 μm (trade mark HDC H 400) in a nitrogen atmosphere under a pressure of about 0.5 bar into a two-stage homogenizer (Gaulin - two-stage homogenizer) for the production of fat emulsions, and there it is homogenized in the first stage at 400 bar and in the second stage at 100 bar. The required pressure for homogenization was achieved with hot distillate via a bypass line. It was then redirected to an emulsion.

During homogenization, the temperature was around 60°C. The resulting emulsion was taken to a storage tank where it was covered with nitrogen. Here the emulsion is left to stand with occasional gentle stirring.

The emulsion was then subjected to two subsequent stages of homogenization, where the temperature was still maintained at around 60°C. After the fourth stage of homogenization, the emulsion was cooled as quickly as possible and poured into one collector, which contained 500 ml of oxygen-free distilled water cooled to 12°C and 0.89 g of disodium hydrogen phosphate × 2H2O. During the pouring of four times homogenized emulsion into the collector, it is no longer mixed with nitrogen but is only covered. With occasional gentle stirring, the emulsion was then cooled to 8 to 9°C. When this temperature is reached, the mixer is switched off.

The pH value of the emulsion was checked. Deviations from the preset value (pH value from 10.0 to 10.2) were corrected by adding 2.2 ml of i n sodium hydroxide solution. The resulting emulsion was stored in a cooling tank in a nitrogen atmosphere, and before extraction it was filtered through a membrane filter with pores of 2 to 8 μm, with an extraction pressure of no more than 0.5 bar. The extraction was carried out in a nitrogen atmosphere in gas fusion bottles (quality class II), where it was mixed with nitrogen, so that the oxygen content in the glass bottles was less than 0.1 mg/l. After filling, the bottles are closed with rubber caps with a metal coating that is attached by deforming.

According to the invention, the emulsion had to be protected from light and oxygen during production and storage.

The emulsion poured into gas fusion bottles was then sterilized by heat in rotary autoclaves at 121°C for 15 minutes. Before sterilization, the emulsion had a pH value of 10.0, and after sterilization, the pH value was 7.1. The density of the emulsion before and after sterilization was 1.046. The osmolality of the emulsion was 278 mosm/1.

Optical inspection showed that the obtained emulsion, both before and after sterilization, met the usual criteria for an oil-water emulsion, which can be applied by injection.

Furthermore, the particle size distribution in the emulsion was determined before sterilization by dynamic light dispersion (Autosizer 2c, Malvern company) and after sterilization using the Coulter method. These measurements were made with the measuring kit "Elzone" of the company Particle Data.

The following results were obtained:

Table 1

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After sterilization, the bottles are filled with emulsion, protected from light, kept in storage at a temperature of +4°C and 21°C. Sampling showed that the emulsion, after being kept in storage for 14 or 35 days, was unchanged and in good condition, and that the partially deposited droplets could be dispersed again, unchanged, by lightly shaking the bottles.

Examples 2 to 9.

Other oil-water emulsions of one X-ray contrast agent were made in the manner described in more detail in Example 1, which have the structure described later and differ only in the type and amount of added buffer system. For the sake of comparison, as example 2, an emulsion was made without a buffer system, which could not, which is self-evident, be sterilized by heat, so its particle size distribution was determined in an unsterilized state, while in the case of emulsions from examples 3 to 9, the distribution particle sizes measured after sterilization in autoclaves for 15 minutes at 121°C.

The emulsion described in examples 2 to 9 had the following composition per 1000 ml:

16 g of egg lecithin, E 80

25 g of glycerin (100% pure)

0.3 g of sodium oleate

193.5 g ethyl ester of fatty acids of iodized poppy oil (Lipiodol UF)

820 ml of distilled water.

The following buffer system was added to the emulsion of this composition after the fourth phase of homogenization and subsequent cooling of the emulsion to about 12°C:

Example 2: without a buffer system

Example 3: 5 mmol/1 Na2HPO4 × 2 H2O + 0.68 mmol/l NaOH

Example 4: 5 mmol/1 Na2HPO4 × 2 H2O + 1.2 mmol/l NaOH

Example 5: 5 mmol/1 Na2HPO4 × 2 H2O + 1.5 mmol/l NaOH

Example 6: 5 mmol/1 Na2HPO4 × 2 H2O + 2.2 mmol/l NaOH

Example 7: 5 mmol/l sodium glycerophosphate + 1.1 mmol/l NaOH

Example 8: 5 mmol/l sodium glycerophosphate + 1.38 mmol/l NaOH

Example 9: 5 mmol/l sodium glycerophosphate + 2.13 mmol/l NaOH

The obtained emulsions were shown to be correct during the optical inspection as a whole. The following tabular overview (Table 2) shows the pH values before and after sterilization (example 2 only before sterilization) as well as the particle size distribution, measured by the Coulter method, for the emulsion from example 2 in the unsterilized state, and for the emulsions from example 3 to 9 after addition of buffer and sterilization, and as a measure of sterilization of emulsions, their zeta-potential.

The results from Table 2 show very clearly how the particle size distribution, under the same production conditions, after the addition of the buffer system and subsequent sterilization at 121°C, shifts very noticeably from smaller particles (example 2) to larger particles (examples 3 to 9). Zeta-potential indicates that the added buffer system always achieves the desired effect.

Table 2.

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+ Average particle size measured by dynamic light dispersion (Autosizer 2c, Firme Malvern) 264 nm

* Buffer system: Na2HPO4 + NaOH;* Buffer system: sodium glycerophosphate + NaOH

Claims (7)

1. Oil-water emulsion of an X-ray contrast agent, with an internal phase of one or more oil-soluble iodine compounds, especially iodinated esters of fatty acids, possibly together with one or more highly refined glyceride oils, one or more emulsifiers or possibly co-emulsifiers, indicated by , which contains one physiologically tolerable sodium hydroxide buffer and one or more inorganic and/or organic phosphates. 2. Emulsion according to claim 1, characterized in that it contains disodium hydrogen phosphate as an inorganic phosphate. 3. Emulsion according to claim 1 or 2, characterized in that it contains disodium glycerophosphates as organic phosphate. 4. Emulsion according to one of the claims from 1 to 3, characterized by the fact that it contains 3 to 8 mmol/1 of inorganic and/or organic phosphate and 0.5 to 3 mmol/1 of caustic soda, relative to the volume of the finished emulsion. 5. Emulsion according to one of claims 1 to 5, characterized in that the droplets of iodinated fatty acid esters as the internal phase have a mean diameter in the range of 0.6 to 4.0 μm. 6. Emulsion according to claim 5, characterized in that the droplets of iodinated fatty acid esters have a mean diameter in the range of 0.8 to 3.0 μm. 7. Emulsion according to claim 5, characterized in that the droplets of iodinated fatty acid esters have a mean diameter in the range of 0.8 to 2.5 μm.