Use of paramagnetic complex salts for the preparation of agents for NMR diagnostics.

The invention relates to the use of physiologically compatible paramagnetic complex salts for the preparation of agents for NMR diagnostics. These complex salts consist of aminopolycarboxylic acids of the formulas I to IV<chemistry id="chem0001" num="0001"><img file="EP0169299A2_D0001.tif" /></chemistry>N-hydroxyËthyl-N, N ', N'-Ëthylenediamine-triacetic acid (HEDTA),<chemistry id="chem0002" num="0002"><img file="EP0169299A2_D0002.tif" /></chemistry>N, N, N ', N ", N" -diathylenetriaminepentaacetic acid (DTPA),<chemistry id="chem0003" num="0003"><img file="EP0169299A2_D0003.tif" /></chemistry>N-hydroxyethyliminodiacetic acid<chemistry id="chem0004" num="0004"><img file="EP0169299A2_D0004.tif" /></chemistry><ul id="ul0001" list-style="none"><li>where m is the numbers 1 to 4,</li><li>n the numbers 0 to 2,</li><li>R¹ a saturated or unsaturated hydrocarbon radical having 4 to 12 hydrocarbon atoms or the group -CH₂-COOH represents</li></ul>or

Diphosphonic acids of the general formula V<chemistry id="chem0005" num="0005"><img file="EP0169299A2_D0005.tif" /></chemistry>wherein<ul id="ul0002" list-style="none"><li>R₂ Hydrogen, alkyl with 1 to 4 carbon atoms, halogen, the hydroxyl, amino or CH₂-COCH group and</li><li>R₃ Hydrogen, alkyl with 1 to 4 carbon atoms, the -CH₂-COOH group or if R₂ represents halogen, also mean halogen,</li></ul>and<ul id="ul0003" list-style="none"><li>the ions of the lanthanide elements of atomic numbers 57 to 70 or the ions of the transition metals of atomic numbers 21 to 29, 42 and 44</li><li>and optionally sodium hydroxide as the base.</li></ul>

Preferred complexing agents are N, N, N ', N'-ethylenediamine-tetraacetic acid (EDTA), N, N, N', N ", N" -diethylenetriamine-pentaacetic acid (D._TPA) and ethane-1-hydroxy-1,1-diphosphonic acid, methane-diphosphonic acid and ethane-1-amino-1,1-diphosphonic acid.

These complexes have not previously been used as NMR diagnostics. For example, praseodymium, neodymium, europium-EDTA or praseodymium, gadolinium, ytterbium-EDTA-ammonium and pyridinium complexes, as described in J. Am. Chem. Soc. 98, 3726 (1976) and J. Am. Chem. Soc. 99, 1762 (1977), have only been used for physical examinations.

Up to now, only the copper, cobalt and iron metal salts of EDTA have been used in human medicine: In the patent FR-A-988 M (Laboratoires Gerda) the copper (II) EDTA and its disodium salt are used as agents for the treatment of Rheumatism described; the patent FR-A-484 M (Fabriques de produits chimiques Billault) deals with the iron (II) salt of the iron (III) complex of EDTA as an agent against anemia; The patent FR-A-1 111 504 (Cassella Farbwerke Mainkur) describes the disodium and dipotassium salt of the cobalt complex of EDTA as a therapeutic agent for blood formation. So far, neither these nor other complex salts according to the invention with the compounds of the formulas I to V have been used for NMR diagnostics.

Wehn required, it is also magical to bind the complex compounds according to the invention to biomolecules, so that the complex compounds can be transported to specific locations in the living body. Immunoglobulins, hormones such as insulin, glucagen, prostaglandins, steroid hormones, proteins, peptides, aminosugars, lipids are used as biomolecules, for example

The coupling of the paramagnetic complex salts to the desired biomolecules _kOils occur according to known methods, for example by reacting the nucleophilic group of a biomolecule such as the amino, phenol, sulfhydryl or imidazole group with an activated derivative of the complex compound.

Examples of suitable activated derivatives are acid chlorides, mixed anhydrides (which can be prepared from the carboxyl derivative of the complex compound with chlorocarbonic acid ester), activated esters, nitrenes or isothiocyanates.

It is also possible to react an activated derivative of the biomolecule with a nucleophilic derivative of the complex compound.

Inorganic bases, such as sodium hydroxide, are used as bases for salt formation.

The new agents are prepared in a manner known per se by dissolving the paramagnetic complex salt in water or physiological salt solution, optionally with the addition of additives customary in galenicals, such as, for example, physiologically compatible buffer solutions (for example sodium dihydrogen phosphate solution) and sterilizing the solution. The aqueous solutions can be administered orally, neural and in particular intravascularly. If suspensions of the paramagnetic complex salts in water or physiological saline solution are particularly desired for oral administration, the paramagnetic complex salt is mixed with one or more adjuvants and / or surfactants and / or flavorings customary in galenics for taste correction and before oral use in water or physiologically Saline solution suspended. 3 to 10 g of paramagnetic complex salt and 2 to 8 g of one or more auxiliaries, such as sucrose, highly disperse silicon dioxide, polyoxyethylene polyoxypropylene polymers, starch, magnesium stearate, sodium lauryl sulfate, talc, lactose; Carboxymethyl cellulose sodium.

For NMR diagnosis in humans, aqueous solutions or suspensions are used which contain 5 to 250 mmol / l, preferably 50 to 200 mmol / l, of a paramagnetic complex salt. The aqueous solutions are in the pH range between about 6.5 and 8.0, preferably between 6.5 and 7.5.

The complex formation according to the present invention detoxifies the paramagnetic salts, and it is also achieved that the salts are stable and readily soluble in water even in the physiological pH range.

The new agents appear particularly suitable in the form of complex salt solutions for better differentiation b_e.g.w. Localization of pancreatic lesions

and the liver, as well as tumors and bleeding in the cranial area. To diagnose the item to be examined_Areals, for example, becomes an aqueous one, to the blood _iSonic solution of paramagnetic complex salts administered intravenously in a dose of 1 to 100 µmol / kg. At a concentration of the complex salt of 50 to 200 mmol / l for a

Human examination requires about 1 to 50 ml of solution. The layer of interest is recorded approximately₁₅ up to 60 minutes after the intravenous application of the aqueous solution of the paramagnetic complex salt.

The physical diagnostic methods that are common in medical practice and that can be carried out without or with only minor surgical interventions are, for example, X-ray irradiation of the body, scintigraphy and sonography. All of these methods are either associated with health risks or their scope is restricted. For example, the patient is exposed to the ionizing radiation in X-ray techniques and in scintigraphy, so that these methods cannot be used as often or not at all in high-risk groups, such as, for example, in infants and pregnant women.

Sonography does not have the disadvantages mentioned, but its scope is very limited, especially in the cranial area.

Since it has so far not been possible to completely eliminate the disadvantages described, in spite of the great effort involved in research, imaging processes are sought which do not have these disadvantages but which provide comparable information for diagnosis.

One of these imaging methods is nuclear spin tomography (spin imaging, stuff matography), which is based on the physical effect of so-called nuclear magnetic resonance (NMR). This diagnostic procedure enables sectional images of the living body and insight into metabolic processes to be obtained without the use of ionizing radiation. The effect of nuclear magnetic resonance is shown by atomic nuclei which - like hydrogen, which is mainly present in water in biological tissue - have a magnetic moment and are therefore aligned in a strong external magnetic field. A high-frequency pulse (resonance frequency) brings them out of their equilibrium position, into which they return at a characteristic speed. The duration of the return to equilibrium, the so-called relaxation time, provides information about the degree of order of the atoms and their interaction with their surroundings.

The visual representation obtained by measuring the proton density or the relaxation times is of high diagnostic value and provides information about the water content and the condition of the examined tissue. For example, tumor tissue shows longer relaxation times than healthy comparative tissue. (A. Ganssen et al. Computed Tomography l, / 1981 / pp. 2-10; Georg Thieme Verlag, Stuttgart, New York).

It has now been found that paramagnetic ions, such as Mn²⁺ (Manganese) or Cu2f (Eupfer) influence the relaxation times and thus increase the information content.

The heavy metal salt solutions previously used for this purpose on the test animal are unsuitable for intravenous administration to humans because of their high toxicity. One is therefore looking for paramagnetic substances that are well tolerated and have a favorable effect on imaging. The latter can take place, for example, in that the spin-lattice relaxation time T is as specific as possible to the organ_l is greatly reduced, while at the same time the spin-spin relaxation time T₂ is kept largely constant. It has now been found that the desired detoxification of the otherwise toxic metal salts can be carried out by complexing, without adversely affecting the paramagnetic properties. The latter is surprising since it is known that this changes the distribution of the d or f electrons over the d or f orbitals.

The paramagnetic complex salts are prepared by processes known to those skilled in the art by dissolving the paramagnetic metal salt of the lanthanide elements of atomic numbers 57 to 70 or the transition metals of atomic numbers 21 to 29, 42 and 44 in water and / or alcohol and by dissolving the equivalent Amount of complexing agent added to water and / or alcohol and stirred, if necessary with heating to 50 ° C to 120 ° C until the reaction is complete. If alcohol is used as a solvent, methanol or ethanol is used. If the complex formed is insoluble in the solvent used, it crystallizes and can be filtered off. If it is soluble, it can be isolated by evaporating the solution to dryness.

The following examples are intended to explain the invention in more detail.

example 1

a) Preparation of the Manganese II Complex of Ethylenediamine-Tetraacetic Acid:

The suspension of 6.17 g of manganese II carbonate in 500 ml of water is mixed with 14.6 g of ethylenediaminetetraacetic acid and heated with stirring on the steam bath, with evolution of gas occurring. The initially pink color disappears after approx. 20 minutes and everything is in solution except for a small residue: after stirring for an hour at 110 ° C, the undissolved solution is filtered off and the filtrate is cooled. After standing for 15 hours, the crystals are filtered off and dried: K₁= 14.1 g (molecular weight 345.17) mp: 256 ° / 258-259 ° C.

b) Preparation of a solution of the disodium salt of the manganese (II) complex of ethylenediamine-tetraacetic acid:

5.55 g (15 mmol) of the manganese (II) complex of ethylenediaminetetraacetic acid (water content: 6.9%) are dissolved in 80 ml of water with the addition of dilute sodium hydroxide solution at pH 7.5. the solution is then made up to 170 ml with water pi, filtered in ampoules and heat-sterilized.

Example 2

Preparation of the gadolinium III complex of diethylenetriaminepentaacetic acid:

The suspension of '435 g gadolinium oxide (Gd₂0₃) and 944 g of diethylenetriamine-pentaacetic acid in 12 liters of water are heated to 90 ° C. to 100 ° C. with stirring and stirred at this temperature for 48 hours. The undissolved matter is then filtered off and the filtrate is evaporated to dryness. The amorphous residue is pulverized. Yield 144 g; (Molar weight 547.58)

Fp .: melts from 235 ° and remains undecomposed up to 320 ° C.

If one or more acidic group (s) is (are) still present in the paramagnetic complex compound obtained, the complex compound obtained can then, if desired, be dissolved or suspended in water and mixed with the desired inorganic base until the neutral point is reached. After filtering undissolved portions, the solution is evaporated and the desired complex salt is obtained as a residue.