ARTIFICIAL LUNG SURFACTANT AND REMEDY FOR RESPIRATORY DISTRESS SYNDROME CONTAINING IT AS ACTIVE PRINCIPLE

Abstract: An artificial lung surfactant comprising (a) phosphatidyl choline and cardiolipin and/or phosphatidyl glycerol in ad­ dition as phospholipids, wherein the content of said phos­ pholipids is 80 to 95 wt % of the whole composition, (b) neu­ tral lipids, wherein the content is 5 to 20 wt % of the whole composition, and (c) fatty acids, wherein the content is 0 to 10 wt % of the whole composition, and a remedy for the res­ piratory distress syndrome containing said surfactant as an active principle.

Description: Background of the invention The present invention relates to an artificial lung surfactant having surface activity similar to that of natural lung surfactant and to a composition for treating respiratory distress syndrome containing said artificial lung surfactant as the active principle. There exists in alveoli of animal lungs a physiologically active substance, which is called lung surfactant, mainly comprising phospholipid. This substance covers the inner walls of alveoli of the lung to protect the alveolar epithelium and also performs an important physiological function for animals in maintaining their respiratory functioning. More particularly, the lung surfactant is regarded as a substance having a specific surface-active function to change the surface tension of the inner walls of alveoli of the lung corresponding to the exhalation and inhalation of breath and also contributing to the maintenance of interalveolium functional stability to exercise an antiatelectatic action. After years of research conducted by medical circles with the use of various animals with regard to the lung surfactant, detailed particulars of its activities are now being made clear step by step. It has become apparent that this active substance contains phospholipids, neutral lipids, protein as ingredients and that its main constituent is dipalmitoyl lecithin which is known as one of the phospholipids. T. Fujiwara et al recently reported that they obtained an artificially prepared lung surfactant having higher surface activity by adding dipalmitoyl lecithin to a surfactant recovered from bovine lung and that they achieved good results for the therapy of infantile respiratory distress syndrome (IRDS) by the installation of a dispersion of said lung surfactant to the respiratory tracts of premature babies (Pediatric Clinics, Vol. 32, No. 7, p. 1343, 1979). Also Kobayashi et al obtained a lung surfactant prepared from an active substance isolated from swine lung washings, in which Ca⁺⁺ were made to coexist to enhance activity, and successfully achieved a good result for the substitution therapy of IRDS (Journal of Japanese Medical Society for Biological Interface Vol. 12, No. 1, 1981). In these methods, it is intended to extract phospholipid only from the natural lung surfactant following the Folch procedure, wherein organic solvent soluble substances are extracted by use of a mixed solvent consisting of chlorform and methanol and foreign bovine and swine protein is eliminated; however, the elimination is incomplete and the intermixture of foreign protein up to about 1 to 3% in the obtained phospholipid is observed. Also, the existence of protein, which is suitable for the lung but different from ordinary serum albumin, in the naturally obtained lung surfactant is recognized by King et al. (King S. Am. J. Physiol. 224 788∼795, 1973. Fed. Proc. 33 2238∼2241, 1974). It is known that this is a liposoluble protein, which is mainly of molecular weight 34,000 and contains hydrophobic amino acids in large quantities. From the facts mentioned in the above, it is considered that where lung surfactant is prepared from lipids extracted from the native lung surfactant according to the Folch procedure, not only desired phospholipid, neutral lipids, but also protein suitable for the lung are extracted and contamination by such protein is regarded as inevitable. The existence of such protein in lung surfactant is not desirable from the medical viewpoint, since it gives strong probability of causing the manifestation of anti-genecity and side effects including anaphylaxis. With the purpose of overcoming the abovementioned defects, C. J. Morley et al. attempted the preparation of an artificial lung surfactant containing no foreign protein and succeeded clinically in its application to IRDS (The Lancet, January 10, 1981). However, this artificial surfactant is prepared in the form of powder containing dipalmitoyl phosphatidyl choline and phosphatidyl glycerol at the weight ratio of 7:3 and its administration limited to powder administration which presents some technical difficulty found with the administration of powder to the alveoli. DE―A―2,900,3000 (Klitzing) discloses a medicament for treating IRDS comprising dipalmitoyl phosphatidylcholine as the active ingredient. This is preferably provided as an emulsion. Ikegami, M. et al, in Pediatrics Research, 1979, 13(6), 777―780, describes experiments using combination of two phospholipids, for instance a combination of dipalmitoyl lecithin and phosphatidyl glycerol, for improving lung pressure in surfactant depleted adult rat lungs. Meban, C., in Pediatrics Research, 1981, 15(7), 1029―1031, suggests the use of a mixture of dipalmitoyl phosphatidyl choline and either dipalmitoyl phosphatidyl glycerol or phosphatidyl inositol for the treatment of IRDS. As the result of strenuous research work to develop an artificial lung surfactant which does not contain any foreign protein, which has easily obtainable compounds as its ingredients, and which possesses such physicochemical property as specific surface activity peculiar to lung surfactant including, for instance, instantaneous dispersibility into the interface between gas and liquid, the ability to form a stable interfacial layer, and capability of lowering the surface tension to 10 dyne/cm or less, the inventors of the present invention have found that a certain specific compound has a peculiar surface activity and shows excellent physiological efficacy in tests made in vivo on rabbits which have undergone pulmonic irrigation. Accordingly, the present invention provides artificial lung surfactant which is free of protein and comprises: (a) from 80 to 95% by weight of the whole composition of a mixture of (i) a phosphatidyl choline of the formula (I) and (ii) at least one of a cardiolipin of the formula (II) and a phosphadityl glycerol of the formula (III) wherein R₁, R₂, R′₁, R′₂, R′₃, R′₄, R″₁ and R″₂ are straight chain fatty acid acyloxy radicals having 14 to 25 carbon atoms and M is a cation; (b) from 5 to 20% by weight of the whole composition of a neutral lipid having straight chain saturated fatty acid acyloxy radicals having 14 to 25 carbon atoms; and (c) from 0 to 10% by weight of the whole composition of a straight chain fatty acid having 14 to 25 carbon atoms. The present invention also provides a composition for treating respiratory distress syndrome containing the artificial lung surfactant of the present invention as its active principle. Figure 1 shows a diagram of surface area versus surface tension of the artificial lung surfactant. Figure 2 and Figure 3 show changes in partial pressure (1 mmHg is equivalent to 1.33 mbar) of oxygen in the blood with the passage of time resulting from the administration of lung surfactant dispersion to lung lavaged rabbits. The phosphatidyl choline used in the present invention may be either a native L-substance or an artificial DL-substance. As examples of phosphatidyl cholines having straight chain fatty acid acyloxy radicals of 14 to 25 carbon atoms, there are dimyristoyl phosphatidyl choline, dipalmitoyl phosphatidyl choline and distearoyl phosphatidyl choline of which dipalmitoyl phosphatidyl choline is especially desirable. Both native cardiolipins and artificial ones are usable, in the present invention. The native cardiolipins are mainly obtained by extraction from the internal organs such as myocardia, lungs and kidneys of animals such as cattle, horse and swine. Artificial cardiolipins are obtained synthetically, for instance, according to the method proposed by Van Deenen et al. (Advances in Lipid Research, p. 167, Academic Press (1964)). In both cases, said R′₁, R′₂, R′₃ and R′₄ in the formula (II) are straight chain fatty acid acyloxy radicals and it is desirable that part of them are unsaturated ones. Phosphatidyl glycerols used in this invention may be either native L-substances or artificial DL-substances. R″₁ and R″₂ in the formula (II) should be straight chain fatty acid acyloxy radicals having 14 to 25 carbon atoms. As examples of saturated fatty acids from which the radicals can be derived there are myristic acid, palmitic acid and stearic acid. Dipalmitoyl phosphatidyl glycerol is especially desirable. As examples of unsaturated fatty acids from which the radicals can be derived oleic acid and linoleic acid may be mentioned. As neutral lipids used in the present invention, there are triglycerides, diglycerides and monoglycerides of which triglycerides or diglycerides whose main ingredients are saturated straight chain fatty acid acyloxy radicals having 14 to 25 carbon atoms are desirable. As examples of neutral lipids, there are trimyristin, tripalmitin, tristearin, triarachidin, dimyristin, dipalmitin, distearin, diarachidin, trilinolein, triolein, dilinolein, and diolein. Fatty acids used in this invention are preferably those straight chain fatty acids such as myristic acid, palmitic acid, stearic acid, and arachidic acid, as saturated fatty acids, and oleic acid, elaidic acid, linoleic acid and linolenic acid, as unsaturated fatty acids. The phospholipids to be contained in the artificial lung surfactant of the present invention, may comprise a combination of phosphatidyl choline and cardiolipin, a combination of phosphatidyl choline and phosphatidyl glycerol, or a combination of phosphatidyl choline, cardiolipin, and phosphatidyl glycerol. These phospholipids represent 80 to 95 wt% of the whole composition, desirably 85 to 90 wt%. The neutral lipids represent 5 to 20 wt% of the whole composition, desirably 5 to 10 wt%, and the fatty acids represent 0 to 10 wt% of the whole composition, desirably 0 to 5 wt%. If the above-mentioned instructions as to the content of main ingredients are not observed, the object of the present invention can not be achieved. In the present invention, it is especially desirable to have the artificial lung surfactant contain a phosphatidyl choline which possesses two saturated straight chain fatty acid acyl radicals having 14 to 25 carbon atoms, representing 55 to 80 wt% of the whole composition, 9 phosphatidyl glycerol which possesses two straight chain fatty acid acyl radicals having 14 to 25 carbon atoms, representing 10 to 35 wt% of the whole composition, and neutral lipids representing 5 to 20 wt% of the whole composition. In the present invention, other phospholipids, carbohydrates, etc. may be contained as ingredients in addition to the abovementioned ones to such an extent as not to degrade the surface activity of the artificial lung surfactant. The artificial lung surfactant of this invention can be obtained by homogeneously mixing said phosphatidyl choline and cardiolipin and/or phosphatidyl glycerol. No limit is set to the method and means of mixing; however, to cite one example, a homogeneous mixture can be prepared easily by dissolving the ingredients in a common solvent such as chloroform, and then removing the solvent from the solution. The artificial lung surfactant thus obtained is usually a wax and when its surface activity is measured by use of a Wilhelmy balance as mentioned later, its minimum surface tension value is 10 dyne/cm or less and its maximum surface tension value is 36 to 70 dyne/cm. Its stability index is 1.2 or more. These values generate a specific hysteresis loop as shown in Figure 1 similar to that of natural lung surfactant to indicate that the obtained artificial lung surfactant has a high surface activity. Since the artificial lung surfactant of this invention is usually obtained as a wax, it is advisable to administer it by dispersing it in water or an electrolytic solution such as saline solution or by forming it into a powder by use of other medically permissible powders as excipients. The preparation of a dispersion can be achieved by dispersing the waxy surfactant directly in a liquid; however, for reasons of sanitation and preparing procedure, a powder may be prepared beforehand by lyophilizing a dispersion of said waxy surfactant in a solution containing an excipient, as case may require. The thus formed powder is then dispersed in water at the time of its administration. As medically permissible powders, those powders which are water-soluble and innocuous are desirable and it is proper to use it at a ratio of 2 to 50 parts by weight against 1 part by weight of the artificial lung surfactant, especially 5 to 20 parts by weight is recommendable. As desirable powders, amino acids and saccharides may be mentioned because they do not degrade the surface activity. As the amino acids, there are essential amino acids such as glycine, alanine, tryptophane and cystine, and as the saccharides, there are glucose, mannitol and sorbitol. As the methods of preparing a powder, it can be prepared simply by thoroughly mixing the artificial lung surfactant with medically permissible powders. However, it is preferable to prepare a powder by dissolving the surfactant in an organic solvent, to which a proper quantity of fine powder of amino acid was added to obtain a homogeneous dispersion. The obtained dispersion is put into for instance a rotary evaporator and evaporated to dryness under reduced pressure with rotation and stirring. The obtained powder is further pulverized into fine powder of uniform particle size to give a desired powder. In another method of preparing a powder, the surfactant is uniformly dispersed in water or an aqueous solution of salt. A prescribed amount of said saccharide or amino acid is dissolved in the obtained dispersion to prepare a homogeneous dispersion. The dispersion is then lyophilized and the obtained powder is further pulverized into fine powder having a uniform particle size to give the desired powder. The artificial lung surfactant attaches to the surfaces of the powdery substance uniformly and can be used as a preparation having the form of powder. Since the artificial lung surfactant thus prepared in the form of powder makes no change in its surface activity and has the same degree of surface activity as the natural lung surfactant as mentioned herein before, the powder of the artificial lung surfactant of this invention can reasonably be expected to have enough efficacy as a remedy for respiratory distress syndrome such as IRDS, etc when administered by inhalation or nebulization. In the present invention, the measurement of surface tension and the calculation of stability index of the artifical lung surfactant were conducted according to the following procedures. In measuring the surface tension, an improved type of Wilhelmy balance of Acoma make was used. 50 ml of saline solution was put in the Teflon (Teflon is a registered trade mark) trough in the Wilhelm balance and the surface tension of water was adjusted to 72 dyne/cm. In the case where the specimen was a dispersion, the measurement was made after 50 ml of saline solution used in the adjustment was replaced with 50 ml of specimen dispersion. In the case where the specimen was a dry substance or powder, a very small amount of the specimen powder was placed gently on 50 ml of saline solution. The surface film area was compressed cyclically in the range of a maximum of 40 cm² to a minimum of 13 cm² at the rate of 0.3 cycle/min to record a surface area-surface tension diagram as shown in Figure 1 by use of an X―Y recorder. The minimum surface tension (γ min) value, maximum surface tension (γ max), and area surrounded by the hysteresis loop were obtained from the hysteresis loop converged invariantly at the 5th or 6th cycling from the start. The stability index (S.I.) was obtained from the following equation: The measurement of surface activity in vivo was made according to the method proposed by Kataoka et al. (Journal of Japanese Medical Society for Biological Interface 13 (2) 61 (1982)) by means lung-lavage as follows. An adult rabbit had its trachea cut open under an anesthetic and was given lung lavage five times at intervals of 10 minutes with 75 ml of saline solution through a tube inserted from the cut opening into the trachea. The lung lavages were conducted by slowly injecting a saline solution and then sucking up to remove it. When 5 minutes passed after the lavages were over, the rabbit was given 10 ml of a dispersion containing 1 % artificial lung surfactant obtained in the example of the present invention. The treated rabbit was kept under respiratory control by use of a respiratory based on inspiratory intratracheal pressure of 20 cm of mercury and PEEP (positive end expiratory pressure) of 40 mbar (3 cm of mercury) under pure oxygen. For comparison's sake, the same amount of saline solution was administered according to the same method. The following Comparison and Examples, in which percents are by weight, illustrate the invention in detail. Reference 1 Preparation of natural lung surfactant A lung surfactant was separated following the procedure mentioned below which was based on the method proposed by M. E. Abrams (J. Appl. Physiol. 21, 718―720). 2 kg of bovine lung was cut into thin pieces, homogenized in 5 l of saline solution in a homogenizer, and filtered through a gauze to obtain an extract. The extract was subjected to low speed centrifugation at a rate of 1,000 rpm for 30 minutes to obtain a supernatant. The obtained supernatant was centrifuged at a high rate of 7,000 rpm for 60 minutes to give a centrifugate. The centrifugate was dispersed in a saturated saline solution (specific gravity 1.21) which had been prepared and cooled beforehand. The dispersion was centrifuged at a rate of 7,000 rpm for 30 minutes and the upper white layer was collected, which was then dialyzed against cooled distilled water and lyophilized to obtain a natural lung surfactant. In accordance with the procedure proposed by Folch, the obtained natural lung surfactant was dissolved in a mixed solvent of chloroform and methanol (volume ratio 2:1) and the solution was then allowed to stand in contact with a 0.5% saline solution to obtain lipids. It was found that the lipids contained about 2% protein. Its surface activity is shown in Table 1. The lipids were solubilized with SDS and subjected to electrophoresis analysis of polyacrylamide gel disk type according to the ordinary method. A single band was observed at a mobility of 0.72, from which the molecular weight was assumed to be about 35,000 as compared with the mobility of L-chain and H-chain of immunoglobulin used as a control in the same electrophoresis analysis. Example 1 650 mg of L-α-dipalmitoyl phosphatidyl choline (DPPC), 250 mg of L-α-dipalmitoyl phosphatidyl glycerol (DPPG), and 100 mg of tripalmitin were mixed and dissolved in 50 ml of chloroform to obtain a homogeneous solution. The solution was placed in a rotary evaporator and evaporated at room temperature under reduced pressure to dryness and dried further at a high degree of vacuum to obtain a white waxy solid substance. 50 mg of the thus obtained solid substance was dispersed homogeneously in 50 ml of saline solution and its surface activity was determined with the use of an improved type of Wilhelmy balance. The result is shown in Table 1. The hysteresis loop was large (i.e. the area was large) and the minimum surface tension (γ min) was 10 dyne/cm or less. A homogeneous 1% dispersion of the obtained solid substance was prepared to evaluate its effect in vivo when administered to rabbits subjected to lung lavage. As seen from Figure 2, the partial pressure of oxygen (PaO₂) in the blood of the rabbits subjected to lung lavage presented the same rise as the natural lung surfactant to show the recovery of respiratory function. Example 2 600 mg of L-α-DPPC, 300 mg of L-α-DPPG, and 100 mg of tripalmitin were mixed and dissolved in 35 ml of chloroform. The solution was evaporated to dryness according to Example 1 to obtain a white waxy solid substance. Its surface activity was determined according to Example 1 and the obtained result is shown in Table 1. Thereafter, a homogeneous 1% dispersion of this substance was prepared to evaluate its effect in vivo when administered to rabbits subjected to pulmonic irrigation. As shown in Figure 2, the partial pressure of oxygen (PaO₂) in the blood presented the same rise as the natural lung surfactant as in Example 1 to show the recovery of respiratory function. Example 3 750 mg of DL-α-DPPC, 150 mg of L-α-DPPG, and 100 mg of tripalmitin were mixed and dissolved in 35 ml of chloroform. A white solid substance was obtained from the solution according to the same procedure as Example 1. Then 100 mg of this substance was dispersed homogeneously in 50 ml of saline solution and the surface activity was measured with the use of a Wilhelmy balance. The result showed that it had an excellent surface activity as shown in Table 1. Example 4 650 mg of L-α-DPPC, 250 mg of L-α-DPPG, and 100 mg of tristearin were weighed respectively, dissolved in 50 ml of chloroform, and evaporated to dryness to obtain a white waxy substance. The result of the measurement of its surface activity is shown in Table 1 and it showed a hysteresis loop having a large area and the minimum surface tension (γ min) of 10 dyne/cm or less. 500 mg of this substance was dispersed homogeneously in 50 ml of an aqueous solution of 15% mannitol. This dispersion was then lyophilized to obtain a white dry substance. The obtained substance was pulverized in a small-sized ball mill for 20 hours to obtain a fine white powder of uniform particle size. This fine powder had a surface activity as shown in Table 1 and its dispersibility was also very good. Example 5 650 mg of L-α-DPPC, 250 mg of sodium salt of a cardiolipin having an iodine value of 77.7 extracted from bovine hearts, and 100 mg of tripalmitin were weighed respectively, mixed, and dissolved in 30 ml of chloroform to prepare a homogeneous solution. The solution was then put in a rotary evaporator and evaporated to dryness at room temperature under reduced pressure, and further dried under high vacuum to obtain a white waxy solid substance. The iodine value of this substance was 19.3. Thereafter, 100 mg of this substance was dispersed homogeneously in 50 ml of saline solution and its surface activity was measured with the use of an improved Wilhelmy balance. When the specimen dispersion was poured in, the surface tension decreased instantly to show an excellent interfacial adsorbability and presented a hysteresis loop having a large area. The result is shown in Table 2 indicating that it has a surface activity similar to the natural lung surfactant. Also, a homogeneous 1 % dispersion of this substance was prepared to examine its therapeutic effect in vivo by administering it to rabbits subjected to lung lavage along with Reference 1. As shown in Figure 3, the partial pressure of oxygen (PaO₂) in the blood of the rabbits presented the same rise as the natural one to show the recovery of respiratory function. Example 6 600 mg of L-α-DPPC, 250 mg of cardiolipin, 100 mg of tripalmitin, and also 50 mg of palmitic acid were mixed, dissolved in 30 ml of chloroform, and evaporated to dryness according to Example 5 to obtain a white waxy solid substance. This substance had an iodine value of 19.3 and its surface activity was measured according to Example 5. The result is shown in Table 2. Thereafter, a homogeneous 1% dispersion of this substance was prepared to evaluate its therapeutic effect in vivo by administering it to rabbits subjected to lung lavage. As seen from Figure 3, the partial pressure of oxygen (PaO₂) in the blood presented almost the same rise as the natural one to show the recovery of respiratory function. Example 7 550 mg of DL-α-DPPC, 200 mg of ovolecithin (natura phosphatidyl choline), 100 mg of cardiolipin, 75 mg of tripalmitin, and 75 mg of palmitic acid were weighed, dissolved in 30 ml of chloroform, and evaporated to dryness according to Example 5 to obtain a white waxy solid substance. This substance had an iodine value of 23.0. Then, 100 mg of this substance was dispersed homogeneously in 50 ml of saline solution and its surface activity was measured with the use of an improved Wilhelmy balance. The result is shown in Table 2, indicating an excellent surface activity. Example 8 650 mg of DL-α-DPPC, 200 mg of phosphatidyl glycerol, which contains unsaturated fatty acid residues having 14 to 25 carbon atoms, arising from egg yolk lecithin, 100 mg of tripalmitin, and 50 mg of trilinolein were weighed respectively, dissolved in 30 ml of chloroform, and evaporated to dryness according to Example 5 to obtain a yellowish white waxy solid substance. The iodine value of this substance was 24.1. A 0.2% dispersion of this substance was prepared to measure its surface activity by using a Wilhelmy balance according to Example 5. The result is shown in Table 2, indicating that it has an excellent surface activity. Example 9 600 mg of L-α-DPPC, 300 mg of cardiolipin, and 100 mg of tripalmitin were weighed, dissolved in 30 ml of mixed solvent of chloroform and methanol (volume ratio 2/1), and evaporated to dryness to obtain a white waxy substance. It had an iodine value of 28.0 and the result of the measurement of its surface activity is shown in Table 2. It had an excellent adsorbability and described a hysteresis loop having a large area. Also 500 mg of this substance was dispersed homogeneously in 50 ml of water, in which 10 g of mannitol was dissolved to prepare a homogeneous dispersion. The dispersion was lyophilized to obtain a white dry substance. This substance was subjected to pulverization in a small-sized ball mill for 15 hours to give a white powder of uniform particle size. It had a surface activity as shown in Table 2 and its dispersibility was also very good. Example 10 650 mg of L-α-DPPC, 300 mg of sodium salt of cardiolipin, and 50 mg of dilinolein were dissolved in 30 ml of chloroform and evaporated to dryness according to Example 5 to obtain a white waxy solid substance. The surface activity of this substance was measured and is shown in Table 2. Furthermore, this waxy solid substance was dispersed homogeneously in 50 ml of an aqueous solution of about 20 wt% mannitol and lyophilized. Thus obtained white lyophilisate was pulverized in a small-sized ball mill at low room temperature for 30 hours to give a white powder of uniform particle size. The surface activity of this powder was measured and the result is shown in Table 2. The dispersibility of this substance on the water surface was very good.

Claims: 1. An artificial lung surfactant which is free of protein and comprises: (a) from 80 to 95% by weight of the whole composition of a mixture of (i) and a phosphadityl choline of the formula (I) and (ii) at least one of a cardiolipin of the formula (II) and a phosphadityl glycerol of the formula (III) wherein R₁, R₂, R′₁, R′₂, R′₃, R′₄, R″₁ and R″₂ are straight chain fatty acid acyloxy radicals having 14 to 25 carbon atoms and M is a cation; (b) from 5 to 20% by weight of the whole composition of a neutral lipid having straight chain saturated fatty acid acyloxy radicals having 14 to 25 carbon atoms; and (c) from 0 to 10% by weight of the whole composition of a straight chain fatty acid having 14 to 25 carbon atoms. 2. The artificial surfactant of Claim 1 which contains by weight of the whole composition, 55 to 80% of phosphatidyl choline and 10 to 35% of phosphatidyl glycerol and 5 to 20% of neutral lipids. 3. The artificial lung surfactant of Claim 1 or Claim 2, wherein the neutral lipid comprises predominantly a triglyceride. 4. A composition for treating respiratory distress syndrome comprising the artificial lung surfactant of any one of Claims 1 to 3 as its active principle. 5. The composition of Claim 4, wherein the artificial lung surfactant is dispersed in water or an aqueous electrolyte solution such as a saline solution. 6. The composition of Claim 4 or Claim 5, further comprising from 2 to 50 parts by weight of a medically-permissible, water-soluble powdery substance for each part by weight of the artificial lung surfactant. 7. The composition of Claim 6, wherein the powdery substance is an amino acid, a saccharide or a mixture thereof.

Inventors: KOBAYASHI, TSUTOMU, KOKUBO, MASAYUKI, TAKADA, YOSHINORI, YOSHIDA, TSUNEMASA
Applicants: TEIJIN LIMITED
Application year: 1983
Main classification: A61K31
IPC codes: A61K31