IE44586B1 - Liquid injectable niclofolan formulations - Google Patents

Abstract

1505487 Bis (5 - chloro - 2 - hydroxy - 3 - nitrophenyl) injections BAYER AG 18 Jan 1977 [22 Jan 1976] 01918/77 Heading A5B An injectable liquid preparation comprises (a) bis (5 - chloro - 2 - hydroxy - 3 - nitrophenyl), (b) a base, (c) polyvinylpyrrolidone and (d) water.

Description

The present invention relates to new liquid formulations of the known substance 5, 5' -dichloro-2,2'dihydroxy-3,3'-dinitrodiphenyl (hereinafter referred to as Niclofolan).

Formulations of the substance Niclofolan, which has an action against liver fluke, have already been disclosed.

The formulation as a tablet for oral administration is predominant. For this purpose, the active compound Niclofolan is provided with a coating which is resistant to the rumen juices, as is described, for example, in German Offenlegungsschrift (German Published Specification) 2,107,917.

However, these formulations for oral administration have a number of disadvantages. Moreover, oral administration is very laborious and, especially in the case of larger animalB, is ?5 associated with considerable difficulties. There has, therefore, been no lack of attempts to develop an injection formulation which can be administered, and dosed, more easily by the veterinary surgeon.

On injection of the active compound Niclofolan in ths form of the injection formulations known hitherto it has been found that this compound is highly toxic to the tissues and that necrosis results. Moreover, when aqueous suspensions of i Niclofolan were injected, the depot o-f active compound at the point of injection was not broken down. When solutions of the active compound Niclofolan in organic solvents were injected, the active compound again precipitated at the point of injection and was not broken down there. A depot of active compound of this type can, however, not be tolerated since, on the one hand, there is a danger that a depot of aotive compound of this type will be eaten with the meat and, « 1458« on the other hand, a Niclofolan—blood level value which is too high is maintained for too long as a result of this depot, the consequence of this being that the animal cannot be. released for slaughter during thisperiod. The addition of emulsifiers with solubilising properties, such as, for example, polyoxyethylated castor oil, to injection formulations of Niclofolane in organic solvents does indeed reduce the tendency to crystallise out at the point of injection but the active substance Niclofolane was found to be still so toxic to the tissues that these experiments were not able to lead to a formulation which could be used.

According to the present invention, we now provide a liquid injectable formulation of Niclofolan which contains, in addition to the active compound, one or more physiologically tolerable bases, polyvinylpyrrolidone and water. Optionally, a further organic solvent which is miscible with water may also be incorporated in the formulation. The formulations of the invention display a very good tolerance (especially tissue tolerance) in animal experiments.

Thus, it has been found that two factors are essential in order to obtain an injectable formulation of Niclofolan which can be used and is tolerated well, that is to say the formation of a salt and the addition of polyvinylpyrrolidone (frequently abbreviated +·« SVP in the text which follows).

It is to be regarded as extremely surprising that the injectable formulations of Niclofolan, according to the invention, ere tolerated so well by animals since this was not the case with injection formulations of Niclofolan known hitherto.

The injectable Niclofolan formulations according to the invention thus represent a genuine advance in veterinary medicine. The invention therefore further provides a method id see of combating (including the prevention, relief and cure of) liver fluke in non-human animals which comprises Injecting the animals with a formulation of the invention.

As already mentioned above, the tissue tolerance can, surprisingly, be markedly improved by the formation of a watersoluble salt of the active compound Niclofolan, which contains phenol groups, with a pharmaceutically suitable base.

Only one of the two phenolic hydroxyl groups in Niclofolan can be used to form salt if the solution prepared therewith is to have pH value which is physiologically acceptable, This can be seen from the titration curve for the active compound with sodium hydroxide solution, (See the accompanying Figure).

In. .this case, the range from pH 4 to pH 10 is to be regarded as the physiologically acceptable range of pH values. 1>5 The Figure shows the titration curve for 6.9 g of Niclofolan active compound dissolved in dimethylformamide (2/100 mol) titrated with 1 N NaOH. The ordinate gives the amount of NaOH in grammes and the abscissa gives the pH value of the solution.

The salt is preferably not prepared separately and then dissolved but is immediately brought into the dissolved form, in the solution to be injected, by adding the base to the suspension of active compound, or vice versa. Salt which has been isolated displays a gel effect1*, which impedes the dissolution.

In principle, all the physiologically acceptable inorganic and organic bases can be used to form the phenolate. However, those bases which are soluble in water and give a soluble salt at a pH value below 10 are preferred.

Thus,for example, on the addition of sodium hydroxide solution or triethylamine, the active compound dissolves to give a clear solution only at a pH of 10. With other bases, 11586 however, a clear solution is already formed at pH 8 - 9.

Bases of this type are preferably organic bases, for example: basic amino acids, such as 1- and D, L-arginine and I- and /, 1-lysine, methylglucamine, glucosamine, triethanolamine, diethanolamine, monoethanolamine or 2-amino-2-hydroxymethyl-propane-1, 3-diol. Salts with a diamine are also suitable} thus, for example, Ν,Ν,Ν' ,N'-tetrakis-(2-hydroxypropyl)-ethylenediamine forms a soluble salt at pH 8.3 and, furthermore, for example, a polyether-tetraol based on ethylenediamine, (molecular weight 480 - 520, OH Index 432 - 467) also forms a soluble salt in the physiologically acceptable pH range.

With all the bases employed, a gel is formed when the salt is formed in a weakly alkaline medium. She gel formation decreases as the pH value increases. Therefore, the base is preferably employed somewhat in excees of the molar ratio of £ to 1 in order to obtain pH value of between 8 and 10. It is therefore appropriate to employ water-soluble bases.

Shis can be demonstrated by the following experiment: Niclofolan salt solutions (active compound content 5%) with a pH of 9.3, 9·4, 9.5, 9.6, 9·7 and 9.8 were prepared from a Niclofolan suspension and N-methylglucamine. Up to pH 9.6 the solutions formed stiff gels, a soft gel was formed at pH 9.7 and at 9.8 the formation of a gel ceased in favour of a viscous solution. At pH values of up to pH 9.7 the active compound crystallised out of the gels again after some time.

She injectable Niclofolan formulations according to the invention generally contain from 1 to 10 per cent by weight, and preferably from 2 to 7 per cent by weight, of Niclofolan and from 3 to 25 per cent by weight, and preferably from 5 to 20 per cent by weight, of a physiologically acceptable, preferably organic, baee, the corresponding salt being formed when 44588 the lliclofolan active compound and the base are added together.

The polyvinylpyrrolidone (PVT) employed preferably has a molecular weight of from 10,000 to 160,000, and desirably of from 10,000 to 40,000, in a concentration of between 5 and 25 per cent, and preferably of between 10 and 20 per cent, (weight/ weight).

As it ira,s possible to deteimine according to the invention, the addition of PVP is indispensable for the following reasons: 1) After the addition of PVP, the mass which is formed at a low pH value and which hitherto was gelatinous surprisingly liquefies. Thus, when 5$ of PVP are added to the gels described above, clear solutions are obtained without the formation of a gel and without precipitation. b) Subsequent thickening of a solution with a higher pH value is prevented by the addition of PVP. c) The salts are prevented from crystallising out in the formulation. d) The addition of PVP additionally improves the tissue tolerance of the Nielofolan salt solution.

The injectable lliclofolan formulations according to the invention also contain water, preferably in concentrations of from 40 to 90, and more preferably from 55 to 80, per cent by weight. The injectable Hiclofolan formulations according to the invention also optionally contain further water-miscible organic solvents, preferably monohydric and/or polyhydric alcohols, examples which may be mentioned being ethanol, npropanol, i-propanol and polyethyleneglycol with a molecular weight of 200 to 400. These water-miscible organic solvents may, in general, be added in concentrations of from 1 to 50, preferably from 5 to 20, per cent by weight.

The formation of the salt of lliclofolan thus leads, as described above, to a water-soluble product, which, surprisingly, is better tolerated than the pure Niclofolan active compound.

However, a pure salt solution would not yet be sufficiently well tolerated and would be too viscous for a Niclofolan injection formulation which meets the requirements in practice. It would have to be employed at too hi.rji a pH value, that is to say a pH value which is outside the physiologically acceptable pH range, or in too great a dilution.

Surprisingly, it is now possible - as described above further adequately to reduce the viscosity, and at the same time additionally to increase the tissue tolerance, by the addition of PVP. Surprisingly, a very good injectable Niclofolan formulation, which can be prepared with an adequate concentration of 1 to 10, and preferably 2 to 7»per cent by weight of Niclofolan active compound, results from the combination of salt formation and the addition of PVP. Precipitation of the active compound, that is to say Niclofolan, is prevented in this case, even to an extent such that no Niclofolan active compound separates out in the liquor of the animal after the injection. Phe significance of this question is generally recognised by specialists in the field (see,for example, H.G. Schroeder and P.P. des luca, Bull. Par. Drug Assoc. 28 (1), 1 (1974)).

The active compound employed according to the invention, that is to say Niclofolan (S^'-dichloro^^'-dihydroxy-S,^dinitrodiphenyl) is already known (see, for example, U.S.

Patent 3,082,151).

The injectable Niclofolan formulations according to the invention can be prepared using any desired sequence of the mixing steps, that is to say using any desired sequence of addition of Niclofolan, the pharmaceutically suitable base and the polyvinylpyrrolidone in aqueous solution, optionally with the addition of a water-miscible organic solvent.

Preferably, an active compound suspension of Niclofolan in water is first prepared, optionally with the addition of a water5 miscible organic solvent, and the further constituents of the Niclofolan injection formulations according to the invention, that is to say the organic base and the polyvinylpyrrolidone, are then added, whilst stirring continuously.

The resulting solution is preferably stirred with a high10 speed stirrer, then filtered, filled into a container and sterilised under water or steam in a known manner (for example at12O°C and 1 atmosphere for at least 20 minutes).

The experiments which follow are intended to illustrate the tolerance, the ease of administration and the plasma level values ' (blood level values) of the Niclofolan injection formulations described in the preparation examples which follow. 1. Tolerance experiments Tolerance experiments were carried out on cattle pro injeotione with the injectable Niclofolan formulations analo20 gous to Preparation Examples 1 and 2. The formulation was administered subcutaneously in the right-hand side or the lefthand side of the neck of the test animals. The single subcutaneous administration led to minimal swellings up to 3 days after treatment in the case of only a few animals.

It was not possible to determine any differences between the formulations tested with regard to their local tolerance.

No general intolerance phenomena were found.

The results are illustrated by Table 1 which follows. 4 5 8b' Table 1 Niclofolan formulations, pro injectione; Test of the tolerance in cattle after three subcutaneous adminis trations Number Formulation Dose Admini- Tolerance in days after of according to in stration treatment* animals positional mg/kg example No. 1357 2 2 0.75 subcuta- 0/2/2 neous 0/2/2 0/2/2 0/2/2 2 2 1.00 subcuta- 1/1/2 neous 1/1/2 0/2/2 0/2/2 2 1 0.70 subcuta- 0/2/2 neous 0/2/2 0/2/2 0/2/2 2 1 •The sequence x = number of y = number of 1.00 subcuta- 1/1/2 1/1/2 neous of numbers x/y/z denotes swellings points of injection without findings 0/2/2 0/2/2 z = total number of points of injection After only 5 days no swellings of any type could any longer be detected in the individual test animals.

When a Niclofolan fonaulation consisting of 2% of the active compound in N-methylpyrrolidone, weight/volume, was employed, swellings and necrosis at the particular point of injection could still be detected even 14 days after the treatment.

Ease of administration All the f ormulations tested could be administered very easily. Determination of the blood level Comparative plasma level investigations were carried out on cattle with injectable Niclofolan formulations according to Example 1 and 2, by subcutaneous and intramuscular injection, and with Niclofolan tablets. 4» 8 6 The blood level values found were distinctly higher in the case of the Niclofolan formulations according to the invention than in the case of the tablet formulations.

The highest blood level values were obtained after intra5 muscular injection. (See Table 2 which follows for further details).

Table 2 Hiclofolan/determination of the blood level/plasma concentrations in cattle β φ ρ d G d O β Λ β o •ri P d β P CQ ♦H β £ O CTi +3 X5 >> UO »d «η - 0) φ a Η Ή Ρ o -Ρ Φ · d ft o O 03 £5 β o •rl P d Ih O ft «d* O CM CJ CM m ka vo cm ka cm ka cm > • · · ka Tf ka UA KA CM • ♦ · UA £— O UA Txj- ko oo UA o c CM CJ O vo CJ CJ ΙΛ ·< CM KA O O • · ua o UA » · VO Ο O UA CM I CM CJ UA ¢0 CJ CJ -rKA < o o CM CM O CM CM VO O CM KA CM O • · KA VO VO UA UA • · UA σ co KA r Ο £ O ua ua KA KA KA CJ KA x}· UA UA UA σ σ σ UA UA C- C— • * ο ο ο νο Ο ΚΑ ΚΑ UA VO UA UA σ σ «Τ“ Ο ΚΑ νο C— ΚΑ ΚΑ $ σ σ σ UA UA 1~ £— ’Φ Ο ο > ΚΑ Ο τUA UA σ σ I β ο ο ο d CM Φ Η ft »“Ι S' β ο φ Ο Ή β Ή Ο Ο ρ Ρ Ρ Η 03 β Ο Η ω •rf ο β & LTA 03 Ή Η ο «Η ο ι—ί Ο •Η XS Ρ g ο ο ο d φ rJ ft β ο •Η Ρ $ § Φ β Ρ ω -1144586 Table 2 - continued Φ -P (β • ra ko cn tn 2.8 o tn 2.0 OJ OJ ra ra ci R στ tn T- kO στ ,3 • • • • • ft CM O tn m Ol tn Ol O ra R R ^d- t* στ cn στ Φ ϋ • • • Pi § $ in ’d* OI ’P* tn H O • *H ra co O R co kO tn tn • • • • • □ co to kO te? OJ *Η O • ra H CiD co c- o tn o =L 3 « • * • • kO in OJ Ol OJ kO Cl 3 R R rf rf » H H d a o 0 » ra ra ra 3 | 9 3 p CQ rf R R ri P R 0 o -P -p R R 3 P P Φ Φ •ri *H ft ft Φ OP to tn z IS «* Λ OJ ’d· t- in ra o tn kO^ tn xl· tn kp tn φ P o· rO ri QD Φ 44 s P> Φ P SP Φ 1) rf tn R «Ρ · a t— xh in kO Φ •P a · cn kO x+ p· R rf D .0 tn σ» σ» «d O RSS ra tk ιω ΊΑ 1 Μ) ra in sf a in d q p H-rlCM H ‘3 © 1 « OtJ 3 amfi® p ra fi φ Ί H 3 . O r+ d d -P HJ Oft Hd o ft H-P rf O-P O 0 O-P ο β 0 M gD rf rf Η Φ Ρ HH O PO O P o oo 3 *ri-P *H O H-P’H O HO Pm S3 0+=-P S3 OP-Ρ B3tn The preparation examples which follow are intended to illustrate, but not to restrict, the preparation of the injectable injection formulations according to the invention.

Example 1 g of 96% pure ethyl alcohol and 64.08 g of water are initially introduced into a reaction vessel and the solids, that is to say, in this case, 5.00 g of Niclofolan (5,5'-dichloro2,2'-dihydroxy-3,5'-dinitrodiphenyl) and 7.5 g of N-methylglucamine, as well as 20 g of polyvinylpyrrolidone with a molecular weight of about 25,000, are then stirred in whilst stirring with a high-speed stirrer. The resulting solution is filtered, filled, into a container and sterilised under wdter.

A dark red solution with a pH value of 9.4 is obtained.

The viscosity of the solution is 100 cps (centipoises).

In Examples 2 to 5 which follow the individual components are added together as described in Example 1. The constituents contained in the individual examples were added together in the following amounts: Example 2 Niclofolan active compound 5.0 g Di-lysine base, 50% in water 10.0 g EVP 25 (molecular weight about 25,000) 20.0 g 96% pure alcohox 5.0 g water, pro inj. 64.7 g 104.7 g = 100 ml Dark red solution, pH 9.4, viscosity about 125 cps.

Example 3 Niclofolan active compound 5.0 g Dl-lyeine base,50% water 10.0 g PVP 17 (molecular weight about 11,500) 20.0 g Water, pro inj. 71.3 g 106.3 g = 100 ml 44380 Dark red solution, pH 9.2» viecoaity 18 ops.

Example 4 Niclofolan active compound 4.0 g N-methylglucamine 6.0 g PVT 25 (molecular weight about 25,000) 16.0 g 96% pure alcohol 10.0 g water, pro inj. 67.0 g 103.0 g = 100 ml Dark red solution, pH 9.7, viscosity 55 cps.

Example 5 Niclofolan active compound 5.0 g triethanolamine 15.0 g PVP 25 (molecular weight about 25,000) 17.5 g water, pro inj. 69.5 g 107.0 g Dark red solution, pH 8.8, viscosity 66 cps.

Claims (11)

1. CLAIMS:1. A liquid injectable formulation comprising, as active compound, 5,5’-dichloro-2,2 1 -dihydroxy-3,3'-dinitrodiphenyl f one or more physiologically tolerable bases, a polyvinylpyrrolidone and water.

2. A formulation according to claim 1 further comprising a water-miscible organic solvent.

3. A formulation according to claim 2 containing from 2 to 7 per cent by weight of the said active compound,from 2 to 20 per cent by weight of the polyvinylpyrrolidone^ from 55 to 80 per cent by weight of water^and from 5 to 20 per cent by weight of a water-miscible organic solvent.

4. A formulation according to claim 2 or claim 3 wherein the water-miscible organic solvent comprises a mono- or polyhydrie alcohol.

5. A formulation according to any one of claims 1 to 4 having a pH of from 8 to 10.

6. A formulation according to any one of claims 1 to 4 wherein the base comprises I- or D,l-arginine, 1- or D,I-lysine, methylglucamine, glucosamine, triethanolamine, 2-amino-2-hydroxymethyl-nropane-1,3-diol, Ν,Ν,Ν',N‘-tetratis-(2-hydroxy-propyl) -ethylenediamine or a polyether-tetrol based on ethylenediamine.

7. A liquid injectable formulation substantiallyM hereinbefore described in any one of Examples 1 to 6.

8. A process for the preparation of a formulation according to any one of claims 1 to 7 which comprises stirring from 2 to 7 per cent by weight of the Niclofolan active compound with from 55 to 80 per cent by weight of water, optionally with the addition of 5 to 20 per cent by weight of a water^miscible organic solvent, adding from 2 to 20 per cent bv weight of a physiologically suitable organic base and from 5 to 20 per cent by weight of a polyvinylpyrrolidone whilst stirring continuously, and sterlising the resulting solution.

9. A process for preparing a formulation according to any one of claims 1 to 8 substantially as hereinbefore described in Example 1

10. A formulation according to any one of claims 1 to 7 prepared by a process according to claim 8 or claim 9.

11. A process for combating liver fluke in non-human animals which comprises injecting the animal with a formulation accord ing to any one of claims 1 to 7 or 10.