Perfluorocycloamine Emulsion Preparation

The present invention relates to therapeutical fluorocarbon emulsions having oxygen carrying ability to be used for life-saving of massively bleeding patients, storage of an organ involved in the transplantation of the organ, etc.

It has already been reported that the fluorocarbon emulsions possess the possibility of being used as red cell substitutes for mammals and as organ storing perfusates for transplantation of organs, especially as transfusions for the purpose of performing the oxygen carrying ability [Leland C. Clark, Jr., Becattini, F., Kaplan, S., The Physiology of Synthetic Blood, Journal of Thoracic Cardiovascular Surgery, Vol. 60, p. 757-773, 1970; Geyer, R. P., Fluorocarbon--Polyol Artificial Blood Substitutes, New Engl. J. Med., Vol. 289, p. 1077-1082, 1973].

However, the previously known fluorocarbon emulsions cannot be said practical because of their pharmaceutical instability, and it is necessary to develop a stable preparation in which the particle diameter does not change for a prolonged time in order to put the fluorocarbon emulsions into practical use as artificial red cells.

In the fluorocarbon emulsions, the size of the particles plays a important role on the toxicity and efficacy of the emulsion. [Yokoyama, K., Yamanouchi, K., Watanabe, M., Murashima, R., Matsumoto, T., Hamano, T., Okamoto, H., Suyama, T., Watanabe, R., Naito, R., Preparation of Perfluorodecalin Emulsion, an Approach to the Red Cells Substitute, Federation Proceeding, Vol. 34, p. 1478-1483, May, 1975]. In other words, the emulsion having a large particle diameter has high toxicity and also the retention time of the particles in the blood stream is short. Therefore, when a fluorocarbon emulsion is employed as artificial red cells for a life-saving transfusion for massively bleeding patients, the particle diameter of the emulsion particles should be 0.3.mu. or less, preferably 0.2.mu. or less [Japanese Patent Application "Kokai" (Laid-open) No. 22612/1973]. Apart from the particle diameter, in order to use a fluorocarbon for the purpose of artificial red cells, the fluorocarbon administered into the vein must be rapidly eliminated out of the body after finishing the original purpose of the oxygen transport (U.S. Pat. No. 3,911,138, Leland C. Clark, Jr.). Dr. Clark named such compounds as reticuloendothelial-system (RES) phobic fluorine-containing organic compounds, and distinguished these compounds from RES philic compounds which are characterized by the presence of an atom such as oxygen or nitorgen in their structure or by their heterocyclic nature.

The present inventors have conducted extensive strudies on an enormons number of compounds including perfluoro compounds of the general formula: ##STR2## wherein either or both of Ring A and Ring B may optionally be substituted with lower perfluoroalkyl group(s), m and n each represents 4, 5 or 6 and Z represents a perfluoroalkylene group or a mere bond, and found that specific compounds included within the compounds, which are named as RES-philic compound by Dr. Clark, represented by the formula (I), i.e. the perfluorocycloamines of the general formula: ##STR3## wherein any position may optionally be substituted by a perfluoromethyl group can yield long-term stable emulsions having extremely fine particles and moreover said compounds are unexpectedly excellent in the properties of elimination. Thus, the present invention has been accomplished.

An object of the present invention is to provide a therapeutical fluorocarbon emulsion preparation having oxygen carrying ability containing a compound represented by the above-mentioned general formula of (II) as an oxygen carrying component.

Other objects and advantages of the present invention will be apparent from the following descriptions.

In relation to the general formula (II), while the substitution position of the perfluoromethyl group is not particularly restricted, it is preferred that the number of the substituents is one.

The therapeutical perfluorocarbon emulsions having oxygen carrying ability are known per se in the art, and hence the feature of the present invention resides in the selection of the specific perfluoro-compounds, i.e., the compounds of the general formula (II) as the perfluorocarbon compound. Therefore, as the perfluorocarbon emulsion preparations themselves in the present invention, those similar to the previously known products may be contemplated. That is, they are oil-in-water emulsions in which a perfluoro-compound is dispersed in water, and the amount of the perfluoro-compound to be incorporated is 5-50% (w/v), preferably 10-40% (w/v).

On preparing an emulsion, a polymeric nonionic surfactant, a phospholipid and the like are employed each alone or in combination thereof as an emulsifying agent, and its amount to be added is 1-5% (w/v).

The polymeric nonionic surfactant used herein is that having a molecular weight of 2,000-20,000, and examples thereof include polyoxyethylene-polyoxypropylene copolymers, polyoxyethylene fatty acid esters, polyoxyethylene castor oil derivatives, etc., and examples of the phospholipid include, vitelline phospholipid, soybean phospholipid, etc.

In addition, if necessary, it is also possible to add as an emulsifying agent, for example, a fatty acid having 8-22 carbon atoms, particularly 14-20 carbon atoms, or a physiologically acceptable salt thereof [e.g. alkali metal salts such as sodium salt, potassium salt, etc., monoglycerides thereof]. Examples of the above fatty acid include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, palmitoleic acid, oleic acid, linoleic acid, arachidonic acid, sodium or potassium salts thereof, their glycerides, etc. The amount thereof to be added is 0.001-0.1% (w/v).

As the medium, a physiologically acceptable aqueous solution, for example, physiological saline, lactic acid added Ringer's solution, etc., may be employed.

If necessary, there may be added an isotonizing amount of an isotonizing agent such as glycerol to isotonize the emulsion, and a plasma extender such as hydroxyethylstarch, dextran etc. to adjust the colloid osmotic pressure of the emulsion.

The emulsions of the present invention may be prepared by mixing the respective components in any order, coarsely emulsifying and homogenizing by using an appropriate emulsifier (e.g. a Manton-Gaulin type emulsifier) until the particle diameter becomes 0.3.mu. or less.

Further, the compound of the general formula (II) can be produced by fluorinating a perhydrocompound corresponding to the compound of the general formula (II). As the fluorination method, there may be mentioned, for example, known fluorination methods such as the direct fluorination method, the cobalt fluorination method, the electrolytic fluorination method, etc.

In the production of the compound (II), the use of the electrolytic fluorination method is preferable. The method can be carried out, for example, by adding into an electrolytic cell anhydrous hydrofluoric acid and a perhydrocompound as raw material compound, making them a solution by mixing and thereafter subjecting the solution to electrolysis. Normally, the voltage used in the electrolysis is 3 to 9 V, the anode current density is 1 to 300 A/dm.sup.2 and the cell temperature is 4.degree. to 10.degree. C.

The compound of the general formula (II) thus formed, being insoluble in anhydrous hydrofluoric acid, precipitates at the bottom layer of the electrolytic cell.

The isolation and refining of the compound of the general formula (II) from the precipitate is carried out, for example, by adding to the recovered precipitate a mixture of an equal volume of an aqueous alkali solution and an amine compound, subjecting the whole mixture to refluxing, then separating the compound (II) of the lowermost layer (at this time, partially fluorinated compounds are dissolved in the mine layer), washing the compound (II) with an appropriate amount of aqueous acetone solution containing potassium iodide to remove compounds having nitrogen atoms combining with fluorine atoms, and thereafter conducting a fractional distillation to collect the compound of the general formula (II).

The perfluorocycloamine emulsion preparations according to the present invention have oxygen carrying ability, and thus are employed a, for example, transfusions for oxygen transport (the so-called red cell substitutes), organ storing perfusates, etc.

When the perfluorocycloamine emulsion preparation of the present invention is employed as, e.g., a transfusion for oxygen transport, it is generally administered by intravenous injection, and the dosage for a human adult is 50-2,000 ml per dose.

As an electrolytic cell, a tank (made of Monel metal) having a capacity of 1.5 l, containing electrodes made of nickel (purity of 99.6% or higher) (6 anodes and 7 cathodes) alternately arranged with an electrode gap of 1.7-2.0 mm with an effective anode surface area of 10.5 dm.sup.2 and further equipped with a reflux condenser made of copper above the tank was employed.

To this electrolytic cell was introduced 1.2 l of anhydrous hydrofluoric acid, and the impurities (water and sulfuric acid) present in very small amounts were removed by the preliminary electrolysis. Thereafter, 0.85 mole (130 g) of N-cyclohexylpyrrolidine was dissolved in the anhydrous hydrofluoric acid, and while passing helium gas at a flow rate of 100 ml/min. from the lower part of the cell, the electrolysis was effected with an anode current density of 1.0-2.0 A/dm.sup.2, a voltage of 4.0-6.2 V and a bath temperature of 4.degree.-10.degree. C. The electrolysis was continued for 1051 A.multidot.hr until the electrolytic voltage reached 9.0 V. Anhydrous hydrofluoric acid was additionally introduced 200 ml per 24 hours. The gas generated during the electrolysis was passed through an iron tube packed with sodium fluoride pellets to remove the entrained anhydrous hydrofluoric acid, and then led into a trap cooled with dry ice-acetone to liquefy and trap to obtain 9.5 g of a colorless liquid. On the other hand, the bath solution in the electrolytic cell separated into two phases, the upper layer containing hydrogen fluoride and the lower layer fluoro-compound. The lower layer was separated and weighed 263 g.

The liquid collected by cooling the above generated gas and the lower layer liquid of the electrolytic cell were combined, 70% KOH aqueous solution and diisobutylamine were added thereto in equal volumes, and refluxing was conducted for 7 days. The perfluoro product was separated with a separatory funnel, washed with 90% (w/v) acetone aqueous solution containing 10% (w/v) of potassium iodide, then subjected to fractional distillation using an apparatus for fractional distillation equipped with a spinning band column to obtain 44 g (yield 8%) of perfluoro-N-cyclohexylpyrrolidine (b.p. 145.degree.-152.degree. C./760 mm Hg). Said compound was confirmed to be the desired compound perfluoro-N-cyclohexylpyrrolidine as the result of the infrared absorption spectrum, F-nuclear magnetic resonance spectrum, and mass spectrum.

The following perfluoro-compounds were prepared similarly as in Reference Example 1.

Perfluoro-N-(3'-methylcyclohexyl)pyrrolidine (b.p. 156.degree.-165.degree. C./760 mm Hg)

Perfluoro-N-cyclohexyl-2-methylpyrrolidine (b.p. 156.degree.-165.degree. C./760 mm Hg)

Perfluoro-N-cyclohexyl-3-methylpyrrolidine (b.p. 156.degree.-165.degree. C./760 mm Hg)

Perfluoro-N-(2'-methylcyclohexyl)pyrrolidine (b.p. 156.degree.-165.degree. C./760 mm Hg)

Perfluoro-N-(4'-methylcyclohexyl)pyrrolidine (b.p. 156.degree.-165.degree. C./760 mm Hg)

The present invention is further illustrated below with reference to the Examples and Experimental Examples but the invention is not limited thereto.

400 g of vitelline phospholipid was added to 8.5 l of lactic acid added Ringer's solution, and stirred by a mixer to prepare a coarse emulsion, then 2.5 kg of perfluoro-N-cyclohexylpyrrolidine was added thereto and stirred vigorously again by the mixer to prepare a coarse emulsion. This coarse emulsion was placed in a liquid tank of a jet emulsifier (manufactured by Manton-Gaulin Co.) and circulated while maintaning the liquid temperature at 50.degree. C..+-.5.degree. C. to effect emulsification. The concentration of perfluoro-N-cyclohexylpyrrolidine in the obtained emulsion was 27.3% (w/v). The particle diameter as measured by the centrifugal sedimentation method was 0.05-0.25.mu.. This emulsion was allotted into vials for injection, stoppered and thermally sterilized in a rotary sterilizer, but there was no significant increase in the particle diameter observed.

An emulsion was obtained by procedures similar to those in Example 1 except that perfouro-N-cyclohexylpyrrolidine was replaced by perfluoro-N-(3'-methylcyclohexyl)pyrrolidine. The particle diameter of the thus obtained emulsion was 0.05-0.25.mu..

Water was added to 20 g of each perfluorocycloamine selected in the present invention and 4 g of vitelline phospholipid to make the total volume 200 ml, and emulsification was effected using a Manton-Gaulin emulsifier as used above under nitrogen stream at 200-600 kg/cm.sup.2 while maintaining the liquid temperature at 40.degree.-45.degree. C. Each obtained emulsion was filtered through a 0.65.mu. membrane filter, allotted into 20 ml capacity vials, and, after replacing the atmosphere by nitrogen gas, thermally treated at 100.degree. C. for 30 minutes, followed by storing at 4.degree. C. of room temperature to examine the stability. The particle diameter of the emulsion was measured by the centrifugal sedimentation method by Yokoyama et al. [Chem. Pharm. Bull. 22 (12) 2966 (1974)], and from the obtained data, the average particle diameter distribution was calculated using a microcomputer.

Thus, the particle diameter distributions of each perfluorocarbon emulsion before and after heating, and after heating and storing at 4.degree. C. and room temperature (15.degree.-28.degree. C.) are shown in Tables 1 and 2. As is evident from the results, the emulsions according to the present invention are very stable against heating and the influence on the average particle diameter due to heating was not observed at all. Further, when stored at 4.degree. C. after heating, there was no increase in the average particle diameter of the emulsion observed even after 5 months.

The acute toxicity test on the preparations of the present invention was carried out using the preparations of the present invention shown in Table 3 which had been physiologically isotonized. The test animals used were Wister-strain male rats (weighing 100-120 g). The emulsion was intravenously administered and the animals were observed for one week after the administration.

The results are such that with either emulsion containing perfluoro-N-cyclohexylpyrrolidine or perfluoro-N-(3'-methylcyclohexyl)pyrrolidine, there was no death case at 100 ml/kg-body weight and thus their toxicity are very small.

Using Wister-strain male rats weighing 120-130 g, the emulsion prepared in Example 1 was administered into the tail vein [at 4 g/kg as perfluoro-N-hexylpyrrolidine], and for a period of 3 months after the administration, the content of said compound in the liver, spleen and fat tissue due to uptake were measured by means of gas chromatography.

The content of perfluoro-N-hexylpyrrolidine uptake in each organ 1, 2 and 4 weeks and 3 months after the administration are shown in Table 4. The compound was taken up in greater amounts by the reticulo-endothelial organs shortly after the administration, but soon disappeared rapidly. There was no evidence of adverse influence on the liver or spleen organ.

As a result, the half-life of perfluoro-N-hexylpyrrolidine was calculated to be 16 days.

Wister-strain male rats weighing 120-130 g were administered with 4 g/kg of the perfluorocycloamine emulsion prepared in Example 1 or Example 2, and the dissected organs were observed for a period of 3 months after the administration, and further the organs (liver and spleen) were weighed, to determine the weight relative to the body weight.

One, 2 and 4 weeks and 3 months after the administration of the emulsion, the important organs, e.g. the lung, liver and spleen were observed, to find no evidence of the influence on the organs by either said compound because of their rapid elimination.