IE43086B1 - Stable radiographic scannin agents - Google Patents

Abstract

A radiographic indicator based on technetium-99m is prepared by dissolving ascorbic acid or a pharmacologically acceptable salt or ester thereof together with a reducing agent for pertechnetate in a pertechnetate solution. The composition suitable for this purpose contains (I) a reducing agent for pertechnetate or a pertechnetate solution and (II) an amount, which suffices to stabilise the composition in the presence of oxygen and radiolysis products, of ascorbic acid in the form of the free acid or of a pharmacolgically acceptable salt or ester of the acid.

Description

This invention relates to a method of reparation of stable scintigraphic scanning agents employing 3chnetium-99m, and to compositions useful therein.

Scintigraphy and similar radiographic techniques re finding ever increasing application in biological and » sdical research and diagnostic procedures. In general, cintigraphy procedures involve the preparation of radioctive scanning agents which, upon introduction into a iological subject, become localized in specific organs, issue or skeletal material which are under study. When 3 localized, traces, plots or scintiphotos of the dissibution of the radioactive material may be made by irious radiation detectors, such as traversing manners or scintillation cameras. The :sultant distribution and corresponding relative in;nsities may then be used to indicate the position :cupied by the tissue in which the medium is localized as 3086 well as indicate the presence of abberation, pathological conditions or the like.

Recently developed scintigraphic organ and skeletal 0 9m scanning agents have employed technetium-99m ( Tc) as a QQm radionuclide source. Technetium-09m is obtained as a mTc solution in the pertechnetate (99mTcO4~) oxidation state from commercial generators by eluting them with an isotonic saline solution. One commercial generator presently available to produce a pertechnetate solution is distributed by the E. R. Squibb Company and sold under -the trademark Technetope HiCon. Also, methyl ethyl ketone extracted pertechnetate in isotonic saline is presently available from New England Nuclear of Boston, Massachusetts, under the designation Instant Technetium. in general, 99mTc labelled scanning agents are prepared by combining a pertechnetate-99m isotonic saline solution with a pertechnetate reducing agent such as the stannous, ferrous or chromous salt of sulfuric or hydrochloric acid.

For example, Yano, et al. in the Journal of Nuclear Medicine.

Vol. 14, No. 2 at pages 73-8, and Subramanian, et al. in the Journal of Nuclear Medicine, Vol. 13, No. 12 at pages 99m 947-9, describe Tc skeletal scanning agents prepared by mixing a pertechnetate solution with an aqueous solution of a stannous phosphonate reducing agent and distannous-ethane-l-hydroxy-1,l-diphosphonate.

While such procedures provide scanning agents which are superior to those previously available, they have short-comings; most notably, it has been found that 3086 conventional technetium-containing scintigraphic scanning agents are unstable in the presence of oxygen and radiolysis products. Accordingly, previously-described technetium-based scanning agents have been made' oxygenfree by saturating the composition with oxygen-free nitrogen gas or by preparing the agent in an oxygen-free atmosphere or in a vacuum. However, even such painstaking precautionary procedures are not entirely satisfactory, since it is extremely difficult to maintain oxygen-free conditions. For instance, pertechnetate solutions may contain dissolved oxygen which, if not detected prior to combination with the pertechnetate reducing agent, forms a product which is unstable and results in the production of free pertechnetate-99m.

The present invention provides a method Of preparation of technetium-9 9m based scintigraphic scanning agents. The compositions used in the process of ( the present invention comprise a pertechnetate reducing agent or oxidized pertechnetate solution and an effective amount, sufficient to stabilize said compositions in the presence of oxygen and radiolysis products, of ascorbic acid or the pharmaceutically acceptable salts or esters thereof.

In its method aspects the present invention provides an improved method of preparing a technetium-99m based scanning agent comprising codissolving no more than 1% by weight of the solution of 'ascorbic acid or a pharmaceutically acceptable salt or ester thereof and a pertechnetate reducing agent in an oxidized pertechnetate solution. - 4 43086 This invention is based on the discovery that ascorbic acid and its pharmaceutically acceptable salts and esters can be utilized to prepare uniquely stable I technetium-99m-based scintigraphic scanning agents. « · 99m As previously mentioned, Tc labelled scanning agents are prepared by mixing a pertechnetate solution with a pertechnetate reducing agent. It has been found that small amounts of ascorbic acid, its salts or esters, can be combined with either the pertechnetate solu10 tion or the pertechnetate reducing agent prior to their admixture thereby providing compositions uniquely suited for the preparation of superior ^mTc scanning agents. Accordingly, there are two compositional aspects to the present invention. In one aspect, compositions of the presi5 ent invention comprise a pertechnetate reducing agent containing a pertechnetate reducing ion and no more than 25%, preferably no more than 10%, by weight, of ascorbic acid or a pharmaceutically acceptable salt or ester thereof. In a second aspect, compositions of the present invention comprise an oxidized pertechnetate solution having dissolved therein no more than 0.10%, preferably no more than about 0.05%, by weight, of ascorbic acid or a pharmaceutically acceptable salt or ester thereof.

As noted above the present invention encompasses two compositional forms. For purposes of the present invention, it is not critical which compositional form is used to prepare the final technetium-based scanning 1086 agent. Commercial producers of pertechnetate solution may find it desirable to dissolve low levels o.f an ascorbic acid compound (as used hereinafter the term “an ascorbic acid compound is intended to include ascorbic acid and its pharmaceutically acceptable salts and esters) directly into the pertechnetate solution as it is eluted from the generator, or to incorporate an ascorbic acid compound directly on the generator column. Others may find it more convenient to combine the ascorbic acid compound with a pertechnetate reducing agent. In either case upon combining the pertechnetate solution with the reducing agent, an improved highly stable scanning agent is provided.

Ascorbic acid, the most preferred compound of the present invention, Occurs naturally in a wide variety of plant and animal species. Particularly good sources include citrus fruits, aerola (the ripe fruit of Malplghla punicifolia L., or West Indian Cherry), and fresh tea leaves. Ascorbic acid can be synthesized by the acid-catalyzed oxidation of-L-sorbose.

The pharmaceutically acceptable salts and esters of ascorbic acid can be prepared by standard well-known neutralization and esterification procedures. A thorough discussion of suitable procedures for preparing ascorbic acid salts and esters can be found in The Chemistry of Organic Compounds, Third; Noller (Ed.) 1966.

In general, the pharmaceutically acceptable salts of ascorbic acid can be prepared by acid-base neutralization using one equivalent of a selected base. Similarly, the pharmaceutically acceptable esters of ascorbic acid can be prepared by reacting equimolar amounts of.the acid with selected alcohols.

In practice, the salts and esters of ascorbic acid suitable for use in the present invention can be selected for use according to their solubility in a pertechnetate solution. It is, of course, preferable that the salts and esters of ascorbic acid be readily soluble in a pertechnetate solution. Accordingly, suitable ascorbic acid salts include the alkali metal, alkaline earth metal, heavy metal and ammonium salts. The alkali metal salts such as sodium, potassium and lithium salts of ascorbic acid are readily soluble and accordingly preferred for use herein. Various ascorbic acid ammonium salts, wherein the cation is N(R')^ are also suitable for use .-. 7 _ herein. These include, for example, alkylammoniura, alkanolammonium arid arylammonium salts of ascorbic acid.

It is of course understood that the solubility of ammonium salts is largely dependent upon the number and nature of the substituent groups on the nitrogen atoin. In general, and as used herein, preferred readily soluble ammonium salts include those wherein each S.' is either hydrogen or to about Cg hydrocarbyl. Monlimiting examples of pharmaceutically acceptable ammonium salts of ascorbic acid useful herein include the ammonium, methylammonium, dimethylammonium, tetramethylammonium, bis-(tetramethylammonium), 2-hydroxypropylammonium, bis-(2-hydroxypropylammonium), ethanolammonium, diethanolammonium, triethanolammonium, bis-(triethanolammonium) , phenylammonium, naphthylammonium and quinolylammonium salts.

The alkaline earth metal salts, for example the calcium and magnesium salts, although less soluble, are * ? also suitable for use herein.

The heavy metal salts, for example the iron and tin salts, are also suitable for use herein.

The pharmaceutically acceptable esters of ascorbic acid, readily soluble in pertechnetate solutions, include, for example, the to Cg lower alkyl esters such as the methyl, ethyl', propyl, isopropyl, butyl, isobutyl and pentyl·esters of ascorbic acid.

In embodiments of this invention in which the ascorbic acid compound is combined with the pertechnetate reducing agent, the choice of reducing agent is not critical As used herein the term pertechnetate reducing agent is intended to include compounds, complexes or the like comprising a reducing ion capable of reducing heptavalent technetium to tetravalent and/or pentavalent technetium.

Suitable pertechnetate reducing agents may be combined with numerous adjuvants such as fillers and skeletal- or other organ-specific carriers. For example, skeletal scanning agents have been prepared utilizing metallic salts of sulfuric and hydrochloric acid such as stannous chloride, chromous chloride and ferrous sulfate as the pertechnetate reducing agent in combination with various organic phosphonates and/or phosphates as the bone seeking carrier.

Lung and organ scanning agents have been prepared utilizing buffered solutions of a denatured microprotein having di15 valent tin bound thereto as the pertechnetate reducing agent. Other systems capable of reducing pertechnetate-99m include, for example, acid-thiosulfates, acid-hydrogensulfates, iron colloids, and acid-borohydrides. U.S. Patent Specifications Nos. 3,735,001 granted May 22, 1973; 3,863,004 granted January 28, 1975; 3,466,361 granted September 9, 1969; 3,720,761 granted March 13, 1973; 3,723,612 granted March 27, 1973; 3,725,295 granted April 3, 1973; 3,803,299 granted April 9, 1974; and 3,749,556 granted July 31, 1973 disclose various pertechnetate reducing agents comprising reducing ions capable of reducing heptavalent pertechnetate to tetravalent and/or pentavalent technetium-99m The concentration of ascorbic acid compound utilized in embodiments of this invention in which the ascorbic acid compound is combined with a reducing agent 308θ will vary depending upon the ultimate use of the composition and the concentration of inert or filler materials utilized. It has been found, however, that concentrations of the ascorbic acid compound greater than about 25% inter5 fere with the formation of an acceptable scanning agent and should be avoided. For most purposes concentrations in the range of about 0.1% to 5% are suitable Where it is desirable to incorporate the ascorbic acid compound directly into the pertechnetate solution, the I ascorbic acid compound can be simply dissolved either during or after elution of the pertechnetate generator. The elution process is thoroughly described in U.S. Patent Specification No. 3,369,121.

In embodiments of the present invention in which the ascorbic acid compound is dissolved in a pertechnetate solution, the concentration of ascorbic acid compound will vary depending upon the degree of saline dilution. It has been found that an ascorbic acid compound concentration greater than 0.1% interferes with the formation of 1 an acceptable scanning agent. Accordingly, a concentration no greater than 0.1%, preferably no greater than 0.05%, by weight, is used. A concentration within the range of from about 0.01% to about 0.001% is acceptable for many applications.

Suitable concentrations of ascorbic acid compound will vary somewhat depending upon pH conditions. 3086 In the method of the present invention the ascorbic acid compound and pertechnetate reducing agent may be either simultaneously dissolved or sequentially dissolved in the pertechnetate solution. Either co5 dissolving procedure results in an improved technetiumbased scanning agent.

In a preferred embodiment of the present invention, a stable technetium-based skeletal scanning agent can be formed by the direct addition of a pertechnetate solution to a composition comprising: a pertechnetate reducing agent containing a metallic reducing ion in salt form, such as stannous chloride; from about 0.3% to about 1.5%, by weight, of an ascorbic acid compound; and a skeletal-specific carrier compound selected from the mono-, di- or polyphosphonates. A broad range of mono-, di- and polyphosphonates are now known to concentrate on the skeleton upon injection 13086 of solutions thereof into a patient. Operable species for this purpose include mono-, di- and poiyphosphonates selected from the group consisting of: P03H2 wherein each R is hydrogen or CHjOH and n is an integer of from 3 to 10; p°3h2 II. po3h2 wherein is hydrogen, alkyl containing from 1 to about 20 carbon atoms, alkenyl containing from 2 to about 20 carbon atoms, aryl (e.g., phenyl, naphthyl), phenylethenyl, benzyl, halogen (e.g., chlorine, bromine and fluorine), hydroxyl, amino, substituted amino (e.g., dimethylamino, diethylamino, N-hydroxy-N-ethylamino, acetylamino), -CI^COOH, -CH2P03H2, CII(PO3I12) (Oil), or -[CH2C(PO3H2)2]-H where n = 1 to 15, and R2 is hydrogen, - 12 43086 lower alkyl (e.g., methyl, ethyl, propyl and butyl), amino, benzyl, halogen (e.g., chlorine, bromine, and fluorine), hydroxyl. -CH-COOH, -CH^PO^, or -CH2CH2PO3H2; ?°3H2 IX1· <CH2’n 1_ CH-OH P03H2 wherein n is an integer of from 3 to 9; J°3H2 R3-c-R3 IV.

/ \ X 3 : ho. p-c c'23 ι ι 32 r3 r3 wherein each R3 is hydrogen or lower alkyl (e.g., methyl, ethyl, propyl and butyl); V. |-c-po3h2 <CF2>n I-c-po3h2 - 13 43086 wherein n is VI. an integer of from 2 to 4; II OH-P-OH 0 I II C-0-P-OH I I OH-P-0-C I 1 OH-P-OH II VII.

COOH I c = I H COOH I : C P03h2 VIII.

H I H-CI Ο —P OH I OH ==.P-OH I OH 3086 IX. Η I C = I H =P-OH I : C I -P-OH OH COOH COOH I I x. x-c-c—γ I I PO3H2 PO3H2 wherein X and Y are each hydrogen or hydroxy; and the non-toxic salts of each of the foregoing phosphonates which in an essentially neutral aqueous solution will react with hereinafter enumerated reducing/complexing materials; i.e., stannous, ferrous, or chromous salts to form the corresponding stannous, ferrous or chromous phosphonate salt. Suitable reactive phosphonate salts (hereinafter referred to as pharmaceutically acceptable salts) for use with the present invention include sodium, potassium, •ammonium and low molecular weight substituted ammonium*fe.g., mono-, di- and triethanolamine and quaternary ammonium) salts of the above phosphonates and mixtures thereof. )86 Operable polyphosphonates of the above formula.

(I) include propane-1,2,3-triphosphonic acid; butane1,2,3,4-tetraphosphonic acid; hexane-1,2,3,4,5,6hexaphosphonic acid; hexane-l-hydroxy-2,3,4,5,6pentaphosphonic acid; hexane-1,6-dihydroxy-2,3,4,5tetraphosphonic acid; pentane-1,2,3,4,5-pentaphosphonic acid; heptane-1,2,3,4,5,6,7-heptaphosphonic acid; octane-1,2,3,4,5,6,7,8-octaphosphonic acid; nonane1,2,3,4,5,6, 7,8,9-nonaphosphonic acid; decane-1,2,3,4,5, 6,7,8,9,10-decaphosphonic acid; and the pharmaceutically acceptable salts of these acids, e.g., sodium, potassium, ammonium, triethanolammonium, diethanolammonium, and monoethanolammonium salts.

Propane-1,2,3-triphosphonic acid and salts thereof can be prepared by a process disclosed in U.S. Patent Specification No. 3,743,688.

Butane-1,2,3,4-tetraphosphonic acid and salts thereof can be prepared by a process.disclosed in U.S. Patent Specification No, 3,755,504.

The higher aliphatic vicinal polyphosphonates and salts thereof can be prepared by the process disclosed in U.S. Patent Specification No. 3,584,035 granted June 8, 1971 Among the operable polyphosphonates encompassed by the above formula (XI) are ethane-l-hydroxy-1,l-diphosphonic acid; methanediphosphonic acid; methanehydroxydiphosphonic acid; ethane-1,1,2-triphosphonic acid; propane-1,1,3,316 -13 0 8 6 tetraphosphonic acid; ethane-2-phenyl-l,1-diphosphonic acid; ethane-2-naphthyl-l,1-diphosphonic acid; methanephenyldiphosphonic acid; ethane-l-amino-1,1-diphosphonic acid; methanedichlorodiphosphonic acid; nonane-5,5diphosphonic acid; n-pentane-1,1-diphosphonic acid; tnethanedifluorodiphosphonic acid; methanedibromodiphosphonic acid; propane-2,2-diphosphonic acid; ethane2-carboxy-l,1-diphosphonic acid; propane-l-hydroxy1,1,3-triphosphonic acid; ethane-2-hydroxy-1,1, 2triphosphonic acid; ethane-l-hydroxy-1,1,2-triphosphonic acid; propane-l,3-diphenyl-2,2-diphosphonic acid; nonane1, 1-diphosphonic acid; hexadecane-1,1-diphosphonic acid; pent-4-ene-l-hydroxy-l,1-diphosphonic acid; octadec-9ene-l-hydroxy-1,1-diphosphonic acid; 3-phenyl-l,1-diphosphono-prop-2-ene; octane-1,1-diphosphonic acid; dodecane1, 1-diphosphonic acid; phenylaminomethanediphosphonic acid; naphthylaminomethanediphosphonic acid; N,H-dimethylaminomethanediphosphonic acid; N-(2-dihydroxyethyl)-aminomethane1 diphosphonic acid; N-acetylaminomethanediphosphonic acid; aminomethanediphosphonic acid; dihydroxymethanediphosphonic acid; and the pharmaceutically acceptable salts of these acids, e.g., sodium, potassium, ammonium, triethanolammonium, diethanolammonium, and monoethanolammonium salts.

Ethane-l-hydroxy-1,1-diphosphonic acid, an especially preferred polyphosphonate, has the molecular formula Cfl^C(OII) (According to nomenclature by radicals, the acid might also be named 1-hydroxyethylidene diphosphonic acid.) 3086 While any pharmaceutically acceptable salt of ethane-l-hydroxy-l,l-diphosphonic acid can be used in the practice of this invention, mixtures of the disodium and trisodium salts are most preferred. The other sodium, potassium, ammonium, and mono-, di-, and triethanolammonium salts and mixtures thereof are also suitable, provided caution is observed in regulating the total intake of cation species in the. salt composition. These compounds can be prepared by any suitable method; however, an especially preferred method is disclosed in U.S. Patent Specification Wo. 3,400,149 granted September 3, 1968.

Methanehydroxydiphosphonic acid and related compounds operable herein can be prepared, for example, by reaction of phosgene with an alkali metal dialkylphosphite. A. complete description of these compounds and a method for preparing same is found in U.S. Patent Specification No. 3,422,137 granted January 14, 1969.

Methanedihydroxydiphosphonic acid and salts useful herein and a method for preparing same are disclosed in U.S. Patent Specification No. 3,497,313 granted February 24, 1970.

Methanediphosphonic acid and related compounds useful herein are described in detail in U.S. Patent Specification No. 3,213,030, granted October 19, 1965. A preferred method of preparing such compounds is disclosed in U.S. Patent Specification No. 3,251,907 granted May 17, 1966.

Ethane-1,l,2’-triphosphonic acid and related compounds which can be used in the compositions of this invention, as well as a method for their preparation, - 18 4 3 0 8 6 are fully described in U.S. Patent 3,551,339 granted December 29, 1970.

Propane-1,1,3,3-tetraphosphonic acid and related compounds useful herein, and a method for preparing same, are fully disclosed in U.S. Patent 3,400,176 granted September 3, 1968. The higher methylene interrupted methylene diphosphonate polymers can be prepared by the polymerization of ethylene-1,1-diphosphonate.

Pentane-2,2-diphosphonic acid and related compounds can be prepared in accordance with the method described by G. M. Kosolopoff in J, Amer. Chem. Soc., 75, 1500 (1953).

Operable phosphonates of formula (III) above include the following: Methanecyclobutylhydroxydiphosphonic acid Methanecyclopentylhydroxydiphosphonic acid Methanecyclohexylhydroxydiphosphonic acid Methanecycloheptylhydroxydiphosphonic acid * Metlianecyclooctylhydroxydiphosphonic acid Methanecyclononylhydroxydiphosphonic acid Methanecyclodecylhydroxydiphosphonic acid.

Each of the sodium, potassium, ammonium, monoethanolammonium, diethanolammonium, and triethanolammonium salts of the above-recited methanecycloalkylhydroxydiphosphonic acids as well as any other pharmaceutically acceptable salt of these acids, also selectively seek the skeleton.

The phosphonates of formula (III) can be prepared by methods fully described in U.S. Patent 3,584,125, granted June 8, 1971. 4308« The preferred phosphonates of formula (IV) for the purpose of this invention are tris(phosphonomethyl) amine; tris(1-phosphonoethyl) amine; tris(2-phosphono-2propyl)amine; and their pharmaceutically acceptable salts. Tris (phosphonomethyl)amine is especially preferred. The following are exemplary of compounds which can also be used: (a) bis(phosphonomethyl)-1-phosphonoethyl amine; (b) bis(phosphonomethyl)-2-phosphono-2-propyl amine; (c) bis(l-phosphonoethyl)phosphonorcethyl amine; (d) bis(2-phosphono-2-propyl)phosphonomethyl amine; (e) tris(1-phosphono-l-pentyl)amine; (f) bis(phosphonomethyl)2-phosphono-2-hexyl amine; and (g) the pharmaceutically acceptable salts of acids (a) to (f), e.g. , sodium, potassium, ammonium, triethanolammonium, diethanolammoniuw, and monoethanolammonium salts.

The tris(phosphonoalkyl)amines cart be prepared, for example, by first preparing the corresponding ester in accordance with the general reaction: R. '1 R. 3(RO)2P(O) (Η) + 3 C®0 + NH3-» I(RO)2-P-C]3N R. ‘2 R. '2 wherein R is alkyl and and R2 are hydrogen or lower alkyl.

The free acids can be prepared by hydrolysis of S the ester using strong mineral acids such as hydrochloric acid. The salts are, of course, prepared by neutralizing the acid with the base of the desired cation. The preparation of tris (phosphonoalkyl)amines is fully disclosed by Irani, et al., in Canadian Patent 753,207, issued February 21, 1967.

The phosphonates of formula (V) include the following: ; (1) 3,3,4,4,5,5-hexafluoro-l,2-diphosphonocyclopent-l-ene; (2) 3,3,4,4-tetrafluoro-l,2-diphosphonocyclobut-l-ene; and (3) 3,3,4,4,5,5,6,6-octafluoro15 1,2-diphosphonoeyclohex-l-ene.

The perfluorodiphosphonocycloalkenes can be prepared, for example, by reacting trialkyl phosphites with 1,2-dichloroperfluorocycloalk-l-enes in accordance with the procedures fully described by Frank in J, Org, Chem., 31, #5, p. 1521.

The phosphonate of formula (VI) is referred to herein as cyclic tetraphosphonic acid. This compound )86 and its pharmaceutically acceptable salts can be prepared by any suitable method; however, an especially preferred method is disclosed by Oscar T. Quimby, U.S. Patent 3,387,024 granted June 4, 1968.

Operable phosphonates encompassed by the above formula (VII) are ethene-1,2-dicarboxy-l-phosphonic acid; and the pharmaceutically acceptable salts of this acid, e.g., sodium, potassium, ammonium, triethanolammonium, diethanolammonium, and monoethanolammonium salts. While the above formula (VII) is representative of cis-isomers, the corresponding trans-isomers are also useful herein.

Reference hereinafter to ethene-1,2-dicarboxy-l-phosphonic acid or salts thereof, unless otherwise specified, is intended as contemplating the cis- and trans-isomers and mixtures thereof.

Ethene-1,2-dicarboxy-l-phosphonic acid and related compounds useful herein can be prepared by reaction of an ester of acetylenedicarboxylic acid and a dialkyl » phosphite followed by hydrolysis and saponification.

This method is more fully described in U.S. Patent Specification No. 3,584,124 granted June 8, 1971.

The sodium salt of formula (VIII) can be made by the rearrangement reaction of a 2-haloethane-l-hydroxy1,1-diphosphonic acid with about 3 equivalents of sodium hydroxide as disclosed in U.S. Patent Specification No. 3,641,125 The phosphonate of formula (IX) can be made by the method of German Offenlegunsschrift 2,026,078.

Operable carboxyphosphonates of the above formula (X) include ethane-1,2-dicarboxy-l,2-diphosphonic acid; 3 0 8 6 ethane-1,2-dicarboxy-l,2-dihydroxy-l,2-diphosphonic acid; ethane-1,2-dicarboxy-l-hydroxy-l,2-diphosphonic acid; and the pharmaceutically acceptable salts of these acids, e.g., sodium, potassium, ammonium, triethanolammonium, diethanolammonium and monoethanolammonium salts.

Ethane-1,2-dicarboxy-l,2-diphosphonic acid, a preferred carboxyphosphonate herein, has the molecular formula CH(COOH)(PO3H2)CH(COOH)(PO3H2). The most convenient crystallizable salts of this acid are obtained when three, four or five of the acid hydrogens are replaced by sodium.

While any pharmaceutically acceptable salt of ethane-1,2-dicarboxy-l,2-diphosphonic acid can be used a in the practice of this invention, the tetrasodium dihydrogen salt, the trisodium trihydrogen salt, the disodium tetrahydrogen salt, the monosodium pentahydrogen salt, and the mixtures thereof are useful. The other potassium, ammonium, and mono-, di-, and triethanolammonium, etc., salts and mixtures thereof are also suitable, provided caution is observed in regulating the total intake of cation species in the salt composition.

Ethane-1,2-dicarboxy-l,2-diphosphonic acid and suitable salts thereof can be prepared in any convenient manner. For example, the reaction described by Pudovik in Soviet Research on Organo-Phosphorus Compounds, 1949-1956, Part III) 547-85c. can be used to prepare the ester of ethane-1,2-dicarboxy-l,2-diphosphonic acid which in turn can, by ordinary hydrolysis reactions, be converted S086 to the free acid. form. Neutralization by alkali compounds such as sodium hydroxide, potassium hydroxide, carbonates and the like can be used to prepare a desired salt of the acid. A more detailed description of the preparation of these compounds is described in U.S. Patent Specification No. 3,562,166 granted February 9, 1971.

Ethane-1,2-dicarboxy-l,2-dihydroxy-l,2-diphosphonic acid and related compounds useful herein can be prepared by reaction of an ester of ethane-1,2-dicarboxy-l, 2diphosphonic acid and an alkali metal hypohalite followed by hydrolysis and saponification. This method is more fully described in U.S. Patent Specification No. 3,579,570 granted May 18, 1971.

Mixtures of any of the foregoing phosphonic acids and/or salts can be used in the practice of this invention.

In a highly preferred embodiment of this invention, mixtures of disodium- and trisodium-ethane-l-hydroxy-I,1diphosphonate salts,wherein the mole.ratio of the disodium salt to trisodium is from about 4:1 to 1:1, more preferably 3:1 to 1:1, are employed in the pertechnetate reducing agent along with an ascorbic acid compound and a reducing metallic ion. These preferred phosphonate/ reducing ion/ascorbic acid compound mixtures provide especially good scintiscans (excellent stability and skeletal uptake and little soft tissue uptake).

However, it is preferable to limit the amount of stahnous, chromous or ferrous salts of the poiyphosphonates to no more than about 10% of the total.

The following examples are illustrative of compositions made according to this invention (the quantities of each component being in milligrams): 386 σι Η σι <Μ 10 *—J Ο Γ*· CM •Ή Ο ω cd cd » « Ο Γ* Ο CM ιΰ γΗ Ο Η Η Η > σι ιη rH « Ο σι ιη cd Ο r> CM <0 σι rd Η « β • ιη Ο Γ· ο ί> Η Ι-ί Η σι ιη σι W σι m σι ιη σι m Φ cd β Ο 10 cd Ο Γ* CN ω rH Ο Γ** «Μ CM cd Ο Γ*» CM I-1 ο 10 rd rd Ο Γ* ο CM I Ο ·Η 1 rd Φ «Ρ □ rd -Ρ Φ «π >. rH φ C γ-4 1 C 0 0 Φ 1 0 33 •Η Ρ >1 κ 33 04 0 φ X 0 04 ιη 0 33 0 Μ in 0 33 Ρ F-4 Ρ Ό 0 33 04 0 gj τ) >1 33 0< ιη ϋ Μ X 33 Pi •Η 0 Μ 33 1 Ή Ό 33 φ Ο ι-Η Ό 04 04 cd 1 Φ •Η Φ φ Φ ε S I ω Φ C Ή Φ φ Ρ 0 ο 0) φ G Φ C Φ Φ •Η Φ •Η Φ Ρ Ρ Φ Ή υ C -Ρ φ -ρ ra 33 0 Ρ Ρ Ρ Ό φ φ Λ 0 (0 (β 33 Φ rC Ρ (0 0 Φ 0 •Η Λ Ό 33 Ρ 0 Λ £ -ρ cr -Ρ φ 33 rd Ψί rd Ρ Ρ •Η Ρ 0 6 μ 0 Φ 0 Φ 6 Ρ 33 rd 33 0 0 ϋ 0 □ £ « ,ό I 33 £ φ υ 0 υ t—1 0 Φ υ ιη φ ι ft έ λ Ε Ε ιη 33 ιη V) φ γΗ Η ΙΛ 0 ΙΠ £♦ 3 0 ω ιη υ φ υ φ 0 d 0 •Η 0 3 •Η Ρ 0 ιη 0 φ •Η Ε C •Η .C Ό 33 •Η Ό 0 ο 0 0 Ε ω Ε Λ t—1 0 φ Ό ft 0 04 τ3 0 rd 0 0 Ρ. 0 0 0 Ρ >1 •Η 33 0-Η W ·Η 0 ιη 0 Ρ 0 •Η υ •Η 0 33 ο Ρ (η Ό •Η Ό ιη •Η 0 Φ Ρ Ρ Ό 0 Τ3 □ Ρ rd Φ •Η Ρ Ή Ρ •Η Ρ φ £ 0 ι-Η 0 ιη Φ Φ *Η Q &< α Η Q W &4 υ W Ο ω Ζζ υ α ο rH ιη Η Each of the above compositions, upon the addition of about 5 ml. of a pertechnetate-99m solution, and thorough shaking, yields a skeletal-scanning agent suitable for intravenous injection into a human patient having a stability of more than three hours. Preferably, about 1 ml. of solution is used in an adult of about 50-100 kilograms body weight and is injected slowly, over a period of about 30 seconds. Administration is preferably done within about three hours of preparation. Compositions- can, of course, contain multiples or fractions of the above amounts to allow preparation of sufficient agent from a single composition to perform any desired number of scans.

The following example is illustrative of a pertechnetate solution having dissolved therein an ascorbic acid compound: ' EXAMPLE XI A collecting vial containing Θ.1 mg. of sodium ascorbate is placed at the elute orifice of a pertechnetate99m generator. Saline elute is collected in the vial and completely dissolves the sodium ascorbate.

Approximately 5 ml. of the pertechnetate solution, with dissolved sodium ascorbate, is added to a pertechnetate reducing agent comprising 5.9 mg. of the sodium salt of ethane-l-hydroxy-1,l-diphosphonic acid and 0.16 mg. of stannous chloride. After 386 thorough shaking, a stable scanning agent suitable for intravenous injection into a human patient is prepared In the above example, sodium ascorbate is replaced by equivalent amounts of ascorbic acid, methyl ascorbate, ethyl ascorbate, isopropyl ascorbate butyl ascorbate, diethanolamine ascorbate, calcium ascorbate, magnesium ascorbate, potassium ascorbate, stannous ’ascorbate, and tetramethylaromonium ascorbate, and stable scanning agents are prepared.

Claims (16)

CLAIMS:

1. A method of preparing a technetium-99m-based scanning agent from an oxidized pertechnetate solution, the method comprising codissolving in the solution a pertechnetate reducing agent and no more than 0.1% by weight of the solution of ascorbic acid or a pharmaceutically acceptable salt or ' ester thereof.

2. A method according to Claim 1 wherein the pharmaceutically acceptable salt is sodium ascorbate.

3. A method according to Claim 1 or 2 wherein Said pertechnetate reducing agent is a metallic salt of sulfuric or hydrochloric acid.

4. - A method according to any of Claims 1 to 3 wherein the pertechnetate reducing agent is a stannous, chromous or ferrous salt.

5. A method according to Claim 3 or 4 wherein said pertechnetate reducing agent is stannous chloride, chromous chloride or ferrous sulfate.

6. A method according to any of Claims 1 to 5 comprising codissolving an organ-specific carrier in the oxidized pertechnetate solution.

7. A method according to Claim 6 wherein said organ-specific carrier is the sodium salt of ethane-l-hydroxy-l,l-diphosphonic acid.

8. A method according to Claim 6 wherein said organ-specific carrier is selected from methane diphosphonic acid, dichloromethane diphosphonic acid and pharmaceutically acceptable salts thereof. 63086

9. A composition, useful in the preparation of technetium99m-based radiographic scanning agents according to the method of any of Claims 1 to 8, the composition comprising a pertechnetate reducing agent and an effective amount, no more than 25% by weight, of a pharmaceutically acceptable salt or ester of ascorbic acid.

10. A composition according to Claim 9 comprising no more than 10% by weight of the pharmaceutically acceptable salt or ester of ascorbic acid.

11. A composition, useful in the preparatiofl of technetium-99m based radiographic scanning agents according to the method of any of Claims 1 to 8, the composition comprising a pertechnetate reducing agent selected from stannous or chromous salts, and an effective amount, no more than 25% by weight, of ascorbic acid.

12. A composition according to Claim 11 comprising no more than 10% by weight of ascorbic acid.

13. A composition according to Claim 9 substantially as hereinbefore described with reference to any one of Examples I, III to VI, and VIII to X.

14. A composition according to Claim 11 substantially as hereinbefore described with reference to Examples II or VII.

15. A composition useful in the preparation of technetium-99mbased radiographic scanning agents according to the method of any of Claims 1 to 8, the composition comprising an oxidized pertechnetate solution having dissolved therein an effective amount, no more than 0.1% by weight of ascorbic acid or a pharmaceutically acceptable salt or ester thereof.

16. A technetium-99m-based scanning agent when produced by the method of any of Claims 1 to 8.