2,407,412 Patented Sept. 10, 1946 . UNITED STATES PATENT OFFICE 2,401,412 ’ mum-zone SOLUTIONS Douglas V. Frost, Waukegan, 111., assignor to Ab bott Laboratories, North Chicago, Ill.,- a corpo ration of Illinois No Drawing. Application August 15, 1942, Serial No. 454,919 10 Claims. (01. 167-81) 1 '2 The present invention relates to improved I therapeutic solutions and more particularly to stabilized ribo?avin-nicotinamide solutions. The 7 Per cent w/v Ribo?avin _____________________________ __ 0.10 preserlilt application is a congnuiiéignéiln-part of \ my p or application Serial 0. ,8 . Ribo?avin is a naturally occurring representative of the polyhydyoxyisoauoxazine vitamins and Nicotinamide __________________________ __ 5.00 5 . c 'lll'he 320v;a?grg‘ggné?eagi?ggdwggegh?? sglustign i: comgllete. The solution is then cooled its de?ciency 1s wldespread' Clinical symptoms of _ polyhydroxyisoalloxazine de?ciency include and su?lcient acidic material, such as hydrochlo no acid added to adjust the pH to about 45 keratitis, cheilosis, vmydriasls, photophobia, etc. 10 to 66 ’ :' Ribo?avin is only very slightly soluble in water ' ' ' and hypodermical administration in this form 11 necessitates the use of large volumes of liquid. The natural solubility of ribo?avin in pure water , Ribo?avin Per cent w/V ___ 0.10 at 20' C., for example, is only about 0.013 per 15 Nicotinamidev ___________ -._. _____________ __ 5.00 cent and the administration of a good therapeu- Thiamine hydrochloride _________________ __ 0.50 tic dose (10 mg.) at this temperature necessitates the injection of about 78 cc‘ 9f solution‘ The above ingredients are mixed with about 80 per cent‘ of the total volume of water required In my co'pending related apphcati?“ Serial in the formula and solution induced by warming. No’ 416’757' which hats issued as Patent No‘ 20 When solution is complete the resulting solution 2’3.8§’261’.I ha"? descnbed 8' mephod for 50m‘ is allowed to cool and su?icient acidic material bilizing ribo?avin by the formation of a ribo- such ?avin-boron complex. These boron compositions added to adjust the pH to about 4 to 5_0_ The as monosodium dihydrogen phosphate’ haw? proven highly Sa?SfF‘Ct-QW as .the-y employ ?nal solution is then made up by addition of “.lmlmum .amounts of imectmn mm? and pro’ 25 chemically pure water. In certain cases, for ex ¥i1gg?ap€?tigald giggsu?gia?ggtgdgggggfm?on of. p . ample. when preparing compositions containing thiamm for oral administration the use of a pH During the research work carried out on th1s of 25 to 4 is preferred. investigation I also discovered that nicotinamide The present invention is not limited to the and water soluble saltsof nicotinlc acid solubil- 30 above examples_ For example’ in place of the ized polyhydroxyisoalloxazines Such as ribo?avinacidic materials described above other acidic buf With continued investigation. including assay fers which are not objectional for parenteral in tests running over relatively long periods of time jection, such as phosphoric acid, and the like I discovered that these compositions possessed may be used. In addition to thiamin, other vita the desired physical stability but lacked the es- 35 mins, such as pyridoxine and salts of pantothenic sential chemical. or physiological stability. Exacid, may also be added as desired. The follow tensive tests, for example, showed ribo?avining example is illustrative nicotinamide or -sodium nicotinate solutions to be unsatisfactory for use after standing for sev- m Per cent w/v eral weeks or months due to loss in vitamin po- 40 Ribo?avin _____________________________ __ tency. . Nicotinamide __________________________ __ 0,3 10.0 The principal object of the present invention is Thiamin hydrochloride _________ _-»_ _____ __ 1.0 , to provide polyhydroxyisoalloxazine and partic- Pyridoxine hydrochloride ________________ __ 0.1 ularly ribo?avin solutions of desired concentra- 45 Calcium pantoihenate ------ 4- ---------- -_ 1.0 tions characterized by both physical and physio- Boric "Md 0-5 ‘logical stability. Other objects will be apparent as the detailed The ribo?avin, nicotinamide and acid ingre dients of this example are preferably ?rst mixed description hereinafter proceeds. 1 _ -—- - - together in about 80 cc. of water and solution I have discovered that ribo?avin-nicotinamide 50 induced by warming. After solution the other solutions may be physiologically stabilized by ad- . ‘ justing the pH value of the solutions to 2.6 to 6.6, and preferably from about 4 to 6.6. The fol- » lowing examples will serve to illustrate the pres- _ ent invention. ' ingredients are added and the resulting solution then made up to 100 c0- by addition of distilled Water- In this example. which has a pH of about 4-5. the ratio is 033% ribo?avin t0 1.0% 55 nicotinamide. This represents a 50% increase 2,407,412 4 in ribo?avin over the ribo?avin-nicotinamide ratio in Examples ‘1 and II. Increase in ribo ?avin was found possible by the discovery that the other vitamin ingredients used in this ex ample are characterized by valuable. additive ribo?avin solubilizing effects. The solubilizing action of boric acid is also effective in Example . salt formed between molecular. equivalents of nicotinamide and hydrochloric acid, has 9. DH of 2.0 and ‘has a low solubilizing capacity for ribo?avin. Thus while the pH range which can be used to obtain physiological stability is 2.6 6.6, the range which can be used to the greatest advantage from the standpoint of both physi ological and physical stability (high solubility) falls roughly between pH 4 and pH 6.6. The acidic solutions of the present invention contain the ribo?avin in desired concentrations and of utmost importance retain their physio concentrations. I discovered, for example, that logical potency over long periods of time. In while 5 per cent nicotinamide solubilized 0.1 per order to retain therapeutic potency in the present cent ribo?avin at pH 5.0, 10 per cent nicotinamide solubilized 0.28 per cent ribo?avin at pH 5 in 15 compositions the acidic material should be sum cient tolower the pH not only below the alkaline stead of 0.2 per cent as reported in early in limit but also below the neutral point or pH ‘l’. vestigations. I also discovered that 20 per cent, 30 Any acidic material which is substantially non per cent, 40 per cent and 50 per cent nicotinamide toxic at the concentration employed may be at pH 5 solubilized about 0.6 per cent, 1 per cent, 1.6 per cent and 2.5 per cent ribo?avin, respec 20 used. Tests show that alkaline ribo?avin nicotin tively. These discoveries were unexpected for amide solutions lose from about 33 to 100 per early investigations with relatively low concentra III. . During the research investigation in this ?eld, I discovered that nicotinamide possessed unique solubilizing effects when used in relatively high tions of nicotinamide, i. e., up to 10 per cent as cent of their ribo?avin potency on standing for several months to a year at room temperatures. illustrated above, had indicated that doubling the percentage of nicotinamide merely doubled 25 Tests also show that neutral solutions lose from about 15 to 30 per cent of their potency under the percentage of dissolved ribo?avin. However, similar conditions. While solutions of this lat ter type having a pH of 'l or slightly below come within. the range of usable compositions, experi increased about 2.6, 6, l0, l6 and 25 times by using 2, e, 6, 8 and 10 times, respectively, the 30 ments have demonstrated that such solutions must be used shortly after preparation or, if initial amount, i. e. 5 per cent, of nicotinamide. stored, must be kept at refrigerated temperatures The following example will serve to further il in order to maintain the desired pharmaceutical lustrate the present invention. the above ?gures (which are given as % w/v) show that the amount of ribo?avin solubilized is stability. , The acidic solutions of the present invention Per cent w/v 35 make it unnecessary to use the solutions within Ribo?avin ___ 0.6 a relatively short time after preparation and also Nicotinamide 20.0 make it unnecessary to keep the solutions under The above ingredients are dissolved with heat carefully controlled temperature conditions, i. e. ing in water in the usual manner. When solu 40 below room temperature. In addition, as the tion is complete about 0.2 per cent of a concen acidic solutions are substantially free from physi trated solution of hydrochloric acid is added to ological deterioration, the present invention bring the pH of the final solution to about 5.0. makes it unnecessary in ordinary commercial If desired, about 0.5 per cent boric acid may be practice to run frequent ‘biological rechecks for added as this ingredient in addition to its solu such deterioration. bilizing e?ects, has also been found to be an The ribo?avin compositions solubilized by nico excellent physiologically inert bacteriostatic agent tinic acid salts are not stable under the 2.6-6.6 for use in the therapeutic solutions of the present pH range employed in the above nicotinamide invention. ' solutions. The solutions employing salts, such as After discovering the importanceof pH control the sodium, monoethanolamine, methyl gluca in ribo?avin-nicotinamide solutions with regard mine, etc. nicotinates must be maintained at a to the physiological stability of ribo?avin, I made pH of about 6 to 6.6. the further discovery that pH control in the acid It will !be understood that the present invention pH range is essential to control of solubility or is not limited to the above illustrative examples. physical stability. For instance 5 per cent 55 All modi?cations of the present invention are in» nicotinamide will solubilize about 0.1, per cent tended to be covered by the following claims. ribo?avin at about pH 4.3 and above, but as I claim: ' the pH is lowered by addition of acid a progres 1. A therapeutic composition comprising an sive decrease in ribo?avin solubility occurs. acidic aqueous solution containing at least about Thus at about pH 4.05, 3.6, 3.2, 3.0 and 2.5, 5 60 1 mg. of ribo?avin per cc. and at least about 50 per cent nicotinamide will solubilize about 0.095 mg. of nicotinamide per cc. and a small amount per cent, 0.07 per cent, 0.056 per cent, 0.044 per of acidic material su?icient to maintain said so cent and 0.032 per cent ribo?avin, respectively. _ lutionvat a pH of 4 to 6.6. Likewise, solutions of 10 per cent, 20 per cent 2. ,A therapeutic solution comprising an acidic and 30 per cent nicotinamide were found to have ~ ‘aqueous solution containing more than 0.2 per decreasing capacity to solubilize ribo?avin as the cent ribo?avin and more than 10 per cent nico pH was lowered below about DH 5. The decrease tinamide, said solution having a pH of 4-6.6. in solubilizing capacity of nicotinamide for ribo 3. Therapeutic compositions comprising acidic ?avin with decrease in pH is apparently related aqueous solutions containing percentages of ribo to salt formation between electropositive nicotin ?avin ranging from 0.2 per cent to 2.5 per cent amide and electronegative acid anions. This ap 70 and nicotinamide ranging from 10 per cent to 50 percent respectively, said solutions having a pH pears likely because the pH curve of electrometric of 4-6.6. ' titration of nicotinamide follows the ribo?avin solubility curve closely. For example, a 10 per 5.5;The process of stabilizing an aqueous ribo cent solution of'nicotinamide hydrochloride, the 75 ?avin-"nicotinamide solution which comprises ad 2,407,412 5 . justing the pH of the solution by means of acidic and stable for a time period of a year or so com material to a value of about 4 to 6.6. prising an aqueous solution containing ribo?avin in excess of 0.013%; said solution containing also nicotinamide to solubilize the ribo?avin; and su?icient hydrochloric acid to adjust and main tain the pH of the solution at values between 2.6 5. A stable therapeutic preparation compris ing an aqueous solution having a pH of 4-6.6 and containing ribo?avin and a solubilizing agent consisting of nicotinamide. the nicotinamide be ing present in amounts between 10% and 50%; .the ribo?avin present being not. less than 2% of the nicotinamide present. 6. A stable therapeutic preparation comprising 10 and 6.6. _ 9. A therapeutic ‘composition for parenteral use and stable for a time period of a year or so com prising an aqueous solution containing ribo?avin in excess of 0.013%; said solution containing also nicotinamide to solubilize the ribo?avin; and su?icient monosodium dihydrogemphosphate to adjust and maintain the pH of the solution at ing present in amounts between 30% and 50%; the ribo?avin present being not less than 3.8% of 15 values between 2.6 and 6.6. 10. The process of stabilizing an aqueous ribo the nicotinamide present. ?avin solution to prevent decomposition over a '7. A therapeutic composition for parenteral use an aqueous solution having a pH 01', 4-6.6 and containing ribo?avin and a solubilizing agent consisting of nicotinamide, the nicotinamide be time period of a year or so, and to retain ‘the and stable for a time period of a, year or so com ribo?avin in solution for the same period, which prising an aqueous solution containing ribo?avin in excess of 0.013%; said solution containing also 20 comprises: adding nicotinamide to prevent pre nicotinamide to solubilize the ribo?avin; and su?‘lcient acidic material to adjust and maintain the pH of the solution at values between 2.6 and 6.6. cipitation; and preventing decomposition by the addition of su?icient acidic material to maintain the pH at about 4.5. a .8. A therapeutic composition for parenteral use 25 DOUGLAS V. FROST.