STABLE TOPICAL VETERINARY COMPOSITION

The present invention relates to a stable veterinary composition and to a method of preparing thereof. More specifically, the invention discloses the stable veterinary antiparasitic composition comprising at least one macrocyclic lactone and its use as topical composition in treating, controlling and/or preventing of ectoparasite and endoparasite infections in warmblooded animals.

Background of the invention

Animals including domestic and farm animals are often susceptible to parasite infestations. In order to improve efficiency in animal handling there is a great need in efficient control of parasites in an animal and in prevention of any possible harmful effects on the treated animal.

The macrocyclic lactones such as for example avermectins and milbemycins and their derivatives are products of soil microorganisms belonging to the genus Streptomyces. The macrocyclic lactones have a potent, broad antiparasitic spectrum at low dose levels and can be used to treat infections of more than 300 species of endoparasites and ectoparasites in a wide range of hosts. The macrocyclic lactones are well absorbed when administered orally or parenterally while the pour-on and spot-on formulations exhibit greater variability. Regardless of the route of administration, macrocyclic lactones are extensively distributed throughout the body and concentrate particularly in adipose tissue.

Some of the avermectins in commercial use are ivermectin, abamectin, doramectin, eprinomectin, and selamectine and some of commercially available milbemycins are milbemycin oxime and moxidectin.

Selamectine with a chemical name 25-Cyclohexyl-4'-0-de(2,6-dideoxy-3-0-metyl-a-L- arabino-hexopyranosyl)-5-demetoxy-25-de(1 -methylpropyl)-22,23-dihydro-5-(hydroxyimino)- avermectin A1a (USAN) is a semi-synthetic compound of the avermectin class. Selamectine was first disclosed in PCT publication No W094/15944 as a potent 5-oximino monosaccharide for use as an antiparasitic agent, particularly for treatment of prophylaxis of flea infestations.

Selamectine paralyses and/or kills a wide range of invertebrate parasites through interference with their chloride channel conductance causing disruption of normal neurotransmission. This inhibits the electrical activity of nerve cells in nematodes and muscle cells in arthropods leading to their paralysis and/or death. Selamectine has adulticidal, ovicidal and larvicidal activity against fleas. The composition marketed as Revolution ^® and Stronghold ^® is indicated for the treatment and prevention of flea infestations, for the prevention of heartworm disease and for the treatment of ear mites in cats and dogs. Additionally, the composition is used for the treatment of biting lice infestations (Felicola subrostratus), for the treatment of adult roundworms (Toxocara cati) and for the treatment of adult intestinal hookworms (Ancylostoma tubaeforme) in cats and in dogs for the treatment of biting lice infestations (Trichodectes canis), for the treatment of sarcoptic mange (caused by Sarcoptes scabiei) and for the treatment of adult intestinal roundworms (Toxocara canis).

The marketed composition is disclosed in PCT publication No WO2000/030449 as composition comprising (a) about 0.1-50% w/v selamectine; (b) about 1-50% v/v a di (C _2- 4 glycol) mono (C _1-4 alkyl) ether; (c) an optional antioxidant; and (d) an optional skin acceptable volatile solvent q. s. v/v. Particularly preferred glycol ether is dipropylene glycol monomethyl ether (DPGMME). In the product information leaflet of the marketed composition it is disclosed that stiff hair, clumping of hair, hair discoloration, or a slight powdery residue may be observed at the treatment site in some animals.

Several antiparasitic compositions comprising more than one active substance from different chemical classes are known. The veterinary antiparasite composition disclosed in PCT publication No WO2017/017091 comprises three different active substances fipronil, selamectine and praziquantel in an acceptable pharmaceutical vehicle that are represented by some glycol derivatives. US patent No US6991801 describes a spot-on combination composition comprising at least one macrocyclic lactone and at least one compound selected from praziquantel, morantel and pyrantel, a thickening agent, a liquid carrier vehicle comprising a solvent which could be DPGMME and a co-solvent and a crystallization inhibitor. PCT publication No WO2015/147655 discloses anthelmintic formulation of at least one macrocyclic lactone and levamisole wherein both active substances are solubilised together in a solvent system comprising dimethyl sulfoxide (DMSO) and at least one humectant. The concentration of DMSO is approximately 50 to 80% by weight.

Several penetration enhancers have been described in the state of the art as being suitable for topical transfer of the active substance through the skin. It is well known that there is no universal penetration enhancer or vehicle that would be optimal for the delivery of all classes of topical drugs across the skin of all species. Selection of optimal vehicle for transdermal delivery of a drug requires a close match between the physical and chemical properties of the drug, vehicle and skin lipids of the particular animal.

DMSO, first synthesized in 1866, is used in a number of regulated products in human and veterinary medicine. DMSO is a highly polar aprotic substance knowing to enhance topical penetration of drugs owing to its ability to displace bound water from the stratum corneum. Literature describes the penetration enhancing activities of DMSO and its effectiveness as an excellent accelerator but this effect is concentration dependent. Increases in drug penetration have been reported with DMSO concentrations as low as 15%. However, as disclosed by A.C.Williams et al., Advanced Drug delivery Reviews 64 (2012) 128-137 and M.E.Lane, International Journal of Pharmaceutics 447 (2013) 12-21 the significant increase in permeability generally requires higher concentrations than 60%. At these relatively high concentrations DMSO can cause erythema and wheals of the stratum corneum and may denature some proteins. A further problem is the metabolite dimethyl sulphide produced from the solvent that produces a foul odour on the breath. On the other side DMSO has been shown to have bactericidal, bacteriostatic and fungistatic activity, anti-oxidative properties and it possesses mild to moderate neuroprotective effects.

Therefore, there is a need to prepare the stable veterinary antiparasitic composition comprising an antiparasitic active substance and DMSO present in such an amount that provides desirable penetration of the active substance through the skin and at the same time takes advantages of DMSO (such as bactericidal, bacteriostatic and fungistatic activity, anti- oxidative properties and neuroprotective effect) and at the same time minimizes the disadvantages of DMSO (such as erythema and wheals of the stratum corneum).

Accordingly, it was an object of the present invention to provide a stable topical veterinary composition which is a skin-non-irritating and environmentally friendly and which may also contribute to an analgesic activity, a swelling-reducing activity and/or an anti-inflammatory activity. In addition to that, there was a need for a composition which would not cause stiffness of hair, clumping of hair, hair discoloration and powdery residue at the site of application.

This objective is surprisingly achieved by the topical veterinary composition comprising at least one macrocyclic lactone, DMSO in an amount between 0.5-15% of the composition, an organic solvent and optionally an antioxidant. Preferred macrocyclic lactone is selamectine. The topical veterinary composition according to the present invention is used in treating, controlling and/or preventing of ectoparasite and endoparasite infections in warm-blooded animals.

Description of the invention

A first aspect of the present invention is directed to a stable topical veterinary composition comprising:

a) at least one macrocyclic lactone, preferably selamectine,

b) dimethyl sulfoxide (DMSO) in an amount between 0.5-15% w/v,

c) an organic solvent and

d) optionally an antioxidant.

According to one object or embodiment of the present invention the macrocyclic lactone may be selected from avermectins, milbemycins and any combinations thereof. The avermectin may be selected from the group consisting of ivermectin, abamectin, doramectin, cydectin, emamectin, eprinomectin and selamectine and milbemycin may be moxidectin and any combinations thereof. Preferably selamectine is used as the macrocyclic lactone.

According to another object or embodiment of the present invention a macrocyclic lactone is combined with another active substance suitable for veterinary application, such as active ingredients with parasiticidal activity selected from ectoparasiticides, endoparasiticide or endectocides. Ectoparasiticides can be selected form organochlorines, organophosphates, carbamates, amidines, synthetic pyrethroids, benzoylureas, juvenile hormone analogues, neonicotinoids, fhenylpyrazoles, spinosyns, isoxazolines. Endoparasiticides can be selected from benzimidazoles, imidazothiazoles, tetrahydropyrimidines, isoquinolines, salicylanilides.

Another object or embodiment of the present invention is a stable topical veterinary composition comprising:

a) selamectine,

b) DMSO in an amount between 0.5-15% w/v of the composition,

c) an organic solvent and

d) optionally an antioxidant.

There is provided a stable topical veterinary composition comprising:

a) selamectine,

b) DMSO in an amount between 0.5-15% wt. of the composition,

c) an organic solvent, and d) optionally an antioxidant.

The term "% wt. of the composition" can be used herein interchangeably with the term "% wt., based on the total weight of the topical veterinary composition". The term "DMSO in an amount between ... to ... % wt. of the composition" can be used herein interchangeably with the term "DMSO in an amount between ... to ... % wt., based on the total weight of the topical veterinary composition".

The organic solvent can be in particular an organic solvent other than DMSO.

Optionally, a topical veterinary composition of the present invention comprising selamectine may further comprise another active substance suitable for veterinary application, such as active ingredients with parasiticidal activity selected from ectoparasiticides, endoparasiticide or endectocides. Ectoparasiticides can be selected form organochlorines, organophosphates, carbamates, amidines, synthetic pyrethroids, benzoylureas, juvenile hormone analogues, neonicotinoids, phenylpyrazoles, spinosyns, isoxazolines. Endoparasiticides can be selected from benzimidazoles, imidazothiazoles, tetrahydropyrimidines, isoquinolines, salicylanilides.

Selamectine can be prepared by the routes of synthesis reported in the following references: US981500, EP677054, WO94015944, US6906184, EP1003764, WO99007721 , EP2835376 wherein selamectine is prepared from doramectine. Selamectine can be used in crystalline, amorphous form or in the form of solvates. The preferred form is amorphous form.

The median particle size of selamectin used for the preparation of the composition of the present invention can be less than 200 pm. The particle size can be determined by laser diffraction methods using instruments such as Mastersizer 2000.

Purity grade of selamectine used in the composition of the present invention can be above 90%, preferably above 95%, more preferably above 98% as determined by HPLC. Preferably the specification for limits of related compounds comply with Ph. Eur. monograph for selamectine (especially complies with Ph. Eur. monograph version in force 17.03.2017).

The amount of selamectine present in the composition according to the present invention can range from 0.5 to 30% w/v, preferably from 2 to 20% w/v, more preferably from 4 to 14% w/v, especially from 6 to 12% w/v. According to one embodiment, the amount of selamectine present in the composition according to the present invention can be 6 % w/v. According to another embodiment, the amount of selamectine present in the composition according to the present invention can be 12% w/v.

According to one object or embodiment of the present invention DMSO is present in the composition in an amount of 0.5 to 15% w/v, preferably in an amount of 2 to 14.5% w/v, more preferably in an amount of 4 to 14% w/v.

Ratio of selamectine to DMSO can range from 3 to 1 , preferably from 2 to 1 and more preferably from 1.5 to 1.

According to one object or embodiment of the present invention an organic solvent can be selected from the group consisting of alcohols, ethers, esters, ketones, such as acetone, ethyl acetate, methanol, ethanol, isopropanol, preferably alcohols such as isopropyl alcohol, ethanol, and more preferably isopropyl alcohol is used as an organic solvent.

Alcohols can be in particular alcohols of formula R ^a -OH, wherein R ^a can be selected from alkyls, especially can be selected from C1-C6 alkyls (e.g. can be selected from C1 alkyl, C2 alkyl, C3 alkyls, C4 alkyls, C5 alkyls), such as straight chain C1-C6 alkyls, and branched C3- C6 alkyls. Ethers can be in particular ethers of formula R ^b -0-R ^c , wherein R ^b , R ^c , can be each independently selected from alkyls, especially can be each independently selected from C1- C4 alkyls. Esters can be in particular esters of formula R ^d -C(0)-0-R ^e , wherein R ^d , R ^e , can be each independently selected from alkyls, especially can be each independently selected from C1-C4 alkyls. Ketones can be in particular ketones of formula R ^f -C(0)-R ⁹ , wherein R ^f , R ⁹ , can be each independently selected from alkyls, especially can be each independently selected from C1-C4 alkyls.

The term "w/v" means "weight/volume". "1% w/v" means 1 g in 100 ml of the topical veterinary composition. Weight and volume, especially volume of the topical veterinary composition, can be in particular determined at a temperature of 20°C, especially at a temperature of 20°C and at a pressure 101325 Pa.

The topical veterinary composition can be a fluid (especially at a temperature of 20°C, e.g. at a temperature of 20°C and at a pressure 101325 Pa). The topical veterinary composition can be a solution or suspension (especially at a temperature of 20°C, e.g. at a temperature of 20°C and at a pressure 101325 Pa), preferably a solution (especially at a temperature of 20°C, e.g. at a temperature of 20°C and at a pressure 101325 Pa). The amount of organic solvent present in the composition according to the present invention can range from 55% w/v to 99% w/v, preferably from 65% w/v to 95% w/v more preferably from 70% w/v to 90% w/v.

According to one object or embodiment of the present invention an antioxidant can be selected from the group consisting of butylated hydroxyanisole, butylated hydroxytoluene, tocopherols, ascorbic acid, sodium metabisulphite, propyl gallate, sodium thiosulphate or a mixture of not more than two of them, preferably butylated hydroxytoluene and butylated hydroxyanisole and more preferably butylated hydroxytoluene is used as an oxidant.

The amount of an antioxidant present in the composition according to the present invention can range from 0- 0.3% by weight, preferably 0.05-0.25% by weight, most preferably 0.05- 0.15% by weight.

The present invention pertains also to the following formulation embodiments:

The composition embodiment 1 of the present invention is a stable topical veterinary composition comprising:

a) 0.5 - 30 % w/v of selamectine,

b) 0.5 -15% w/v of DMSO

c) an organic solvent and

d) optionally an antioxidant.

In particular, the organic solvent can be an organic solvent other than DMSO. The organic solvent can be in particular selected from the group consisting of alcohols, ketones, ethers, esters, especially selected from the group of acetone, ethyl acetate, methanol, ethanol, and isopropanol.

The composition embodiment 2 of the present invention is a stable topical veterinary composition comprising:

a) 2 - 20 % w/v of selamectine,

b) 2 -14.5 % w/v of DMSO

c) an organic solvent and

d) optionally an antioxidant.

In particular, the organic solvent can be an organic solvent other than DMSO. The organic solvent can be in particular selected from the group consisting of alcohols, ketones, ethers, esters, especially selected from the group of acetone, ethyl acetate, methanol, ethanol, and isopropanol.

The composition embodiment 3 of the present invention is a stable topical veterinary composition comprising:

a) 4 - 14 % w/v of selamectine,

b) 4 -14 % w/v of DMSO

c) an organic solvent and

d) optionally an antioxidant.

In particular, the organic solvent can be an organic solvent other than DMSO. The organic solvent can be in particular selected from the group consisting of alcohols, ketones, ethers, esters, especially selected from the group of acetone, ethyl acetate, methanol, ethanol, and isopropanol.

The composition embodiment 4 characterised in that the composition embodiments 1 to 3 comprise isopropyl alcohol as an organic solvent.

The composition embodiment 5 of the present invention characterised in that is comprises a) 12 % w/v of selamectine,

b) 4 -14 % w/v of DMSO

c) isopropyl alcohol and

d) optionally an antioxidant.

The composition embodiment 6 of the present invention characterised in that is comprises a) 6 % w/v of selamectine,

b) 4 -14 % w/v of DMSO

c) isopropyl alcohol and

d) optionally an antioxidant.

The composition embodiment 7 of the present invention characterised in that it comprises a) 6 - 12 % w/v of selamectine,

b) 4 -14 % w/v of DMSO

c) isopropyl alcohol and

d) optionally an antioxidant. The composition embodiment 8 of the present invention is a stable topical veterinary composition comprising:

a) 0.5 - 30 % w/v of selamectine,

b) DMSO in an amount between 0.5-15% wt. of the composition,

c) an organic solvent and

d) optionally an antioxidant.

In particular, the organic solvent can be an organic solvent other than DMSO. The organic solvent can be in particular selected from the group consisting of alcohols, ketones, ethers, esters, especially selected from the group of acetone, ethyl acetate, methanol, ethanol, and isopropanol.

The composition embodiment 9 of the present invention is a stable topical veterinary composition comprising:

a) 2 - 20 % w/v of selamectine,

b) DMSO in an amount between 2 -14.5 % wt. of the composition,

c) an organic solvent and

d) optionally an antioxidant.

In particular, the organic solvent can be an organic solvent other than DMSO. The organic solvent can be in particular selected from the group consisting of alcohols, ketones, ethers, esters, especially selected from the group of acetone, ethyl acetate, methanol, ethanol, and isopropanol.

The composition embodiment 10 of the present invention is a stable topical veterinary composition comprising:

a) 4 - 14 % w/v of selamectine,

b) DMSO in an amount between 4 -14 % wt. of the composition,

c) an organic solvent and

d) optionally an antioxidant.

In particular, the organic solvent can be an organic solvent other than DMSO. The organic solvent can be in particular selected from the group consisting of alcohols, ketones, ethers, esters, especially selected from the group of acetone, ethyl acetate, methanol, ethanol, and isopropanol. The composition embodiment 11 characterised in that the composition embodiments 8 to 10 comprise isopropyl alcohol as an organic solvent.

The composition embodiment 12 of the present invention characterised in that it comprises a) 12 % w/v of selamectine,

b) DMSO in an amount between 4 -14 % wt. of the composition,

c) isopropyl alcohol and

d) optionally an antioxidant.

The composition embodiment 13 of the present invention characterised in that it comprises a) 6 % w/v of selamectine,

b) DMSO in an amount between 4 -14 % wt. of the composition,

c) isopropyl alcohol and

d) optionally an antioxidant.

The composition embodiment 14 of the present invention characterised in that it comprises a) 6 - 12 % w/v of selamectine,

b) DMSO in an amount between 4 -14 % wt. of the composition,

c) isopropyl alcohol and

d) optionally an antioxidant.

The composition according to the present invention may additionally comprise one or more veterinary acceptable excipients selected from the group consisting of co-solvents, stabilizers, anti-nucleating agents, crystallization inhibitor, spreading agents, systemic absorption agents and similar. A single excipient may have one or more functions.

Preferably, a composition according to the present invention, especially a spot-on composition according to the present invention, can be a fluid composition, in particular a liquid composition.

The composition according to the present invention can be administered at monthly intervals, particularly preferred is once monthly application.

The composition according to the present invention can be filled into containers for single dose application. Suitable containers are, for example, plastic tubes consisting of polypropylene, pipettes consisting of polypropylene or of a blister film (polypropylene/cyclic- olefin-copolymer/ polypropylene) and a foil lidstock (aluminium/polypropylene co-extruded). The tubes or pipettes may be sealed into secondary packaging such as clear PVC blister closed by heat sealing with aluminium foil, polychlorotrifluoroethylene PCTFE/PVC heat sealed blister packs or aluminium sachets in order to protect the formulation from moisture or evaporation. The composition of the present invention may be filled into primary packaging material and packed into secondary packaging under inert gas atmosphere. Optionally nitrogen or argon can be used as inert gas atmosphere in the packaging procedure, wherein nitrogen is especially preferred.

The compositions according to the invention can be prepared by conventional processes by mixing the active compounds under stirring with the other components and preparing a solution. The process according to the present invention comprises the following steps:

- adding organic solvent and optionally antioxidant into a mixer

- (optionally) adding other veterinary acceptable excipient(s) into solvent mixture under stirring until clear solution is obtained

- adding selamectine to the mixture under stirring until clear solution is obtained

- adding dimethyl sulfoxide to the mixture under stirring until clear solution is obtained.

The process is preferably carried out in an inert atmosphere, i.e. under flow of inert gas, such as nitrogen, argon, helium, neon, krypton, xenon, preferably nitrogen or argon, most preferably nitrogen.

Adding other veterinary acceptable excipient(s) can be in particular adding one or more veterinary acceptable excipients selected from the group consisting of co-solvents, stabilizers, anti-nucleating agents, crystallization inhibitor, spreading agents, and systemic absorption agents.

In particular, the process for preparing a composition of the present invention can comprise the following steps: a) adding organic solvent and optionally antioxidant into a mixer; b) (optionally) adding one or more other veterinary acceptable excipient(s) into solvent mixture (obtained after step a)) under stirring until clear solution is obtained, e.g. said one or more other veterinary acceptable excipients can be selected from the group consisting of coll solvents, stabilizers, anti-nucleating agents, crystallization inhibitor, spreading agents, and systemic absorption agents; c) adding selamectine to the mixture (obtained after step a) or after optional step b)) under stirring until clear solution is obtained; and d) adding dimethyl sulfoxide to the mixture (obtained after step c)) under stirring until clear solution is obtained.

According to another object or embodiment of the present invention the composition is applicable topically to the skin of animal in the form of liquid composition, preferably in the form of spot-on or pour-on composition, more preferably in the form of spot-on composition.

According to another object or aspect of the present invention the composition is used in treating, controlling and/or preventing of ectoparasite and endoparasite infections in warmblooded animals. More particularly, the composition is used in the treatment and prevention of flea infestations, for the prevention of heartworm disease, for the treatment of ear mites, for the treatment of biting lice infestations, for the treatment of adult roundworms, for the treatment of adult intestinal hookworms, for the treatment of biting lice infestations, for the treatment of sarcoptic mange and for the treatment of adult intestinal roundworms.

According to a further aspect of the present invention, a topical veterinary composition of the present invention is for use as a medicament.

According to a still further aspect of the present invention, a topical veterinary composition of the present invention can be for use as a medicament for treating, controlling and/or preventing of ectoparasite and endoparasite infections, especially in warm-blooded animals.

In particular, a topical veterinary composition of the present invention can be for use as a medicament for treating, and controlling ectoparasite and endoparasite infections, especially in warm-blooded animals. Furthermore, a topical veterinary composition as disclosed herein can be for use as a medicament for preventing ectoparasite and endoparasite infections, preferably in warm-blooded animals.

According to one object or embodiment of the present invention the treated warm-blooded animal can be selected from the group consisting of warm-blooded animals, such as e.g. household animals (especially pet animals) and laboratory animals, especially e.g. dogs, cats, hedgehogs, ferrets, horses, sheep, and rodents, such as gerbils, hamsters, chinchillas, fancy rats and guinea pigs, preferably dogs, cats, ferrets, guinea pigs, and more preferably dogs and cats.

By the composition of the present invention several problems has been solved.

The composition according to the present invention has shown surprisingly good cosmetic profile. During the in-vivo study significantly less stiffness and clamping of hair at the application site was observed for the composition of the present invention than for the reference product. White residue in the form of oily patches at the application site was observed in much lesser extent than for the reference product. This characteristic may be attributed to the fact that DMSO is rapidly absorbed skin penetrant and that it has the ability to carry active ingredients through membranes thereby provides for rapid absorption of active ingredients.

DMSO has anti-oxidative properties and provides for stabilization of the active ingredients against oxidative decomposition, such as selamectine, thus compositions according to present invention retain their therapeutic activity and their specific properties over a longer period of time. The inventors have shown that the composition according to present invention is surprisingly storage stable. Stability testing under accelerated conditions (40°C, 60% RH) has shown that the total content of related substances was not increased after several months of storage.

The above listed advantages provided by a composition of the present invention comprising DMSO may contribute to increasing the treatment acceptance of subjects (e.g. animals, especially pet and farm animals) treated with a composition of the present invention and the treatment acceptance of the care givers, e.g. pet owners, keepers in laboratories and animal shelters. An increased treatment acceptance of subjects will in turn largely facilitate the time- intensive work of treating subjects (e.g. pet animals) with a composition of the present invention for control of parasites. Treatment acceptance would encourage the care givers to treat animals on a regularly basis thus providing long term prevention against parasites.

The bioequivalence of the composition of the present invention with the marketed product has been shown in the in-vivo study.

In particular, the following items are provided by the present inventors:

1. A topical veterinary composition comprising:

a) selamectine, b) DMSO in an amount between 0.5-15% wt. of the composition,

c) an organic solvent and

d) optionally an antioxidant.

2. The topical veterinary composition according to item 1 comprising:

a) 0.5 - 30 % w/v of selamectine,

b) 0.5 -15% w/v of DMSO

c) an organic solvent and

d) optionally an antioxidant.

3. The topical veterinary composition according to item 2 comprising:

a) 2 - 20 % w/v of selamectine,

b) 2 -14.5 % w/v of DMSO

c) an organic solvent and

d) optionally an antioxidant.

4. The topical veterinary composition according to item 3 comprising:

a) 4 - 14 % w/v of selamectine,

b) 4 -14 % w/v of DMSO

c) an organic solvent and

d) optionally an antioxidant.

5. The topical veterinary composition according to any one of the preceding items characterised in that isopropyl alcohol is used as an organic solvent.

6. The topical veterinary composition according to any one of the preceding items characterised in that it comprises

a) 12 % w/v of selamectine,

b) 4 -14 % w/v of DMSO

c) isopropyl alcohol and

d) optionally an antioxidant.

7. The topical veterinary composition according to any one of the preceding items characterised in that it comprises

a) 6 % w/v of selamectine,

b) 4 -14 % w/v of DMSO

c) isopropyl alcohol and

d) optionally an antioxidant.

8. The topical veterinary composition according to any one of the preceding items characterised in that it is in the form suitable for spot-on application.

9. The topical veterinary composition according to any one of the preceding items characterised in that it is a fluid. 10. The topical veterinary composition according to any one of the preceding items characterised in that it is a solution or suspension.

11. The use of a topical veterinary composition according to any preceding item for use in treating, controlling and/or preventing of ectoparasite and endoparasite infections in warmblooded animals.

12. The topical veterinary composition according to any one of items 1 to 10 for use as a medicament.

13. The topical veterinary composition according to any one of items 1 to 10 for use as a medicament for treating, controlling and/or preventing of ectoparasite and endoparasite infections, especially in warm-blooded animals.

14. The topical veterinary composition according to item 13 for use as a medicament for treating, and controlling ectoparasite and endoparasite infections, especially in warmblooded animals.

15. The topical veterinary composition according to item 13 for use as a medicament for preventing ectoparasite and endoparasite infections, especially in warm-blooded animals.

The present invention is illustrated using the following non-limiting examples.

Examples

Example 1

12%w/v composition

Example 1a

Bioequivalence study

The formulation was tested in vivo bioequivalence study on dogs. The formulation was demonstrated to be bioequivalent to the reference STRONGHOLD® (Selamectine) 12% w/v Spot-on Solution for Dogs, since the Test to Reference ratio of geometric LS means as well as the corresponding 90% confidence interval for C _max and AUC ₀ - _t of selamectine were all within the acceptance range of 80.00 to 125.00%. Example 1b

Stability data:

The composition according to Example 1 was stable under room and accelerated stability testing conditions, which was shown in the following Table:

m - months

RH - relative humidity

The analytical method used for determining related substances of selamectine was a reversed-phase gradient HPLC method, using a 4 pm C18 column or a suitable alternative. The mobile phase was a combination of water and acetonitrile, with UV detection at 243 nm.

Example 2

6%w/v composition

Example 2a

Stability data:

The composition according to Example 2 was stable under room and accelerated stability testing conditions, which was shown in the following Table: Sample Testing condition Total Impurities (%)

6% w/v spot on to < 0.30%

solution 25°C/60% RH - 12m < 0.30%

40°C/75 % RH - 6m < 0.30% m - months

RH - relative humidity

The analytical method used for determining related substances of selamectine was a reversed-phase gradient HPLC method, using a 4 pm C18 column or suitable alternative. The mobile phase was a combination of water and acetonitrile, with UV detection at 243 nm.

Example 2b

Bioequivalence study

The formulation was tested in vivo bioequivalence study on cats. The formulation was demonstrated to be bioequivalent to the reference STRONGHOLD® (Selamectine) 6% w/v Spot-on Solution, since the Test to Reference ratio of geometric LS means as well as the corresponding 90% confidence interval for C _max and AUC ₀ - _t of selamectine were all within the acceptance range of 80.00 to 125.00%.