United States Patent Ofi1ice
`
`3, 1 on,20;2
`Patented Aug. 6, 1963
`
`1
`
`3,100,202
`PROCESS FOR PREPARING AN IRON HYDROXIDE
`POLY.iSOMALTOSE COMPLEX AND THE RE·
`SULTING PRODUCT
`Artlm:r Miille:r, §t. Geo.rgenstr. lOOJR, and Thecdo:r Bern-in,
`Ludwigstr. 19, both of §an.kt Gallen, Switze:rfaml
`· No Drawing. Flied J"nne 17, 1960, §er. No. 36,734
`10 Claims.
`(Ct 2611-209)
`
`The present invention relates :to an improved ther<a(cid:173)
`peutic composition containing iron and more particularly
`to the process of manufacture of a colloidal iron-poly(cid:173)
`isomaltose complex which is parenterally injectible.
`It is well known that hemoglobin, cytochrome, catalase
`and other prophyrine protein complexes containing iron
`cannot be synthesized by the body tissue unless iron is
`available from an outside source. Blood cells and other
`structures containing <iron are constantly destroyed in the
`normal processes of cell metabolism thus :liberating inor(cid:173)
`ganic iron which is in part excreted and has to be re(cid:173)
`placed. While most individuals maintain the requisite
`iron levels through normal food !intake, many individuals
`suffer from anemia brought 'abolllt by iron deficiency,
`thus requiring supplemental iron above that in :the food
`intake.
`It is recognized that ferrous sulfate, cM"bonate, citrate,
`soluble double salts and even metallic iron powder, to
`mention a few, have been and are now being used for
`oral iron therapy. It has been found, however, that such
`iron containing compounds, orally given, are incompletely
`absorbed and the metabolism of such is slow in many
`cases. Further, in some cases imn compounds when
`orally taken !results in severe alimentary disturbances.
`To overcome the obvious defects of the oral administra(cid:173)
`<tion iron containing compounds, saccharated iron oxide
`preparations have been used for intravenous injection with
`limited success, in all probability for fae reason that suc(cid:173)
`cessive batches vary in potency. Additionally, these prep(cid:173)
`arations are not suitable for intramuscular ur subcutane(cid:173)
`ous injection in that ,the high osmotic pressure 'and the
`possible alkalinity of the intravenous injectible prepara(cid:173)
`tions usuaHy result in considerable pain and inflamma(cid:173)
`tion at the site of the injection. Further, such prepara(cid:173)
`tions are not appreciably absorbed into the body when
`administered in this manner.
`A known treatment for iron defioiency anemia is a col(cid:173)
`loidal iron preparation prepared from the degradation
`products of dextran complexed with a solution ·or suspen(cid:173)
`sion of one or several trivalent iron compounds. Dextran
`or gum dextran, as it is sometimes called, is a polysac(cid:173)
`charide having the empirical formula (C6H 100 5)n and is
`obtained from the fermentation of a sucrose containing
`material, such as sugar cane, sugar beet, sorghum, molas(cid:173)
`ses 'and the like. It is preferably fermented under care(cid:173)
`fully controlled conditions by means of bacterium such
`as Leuconostoc mesenteroides, syn. Betacoccus arabi(cid:173)
`nosaceous (Cienkowski van Tieghem), Bergey's Manual
`of Determinative Bacteriology, fifth edition. The product
`of such a fermentation is called dextran and is a viscous
`mucilaginous substance with high molecular weight often
`reaching 200,000. Because of its high molecular weight,
`dextran is not directly suitable for injection, but is gen(cid:173)
`erally first hydrolyzed with a dilute mineral acid, filtered
`
`2
`and fractionated to recover simple polymeric forms of
`molecular weight of 30,000 to 80,000 or lower.
`The known colloidal iron dextron complexes have been
`produced by m1n1erous methods, for example by rnacting
`5 dextran degradation products in solution or suspension
`with ferric hydroxide or other trivalent iron salts and
`an excess of alkali. Other methods employed have been
`to react dextran with divalent iron salt to form ferrous
`hydroxide dextran complex which are subsequently con-
`10 verted by oxidation into the corresponding ferric hy(cid:173)
`droxide complex. Complexes prepared by known meth(cid:173)
`ods comprise up '1o about 27% by weight of Fe; however,
`more generally in the Tange of 16% to 25% and ru-e char(cid:173)
`acterized by having a rntio of one mol of Fe to each an-
`15 hydroglucose unit of the dextran. Heretofore attempts to
`increase the iron to anhydroglucose ratio have been un(cid:173)
`successful.
`In accordance whh ·the process of ·this invention, we
`produce a parenteraHy injectible iron hydroxide poly-
`20 isomaltose complex which contains 32% Fe by weight
`and has a ratio of 2 mols Fe to each anhydroglucose unit
`-0f ·the polyisomaltose.
`The iron hydroxide polyisomaltose complex prepared
`in accordance ·with our process provides a therapeutic
`25 preparation whlch is more heterogeneous in particle size,
`surprisingly lower toxicity, better pharmacological prop(cid:173)
`erties and of higher therapeutic efficacy than the iron(cid:173)
`fo addition to rthe
`dextran complexes hitherto known.
`foregoing advantages, we have discovered that both tri-
`30 valent and divalent iron salts may be utilized successfully
`in the process of this invention.
`It has been theorized that ·the therapeutic advantages
`derived from a ferric hydroxide polyisomaltose complex
`prepared in accordance with our process is due •to <the ratio
`35 of two mols of iron .to each ruihydrog1ucose unit of the
`polyisomaltose; however, while this theory has been ad(cid:173)
`vanced as a possible explanation of the advantages de(cid:173)
`rived from our invention, the invention is not limited to
`any particular theory or theories.
`The "iron polyisomaltose" of our invention is a com(cid:173)
`plex compound consisting of iron hydroxide and poly(cid:173)
`asomaltose. Polyisomaltose is a polyhexosan; in other
`words, a polydisaccharide made up of glucose units
`45 (CsHHP5)n. For analogy to the nomenclature in Chemi(cid:173)
`cal Abstracts
`(e.g., polyhexosan-? glucos·an-?dextran-7
`polyisomaltose), the compound could be designated
`"polyisomaltose ferric hydroxide." While "polyisomal(cid:173)
`!f:ose" is a term used foosely for "dextran" as mentioned
`50 hereinbefore, the latter is a compound of very high mo(cid:173)
`lecular weight, whereas polyisomaltose is a degradation
`product of dextran consisting of polymerized glucose resi(cid:173)
`dues joined predominantly by 1,6 linkages.
`The molecular range of the partially depolymerized
`55 dextran used as a starting material is selected from· the
`standpoint of its mtrinsic viscosity. It is known that the
`term intrinsic viscosity refers to the limiting value of
`specific viscosity divided by concentration at infinite di(cid:173)
`lution measmed as follows: 'Ilhe "flow time" of solutions
`60 of different concentrations is determined by a viscometer.
`T'ne flow time of ,the solution divided by the flow time
`for water at the same. temperature gives the relative vis(cid:173)
`cosity of llhe dextran solution at a given concentration.
`The specific viscosity of the dextran solution at a given
`
`40
`
`Pharmacosmos, Exh. 1031, p. 1
`
`

`

`3,100,202
`
`3
`concentration is obtained by subtracting 1.0 from the
`value for relative ·viscosity. The specific viscosity of
`each solution is divided by the concentration of that
`solution and the results are plotted against the percentage
`concentration of the solution from which it is obtained.
`By extrapolating the 1graph obtained to zero concentra(cid:173)
`tion, the limiting value of the specific viscosity divided
`by .1Jhe concentration is obtained. This limiting value
`is the intrinsic viscosity of the material in solution.
`In accordance iw:ith the process of this favention, a
`solution or suspension of dextran containing predomi(cid:173)
`nantly 1,6 glucose linkage !is mixed with an acidic solu(cid:173)
`tion of an iron com.pound, in respective amounts of about
`48 to 141 weight parts of said iron com.pound per 100
`parts of dextran. While it is advantageous to use as a 15
`starting material a dextran having a maximum intrinsic
`viscosity at 25° C. of 0.1, dextran of hi·gher intrinsic
`viscosity may .be utiHzed; however, where such is used,
`1Jhe acidic solution of the iron compound and dextran
`is heated until the intriinsic viscosity of the <lextran is
`a maximum of 0.1 and without isolating the depolym(cid:173)
`erization products the process is continued. An alkali
`carbonate solution is added to the polyisomaltose-iron
`solution until precipitates formed dissolve with vigorous
`stirring. The initial solution is ochre colored which upon
`completion of the reaction turns brown-red in color.
`.All of the carbon dioxide formed during >this reaction
`will have evolved when the reaction is complete.
`.An
`alkali hydroxide is then added to the solution until the
`formed suspension is wen on the alkaline side and then
`heated until all suspended iron hydroxide particles are
`in solution.
`The alkaline ferric hydroxide polyisomaltose complex
`containing solution may be neutralized prior to being
`isolated and purme<l. As neutralization reagents, solid,
`liquid or gaseous acids may be used, for example cation
`exchange .resins in the H-form, fuming sulfuric acid and
`hydrochloric add. In order to free 1Jhe solution of elec(cid:173)
`trolytes an alkaline anion exchange resin may be added
`in addition to ·the .cation exchange resin, or the solution
`may be dialyzed against .water.
`Where a divalent iron salt is used initially, the alkaline
`ferrous !hydroxide polyisomaltose solution is dialyzed
`against well aired, flowing and demineralized water which
`dialysis converts the divalent iron hydroxide to the tri(cid:173)
`valent form while effecting neutralization and removal
`of electrolytes .
`.As iron salts, :there may be employed any water solu-
`ble salt sucih as ferric or ferrous chloride, nitrate, acetate,
`sulfate and the like. Suitable alkaHes im:fode alkali metal
`hydroxides, ammonium hydroxide ·and the like. Suitable
`carbonates include sodium and potassium carbonates and
`bicarbonates.
`It is clear that any iwater soluble alkali
`and carbonate may be used with success in the process
`of this invention, the alkali and carbonate chosen being
`dictated only by the economics of the process.
`Excellent water soluble preparations of our compound
`are obtained by any of the well~known processes for
`example by evaporation of the neutral solutions under
`reduced pressure or by precipitation with a water solu(cid:173)
`ble organic solvent for example methyl or elihyl alcohol.
`The following examples set out in detail are illustra(cid:173)
`tive of the process of this invention:
`
`4
`NaOH was added. The mixture was maintained at a
`temperature of 70° C. for 30 minutes after which 1Jhe
`solution was cooled and the pH adjusted to 6.2 with
`90 ml. of a strongly acidic cation exchange >resin and
`5 20 ml. of an alkaline ex-change resin. The adjusted
`solution was filtered from the exchange resins and mixed
`with 96% ethyl alcohol in a ratio of one part by volume
`solution to 2.5 parts by volume of alcohol. The pre(cid:173)
`cipitated ferric hydroxide polyisomaltose complex was
`10 separated from the supernatant solution and dried ·under
`vacuum. The analytically pure complex contained 32%
`iron. The complex was processed into an ·isotonic aque(cid:173)
`ous solution containing 5 % iron.
`Example 2
`35 g. of dextran having an intrinsic viscosity at 25° C.
`of 0.05 was dissolved in 75 ml. of water with heat. The
`solution was cooled .and to the cooled solution, 50 g.
`FeS0'1·7H20 was added and dissolved. To this solu(cid:173)
`tion an additional 75 ml. of water was added. Na2C03
`20 l\¥as added to .the solution until a pH of 2.3 was reached.
`After all of the carbon dioxide formed had evolved, 11
`ml. of 10 N NaOH was added and the ;reaction was
`allowed to proceed for 30 minutes at a temperature of
`65 ° C. The solution was cooled, centrifuged and di-
`25 alyzed against well-aired, flowing and demineralized
`water until there was neutral reaction and no trace of
`sulfate ions. The ferric hydroxide polyisomaltose solu(cid:173)
`tion was evaporated under reduced pressure at a tem(cid:173)
`perature of 40° C. until it ihad an iron content of 5%.
`30 The solution was made isotonic by ,the addition of NaCl.
`The analytically pure complex contained 32% iron.
`The ferric hydroxide polyisomaltose compound 'Pre(cid:173)
`pared in each of the foregoing examples was analyzed by
`35 fractionally precipitating the complex from aqueous solu(cid:173)
`tion with methanol to a constant iron content.
`rrhe re(cid:173)
`sults showed in all fractions a ratio of 2 mols of iron for
`each anhydroglucose unit of the polyisomaltose.
`The invention has been described in the foregoing but it
`40 will be ·understood that many variations may be introduced
`in details of procedure and conditions without departure
`from the scope of the invention and we intend to be limited
`only by the following claims.
`We claim:
`1. .A process of preparing an iron hydroxide poly-
`45 isomaltose complex containing about 32% iron by weight
`comprising heating an acidic aqueous solution of a water(cid:173)
`soluble dextran, havi.mg an intrinsic viscosity greater than
`0.1 at 25° C. and a water-soluble iron compound in !re(cid:173)
`spective amounts of about 48 to about 141 weight paJJts
`50 of said iron compound per 100 weight parts of dextran
`until the intrinsic 'Viscosity of said solution is not more
`than 0.1 at 25° C., reacting the resulting solution with an
`alkali carbonate at ·an acid pH whereupon carbon dioxide
`is evolved, alkalinizin.g the resulting soiution with an
`55 alkali metal hydroxide ·after completion of the carbon
`dioxide evolution, and thereafter heating the resuiting
`solution to form said complex.
`2 . .A process of preparing an iron hydroxide polyiso(cid:173)
`maltose complex containing about 32% iron by weight
`60 comprising reacting an acidic aqueous solution of a water
`soluble dextran having an intrinsic viscosity of not more
`than 0.1 at 25° C. and a water soluble iron compound
`in respective amounts of about 48 to about 141 weiight
`parts of said iron compound :per 100 weight parts. of
`65 dextran with an alkali carbonate at an acid pH whereupon
`carbon dioxide is evolved, alkalinizing the resulting solu(cid:173)
`tion with an alkali metal hydroxide after said carbon di(cid:173)
`oxide has evolved, and thereafter heating the resulting
`solution to form said -complex.
`3. The process as claimed in claim 2 wherein said iron
`compound contains trivalent iron.
`4. The process as claimed in claim 2 wherein said iron
`compound contains divalent iron.
`5. The process as claimed in claim 2 wherein said alkali
`carbonate is sodium carbonate.
`
`70
`
`Example 1
`A mixture of 50 g. polyisomaltose having an intrinsic
`viscosity of 0.30 at 25" C., 412 ml. water, 80 ml. of
`an aqueous solution containing 30% by weight
`FeC13 ·6H20
`and 8.32 ml. of 37% HOl was boiled under >reflux until
`the intrinsic viscosity at 25° C. decreased to 0.06. The
`solution was cooled and Na2C03 was added to the solu(cid:173)
`tion until the pH reached about 2.4.
`.After all of the
`carbon. dioxide formed had evolved, 45 ml. of 10 N 75
`
`Pharmacosmos, Exh. 1031, p. 2
`
`

`

`3,i00,202
`
`6. The process as claimed in claim 2 wherein said alkali
`metal hydroxide is sodium hydroxide.
`7. The process as daimed in claim 2 wherein the pH
`of said solution after reaction with alkali carbonate is
`about 2.3 and the pH of said solution after alkalinization 5
`with alkali metal hydroxide is not less than 11.
`8. An iron hydroxide polyisomaltose complex contain(cid:173)
`ing about 32 % iron by weight.
`9. A ferric hydroxide polyisomaltose complex contain(cid:173)
`ing about 32% iron 'by weight.
`10. A :ferrous hydroxide polyisomaltose complex con(cid:173)
`taining about 32% iron by weight.
`
`6
`References Cited in the file of this patent
`UNITED STATES PATENTS
`London et al. ------------ Jan. 21, 1958
`Herb ------------------ May 5, 1959
`Floramo --------------- Feb. 20, 19'62
`
`2,820,740
`2,885,393
`3,022,221
`
`OTHER REFERENCES
`The New England Journal of Medicine, vol. 260, Jan.
`IO 22, 1959, paige 180.
`Drug Trade News, vol. 35, No. 10, May 16, 1960,
`pages 1 and 72.
`
`Pharmacosmos, Exh. 1031, p. 3
`
`