AU2015203871A1 - Veterinary Topical Formulation - Google Patents

Abstract

A stable pour-on formulation for cattle contains levamisole base and at least one active selected from the group of macrocyclic lactones, with the actives dissolved in a non-aqueous system 5 including one or more solvents selected from the group comprising dimethyl acetamide, dimethyl isosorbide, diethyl phthalate and dimethyl phthalate.

Description

VETERINARY FORMULATIONS FIELD OF THE INVENTION This invention relates to the field of veterinary pharmaceuticals and in particular to the 5 development of improved anthelmintic formulations containing a combination of active ingredients. BACKGROUND OF THE INVENTION The control of gastrointestinal parasites is an important aspect of modern livestock farming. 10 Typically these parasites are controlled by specific chemical agents developed to meet certain criteria. These criteria include: 1. High effectiveness against the target parasites - this could either be via broad spectrum efficacy in which a wide range of parasites are controlled or alternatively narrow spectrum of activity in which a more limited selection of parasites are controlled. 15 2. Wide margin of safety to the host animal 3, Low potential to cause toxic residues that could cause harm to humans consuming meat or milk products from the animal Over the past 50-60 years there have been 5 major classes of broad spectrum anthelmintic developed. These 5 classes are as follows: 20 Benzimidazoles. The first chemical class of modern anthelmintics developed was the benzimidazoles (BZD). The first drug in this class, thiabendazole (TBZ) was introduced in 1961. Other members of the benzimidazole class include fenbendazole, albendazole and oxfendazole. Benzimidazole based anthelmintics interfere with the worm's energy metabolism on a cellular 25 level. They bind to a specific building block called beta tubulin and prevent its incorporation into certain cellular structures called inicrotubules, which are essential for energy metabolism.

2 Interfering with energy metabolism is a much more basic mode of activity than that which occurs with other classes of anthelmintics, For this reason, benzimidazoles are also able to kill worm eggs. Benzimidazoles have a wide margin of safety and broad spectrum activity. Nicotinic agonists 5 Nicotinic agonists, comprise the next class of anthelmintics, They include imidazothiazoles and tetrahydropyrimidines. The imidazothiazole group includes levamisole, while the tetrahydropyrinidine group includes pyrantel pamoate, pyrantel tartrate, and morantel tartrate, The tetrahydropyrimidines mimic the activity of acetylcholine, a naturally occurring neurotransmitter that initiates muscular contraction. The worm is unable to feed and quickly 10 starves. Tetrahydroyrimidines only affect adult populations of worms. They do not have activity against the larval stages and are ineffective against cestodes (tapeworms) and trematodes (liver flukes). Inidazothiaoles have a similar mode of action causing spastic paralysis of the worms. The group includes the drug levanisole discovered in 1966. 15 Compared to other anthelmintics, levamisole has the narrowest margin of safety, though toxicity is usually the result of excess dosage. Levamisole has a broad spectrum of-activity and is effective against many larval stages of parasites, though not arrested larvae. Macrocyclic lactones The next anthelmintic class to be developed was the macrocyclic lactones (MLs) developed from 20 the same genus of soil dwelling-organisms (genus Streptomyces). The first drug of the class, ivermectin, was introduced in the early .1980s. Macrocyclic lactones consist of two closely related chemical groups: avermectins and milbemycins. The avermectins include abamectin, ivermectin doramectin and eprinomectin. The milbenycin group is represented by milbemycin oxime and moxidectin, introduced in 1997. 25 All of the macrocyclic lactone anthelmintics have the same mode of action. They interfere with GABA-mediated neurotransmission, causing paralysis and death of the parasite. Macrocyclic 3 lactones are the most potent killer of worms and are more persistent in their effect, The duration of persistent activity varies according to the drug and formulation. Macrocyclic lactones also have the unique quality of also killing several types of external parasite such as lice, mites, and Licks. They have a wide margin of safety for livestock and are effective 5 against all stages of worms, including inactive forms. Amino-acetonitrile derivatives In 2009 the first of this new class of anthelmintics was introduced. Monepantel acts by paralyzing worms by attacking a previously undiscovered receptor HCO-MPTL-1, present only in nematodes. Spiroindoles 10 In 2010 Derquantel (2- deoxoparaherquainide), the first of yet another new class of anthelmintic was introduced. All of the above anthelmintics have application in the control of a wide variety of ecto and endoparasites. Of particular concern are those parasites classified under the group of worms known as helminths. Helminthiasis is a prevalent and serious economic problem with domesticated 15 animals such as swine, sheep, horses, cattle, goats, dogs, cats and poultry, Among the Helminths, the group of worms described as nematodes cause widespread, and at times serious infection in various species of animals. Nematodes that are contemplated to be treated by the anthelmintics include, the following genera: 20 Acanthoche ilonema, Aelurosrrongylus, Ancylostoma, Angiostrongylus, Ascaridia, Ascaris, Brugia, Bunostomum, Capillaria, Chabertia, Cooperia, Crenosona, Dictyocaulus, Dioctophyme, Dipetalonema, Diphyllobothrium, Diplydium, Dirofilaria, Dracunculus, Enterobius, Filaroides, Haemonchus, Heterakis, Lagochilascaris, Loa, Mansonella, Muellerius, Nanophyetus, Necator, Nematodirus, Oesophagosromum, OpIsthorchis, Ostertagia, Oxyuris, Parafllaria,. Paragonimus, 25 Parascaris, Physaloptera, Protostrongylus, Setaria, Spirocerca, Spirometra, Stephanofilaria, Strongyloides, Strongylus, Thelazia, Toxascars, Toxocara, Trichinella, Trichonema, Trichostrongylus, Trichuris, Uncinaria, and Wuchereria. Of the above, the most common genera of nematodes infecting the animals referred to above are 4 Haemonchus, Trichostrongylus, Ostertagia, Nemaodirus, Cooperia, Ascars, Bunostomum Oesophagosomum, Chabertia, Trichuris, Strongylus, Trichonema, Dictyocaulus Capillaria, Heterakis, Toxocara, Ascaridia, Oxyuris, Ancylostoma, Unicinaria, Toxascaris and Parascaris. Certain of these, such as Nematodirus, Cooperia and Oesophagostornum attack primarily the 5 intestinal tract while others, such as Haemonchus and Ostertagia, are more prevalent in the stomach while others such as Diciyocaulus are found in the lungs, Still other parasites may be located in other tissues such as the heart and blood vessels, subcutaneous and lymphatic tissue and the like. While there have been many anthelmintics developed over the years of concern is the development 10 of resistance to anthelmintics belonging to the benzimidazole, nicotinic agonist and macrocyclic lactone classes and the high probability that it will similarly develop to anthelmintics from the more recently developed Amino-acetonitrile and spiroindole classes. Resistance refers to the process by which exposure of the parasite population to an anthelmintic leads to genetic selection of those parasites able to tolerate it, 15 While resistance can naturally be expected to occur at a certain rate the problem is exacerbated by over-exposure of the parasite population to the anthelmintic or by sub-lethal dosing of the parasite through. inaccurate-dose administration.. Of particular relevance to this application is the development of resistance to those classes of anthelmintic widely used in cattle. 20 Resistance to benzimidazole-based cattle drenches is widespread throughout the world. Cases have been reported that involve resistance in all three major cattle parasites species: Ostertagia, Trichostrongylus and Cooperia. Resistance to the nicotinic agonist derivative class (levamisole/morantel) is well known but is less widespread than benzimidazole resistance, 25 Resistance to the more recent macrocyclic lactone class is also becoming much more common, This is particularly troublesome given that it is by far the most popular form of parasite treatment for farmed cattle, 5 To prevent and manage the problem of anthelmintic resistance farmers have relied on various strategies including: 1. minimizing anthelmintic use by only treating at strategically important times 2. alternating the type of anthelmintic used 5 3. using combinations of anthelmintics from different classes to reduce the potential of parasites to survive the treatment. This patent application describes practical solutions to aid farmers in the application of the third strategy by providing an improved ready to use combination of anthelmintics selected from two different anthelmintic classes. 10 From the perspective of ease of administration it is most desirable that any combination is able to be applied topically. It would also be desirable that the formulation contained both a macrocyclic lactone active ingredient and levamisole, as both of these anthelmintics are used topically in cattle and such a combination would help ensure the widest spectrum of activity. It would further be desirable that a combination solution of macrocyclic lactone and levamisole 15 could be applied to the back of an animal in a form that would have a minimal tendency to run off the back of the animal before absorption had occurred. DEFINITIONS The formulations of the present invention must be stable to be of commercial use. In this 20 specification, a commercially acceptable anthelmintic formulation is one which is stable at room temperature for a period of at least 3 months. In conditions of accelerated testing, at 40' C., this requires the potency of the actives within the formulation to remain within specified and acceptable limits for 6 weeks. Where used in this specification macrocyclic lactone anthelmintics refer to a class of active 25 ingredients having anthelmintic activity, The macrocyclic lactone class includes by way of example; abamectin, ivermectin, dorameotin, eprinomectin and moxidectin.

6 Levamisole used in this specification includes levamisole hydrochloride, levamisole base, levamisole phosphate together with other salts and forms. It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless 5 otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process, 10 PRIOR REFERENCES All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents, It will be clearly understood that, 15 although a number of prior art publications may be referred to herein; this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country. NZ 336139 (Novartis) represents a recent attempt to formulate a combination product containing a macrocyclic lactone anthelmintic and levamisole. 20 Based on emulsion technology, the formulation described includes levamisole in an aqueous acidic phase and macrocyclic lactone in a lipophilic phase. A third active could potentially be suspended in particulate form in the aqueous phase, The disadvantage of this formulation is the need for the formulation to be shaken or agitated into an emulsion. In addition, the product is chemically complicated including 2 or 3 different phases. 25 The complicated nature of the formulation in NZ 336139 is due in part to the different formulation requirements of the actives. Macrocyclic lactone active ingredients are substantially insoluble in water whereas levamisole is water soluble. Macrocyclic lactone active ingredients are most stable at a pH of about 6.6 while levamisole is most stable at a pH of less than about 4.

7 As will be appreciated, in addition to the need to be physically stable during storage, topical formulations also need to be safe to administer to the surface of the skin so that they do not cause excessive skin irritation. A more recent attempt to provide a stable formulation of a macrocyclic lactone anthelmintic 5 combined with levamisole is suggested in NZ520295 (Merial). In this patent a pyrrolidone solvent (N methyl pyrrolidone) was used to dissolve both active ingredients, This resulted in a fonnulation that was simple to prepare and demonstrated much improved stability of the two actives. Yet another attempted solution is suggested in NZ552040 (Bomac). In the proposed formulation the macrocyclic lactone and levamisole active ingredients are solubilized in a combination of a 10 glyceryl acetate solvent (triacetin) and glycerol formal, However this formulation does not offer improvement in shelf stability when compared to the prior art and the data presented in the patent indicates that it is potentially more poorly absorbed when compared to the formulation described in NZ520295. Most of these solvent selections are unsuitable for combinations of macrocylic lactones and 15 levamisole, either because they do not promote long terms stability of the formulation or because their presence in the formulation would promote severe skin site reactions on treated animals. Despite the various advancements stability has still been a limiting factor to widespread availability of Macrocyclic lactone/levamisole combination pour-on formulations. An additional problem with the proposed formulations is that they tend to have relatively low rates 20 of transdermal absorption. This is likely due to the fact that the solvents used have been selected primarily on the basis of minimizing degradation of the active ingredients during storage rather than due to their ability to transdermally deliver both actives. An additional aspect of current combination topical formulations is that they have a tendency to quickly run from the back of the animal. This is primarily due to the fact that such formulations are 25 largely or completely organic solvent based and therefore have the typically low viscosity of the solvent mix. In some instances the presently available formulations can be observed running completely down the side of the animal from their application point along the backline. This is a particular issue in cattle breeds with smooth shiny coats which offer no inherent barrier to formulation run-off.

8 Accordingly, there remains a need for a stable topical formulation containing a macrocylic lactone anthelmintic and levamisole, and that promotes improved transdermal absorption of the two anthelmintic active ingredients as well as reduced tendency for run-off. 5 OBJECT OF INVENTION It is an object of the present invention to provide an improved shelf stable anthelmintic combination formulation for topical administration to cattle, or one that will at least provide the public with a useful choice, 10 STATEMENT OF INVENTION In one aspect the invention relates to a stable formulation suitable for topical administration to animals including at least two anthelmintics wherein a first of the anthelmintics is selected from the macrocyclic lactone class and the second of said anthelmintics is levamisole; said actives being dissolved in a non-aqueous solvent system including one or more solvents selected from the group 15 comprising dimethyl acetamide, dimethyl isosorbide and diethyl phthalate. Preferably the macrocyclic lactone anthelmintic is selected from the group including abamectin, doramectin, eprinomectin, ivermectin and moxidectin, More preferably the macrocyclic lactone anthelmintic is present in the range of between 0.01 - 5% w/v. 20 Preferably levamisole is present in the range of between 1 - 30% w/v. Preferably the formulation additionally includes at least one further medicament selected from the group comprising anthelinintics, dietary supplements, and vitamins, mineral and other beneficial agents. More preferably wherein the formulation additionally includes excipients including preservatives, 25 stabilisers, flavorants, co solvents. Preferably the formulation is suitable for topical administration.

9 More preferably the formulation does not cause unacceptable levels of skin irritancy when applied topically. In a furthei- aspect the invention relates to macrocyclic lactone/levamisole combination topical formulations in which the solvent system contains a viscosity modifying agent designed to 5 minimize run-off of the formulation from the back of the animal. In a further aspect the invention relates to macrocyclic lactone/levamisole combination topical formulations which further include triclabendazole. In a further aspect the invention relates to a method of manufacturing a veterinary topical formulation containing a levarnisole active ingredient and at least one macrocyclic lactone active 10 ingredient. In a yet further related aspect the invention relates to a method of treating or preventing infection of cattle with Cooperfa or Ostertagia by administering a formulation of the present invention. DESCRIPTION A series of studies were undertaken in an attempt to improve on the shelf stability of currently 15 available macrocyclic lactone/levamisole topical formulations. In these studies abamectin was used as the representative macrocyclic lactone active, whilst levamisole, in its base form, was used as the representative levamisole anthelmintic. Solvent Selection A solvent selection process was initiated to determine which solvents might be suitable for 20 inclusion in a series of stability studies. All oily solvents were rejected based on previous knowledge of potential irritancy when combined with levamisole. A selected series of topical solvents were tested to determine their basic ability to offer improvements from those currently used as the main solvents in the commercially available Macrocyclic lactone/nicotinic agonist combination topical formulations (ECLIPSE@Merial, 25 SATURN@Bayer). In the trials formulations were prepared containing I% abamectin, 20% levamisole base and 0.1% BHT with all materials dissolved in the selected solvent.

10 Solvent ABA% ABA% % Comments @ 4 0 C @ 56 0 C difference 3 weeks -Methyl-2-pyrrolidino 1.09 0.9 -17.4% 1.1 Ig abarnectin added, Rapidly dissolved. Levamisole also rapidly dissolved. Glycerol 0.99 0.79 -20.2% Partial freezing of solution. After gentle triacetate warming one of the components had crystallized out of solution. I Og abamectin added. Took 90 minutes to dissolve. Levamisole took 20 minutes to dissolve. Dimethyl 1.09 0.74 -32.1% Abamectin solvent had frozen. After gentle sulfoxide warming sample was liquid. 120g abamectin added. Both abamectin and levamisole rapidly dissolved. N, 1.31 1.06 -19.0% 1.24g abamectin added. Both abamectin N-Dimethylacetamide and levamisole rapidly dissolved, Ethylene glycol 0,51 0.11 -784% Thin layer of precipitate on bottom of vial, Could not be mobilized by shaking or warming. L,20g abamectin added, Took 45 minutes to dissolve. Levamisole took 25 minutes to dissolve. Diethyl phthalate 1.06 0.84 -20.7% -1.16g abamectin added. Took 40 minutes to dissolve. Levamisole took 40 minutes to dissolve. Tetraethylene glycol 0.98 0.43 -56.1% 1.1Ig abamectin added. Took 20 minutes to dissolve, Levamisole took 10 minutes to dissolve. Solketal 1.08 0.69 -36.1% 1 12g abamectin added, Took 5 minutes to dissolve. Levamisole took 10 minutes to dissolve. Dimethyl isosorbide 0.97 0.84 -13.4% 1.15g abamectin added. Rapidly dissolved. Levamisole also rapidly dissolved. Ethyl L-lactate 0.96 0.42 -56.2% 1. 15g abamectin added, Took 5 minutes to dissolve. Levamisole dissolved (time taken not recorded). 2-Propanol 1,32 0.62 -53.0% 1.14g abamectin added. Took less than 5 minutes to dissolve, Levamisole took 5 minutes to dissolve, N, 1,19 0.8 -32.7% l.15g abamectin added. Took less than 5 N-Dimethylformamide minutes to dissolve, Levamisole took 10 minutes to dissolve, Butyl carbitol (DGBE) 1.13 0.62 -45.1% 1.13g abamectin added, Took 10 minutes to dissolve. Levamisole took 15 minutes to dissolve.

11 As might be expected the two solvents used in the marketed products, ECLIPSE@ and SATURN@ performed better than most of the other solvents tested. Surprisingly however three other solvents performed equally well, One in particular, Dimethyl isosorbido, performed best of all in terms of enhancing the stability of abamectin. 5 In order of performance: 1. Dimethyl isosorbide 13.4% 2. N-methyl pyrrolidone 17.4% 3. Dimethyl acetamide 19.0% 4. Glycerol acetate 20.2% 5. Diethyl phthlate 20.7% Surprisingly and quite unexpectedly the best solvents for stability of the macrocylic lactone active ingredient also were the easiest in which to dissolve the ingredients. Such a result indicates potential major advantages in processing simplicity and efficiency; Particularly as no heating is required to ensure a good solution is obtained. 10 Based on these results the five preferred samples were then tested for stability enhancement of the levamisole active ingredient. Data indicated that in the case of the preferred solvents the levamisole was more stable than the abamectin ingredient While it would appear that it would be most beneficial that dimethyl isosorbide alone be used in the 15 formulation unfortunately it is a very expensive solvent. For this reason a less expensive co-solvent would be desirable. The choice of dimethyl acetanide and diethyl phthalate offer advantages in terms of potential cost reduction. Further high temperature stress testing was conducted to determine whether a blend of solvents selected from the preferred solvents might offer cost savings without unacceptably compromising 20 the stability of the active ingredients. A number of samples were prepared containing abamectin, levamisole base, from 40 to 60% Dimethyl isosorbide and Dimethyl acetamide. These were then subjected to long-term storage of 55 0 C. Over the period of storage the abamectin potency of all sample replicates reduced by 12 between 15.6% and 19.4%, This demonstrated that the co-solvent system could meet the objective of cost saving while maintaining stability to at least the standard set with the group of preferred solvents. w/v% AL02-1 AL02-1 AL02-12 AL02-13 AL02-1 AL02-15 AL02-1 AL02-1 AL02-18 Abamectin 1% 1% 1% 1% 1% 1% 1% 1% 1% Levamisole base 20% 20% 20% 20% 20% 20% 20% 20% 20% Vehicle DM1 40 DM1 50 DM1 60% DM1 40*A DMI 50' DM 60*/ DMI 40' DM 50 DM 600 & & & & & & & & & DMA to DMA to DMA to DMA to DMA to DMA to DMA to DMA to DMA to 100ml 100ml 100ml 100mI 00ml IOOm] I00ml 100mI 100ml 4 0 C 1.53 0.97 1,02 0.98 0.98 0.98 1.02 1.01 0.92 55 0 C 1.29 0.8 0.83 0.79 0.82 0.81 0.84 0.9 0.75 %difference -15.69 -17.53 -18.63 -19.39 -16.33 -17.35 -17.65 -10.89 -18,48 5 Additional tests were then performed in which Dimethyl Isosorbide/Dimethyl Acetamide solutions were tested against Dimethyl Isorbide/Diethylene glycol monobutyl ether solutions containing 1% abamectin and 20% levamisole base. Results for accelerated testing at 55*C for 7 days indicated that for all batches there was a slight but completely unexpected improvement in abamectin stability for the Dimethyl Isosorbide/ Diethylene glycol nonobutyl ether solvent combination. 10 Use of Diethylene glycol monobutyl ether as a co-solvent would have the additional benefit of reducing the flash point of the formulation. Preferred Einbodiments In the preferred embodiments the formulations of the invention include a macrocyclic lactone active ingredient in combination with levamisole in a solvent system including one or more 15 solvents selected from the group comprising dimethyl acetamide, dimethyl isosorbide, dimethyl phthalate and diethyl phthalate. The following examples are provided as examples only and are in no way intended to limit the spirit or scope of the invention. Example Formulations 20 The formulations of the present invention can be prepared as follows: 13 1. To a mixing vessel add levainisole base and the macrocyclic lactone active ingredient in a quantity of the solvent system made up of one or more solvents selected from dimethyl acetamide, dimethyl isosorbide, diemethyl phthalate and diethyl phthalate, 2. Stir at room temperature until the actives have completely dissolved, 5 3. Add the remainder of the solvent/s or co-solvents as well as viscosity modifying agents to bring to volume and mix well until a clear solution is obtained. The formulation is also highly flexible in that the solvents and active ingredients can be added in any order. One or both active ingredients can be added to one solvent, while the second active ingredient could be subsequently added to the solution either before or after the addition of one or 10 more co-solvents Examples of topically applied formulations of the invention include: Formulation 1,0 Ingredient % w/ Abamectin 1% Levamisole Base 20% -DimetbyJ actamide_ .qv. Formulation 1.1 Ingredient % w/V Ivermectin 0.5% Levamisole Base 10% Dimethyl isosorbide q.v. 15 Formulation 1.2 Ingredient % w/v Eprinomectin 1.0% Levamisole Base 20% Diethyl phathlate q.v.

14 Formulation 1.3 Ingredient % w/v Moxidectin 0.5/ Levarnisole Base 10% Dimethyl isosorbide q.v. Formulation 14 Ingredient % w/v Ivermectin 0.5% Levarnisole Base 10% Dimethyl acetamide qv. 5 Formulation 1,5 Ingredient % w/v Doramectin 0.5% Levamisole Base 10% Dimethyl isosorbide 35%. Dimethyl acetanide q.v. 10 Formulation 1,6 Ingredient % W/v Doramectin 0.5% Levamisole Base 10% Dimethyl isosorbide 35%, Dimethyl acetamide q.v. 15 15 Formulation L,7 Ingredient %w/v Abamectin 1 .0% Levarnisole Base 20% Dinmethyl acetarnide 35%. -Diethyl pht halate q. Formulation I1.8 Jugreient% W/li Abamectin 0.5% 5 Le-vamnisole Base 10% Dimnethyl isosorbide 35%. DpItthy] phthalate, ___qv. Formulation 1,.9 Ingredient% l Ivermectin vs x Levarnisole Base 10% Dimethy acetamide 50%.

Dimethyl isosorbide g~v Formulation 2,0 Ingredient % wI'v Ivermectin 0.5% LeaiisleBase 10% Dimethyl isosorbide 50%. Dirnethyl aeamde -qv 16 Formulation 2.1 Ingredient % w/v Ivermectin 0.5% Levamisole Base 10% Diinethyl isosorbide 50%. Diethylene glycol mono[ q.v. ether Formulation 2.2 Ingredient % w/v Abamectin 1.0% Levamisole Base 20% Dimethyl isosorbide 30%. Diethylene glycol monot q.v. ether Formulation 2.3 Ingredient % w/v oxidectin 0.5% Levamisole Base 10% Dimethyl isosorbide 40%. Diethylene glycol mono qv. ether Formulation 2.4 Ingredient % w/v Iverm-ectin 0.5% Levamisole Base FO0%/ Dimethyl isosorbid e 40%. Dimnethl acetamide 25% Diethylene glycol monoi -q- 2 ether 17 Also, surprisingly during the experiments it was found that it was possible to solubilise triclabendazole within the same formulation as the macrocyclic lactone and levamisole. Various loadings of triclabendazole were successfully trialed with various combinations of the solvents. Stress testing of samples held at 55"C for 3 weeks also confirmed that adding triclabendazole 5 would result in a similar shelf life to that of the commercially available ECLIPSE@ Pour-On formulation. Test results were: 55 0 C for 3 weeks % Abainectin % Levainisole remaining remaining ECLIPSE Pour-On 71.17 98.20 0.5% Abamectin/10% Levamisole base/20% 69.79 84,24 Triclabendazole* in DMI 40%/DMA to vol. 0.5% Abamectin/10% Levamisole base/20% 72.45 96.49 Triclabendazole* in DMI 50%/DMA to vol The administration rates for topical administration of these formulations are generally in the order of 1 ml per 10 kg or I ml per 20 kg. 10 A particularly preferred formulation incorporates a combination of dimethyl isosorbide and dimethyl acetamide or Diethylene glycol monobutyl ether at a ratio of around 80/20 to 20/80. Various combinations of the preferred invention were then applied to test animals. In no case was there any apparent skin reaction to the formulations, Long-term stability testing of 3 batches of the preferred dimethyl isosorbide/diethylene glycol 15 monobutyl ether formulation demonstrated that the active ingredients remained well within their proposed limits; Test conditions were 25*C/60%R.H. Time in months B/N 0 3 6 Abamectin Levamisole Abarnectin Levamisole Abamectin Levamisole AL02-IP 1.07 20.67 1.06 20,77 1.07 20.34 AL02-2P 1.05 20.33 1.05 20.59 1.06 20.53 AL02-3P 1.06 20.49 1.05 20.44 1.07 20.21 18 A second aspect of the invention is the addition of one or more viscosity modifying agents to solvent based topical macrocyclic lactone/levamisole formulation systems. A number of such agents have been tested and found to be suitable for this application at levels low enough that they 5 have no discernible influence on the shelf-life stability of the formulation. Of particular usefulness are: Polymers- including Linear, Branched or Cross-linked polymers, Acrylic Polymers, Cross linked Acrylic Polymers - examples include:- Polyvinyl Pyrrolidone, Polyethylene, Polyethylene Wax, Polyethylene Glycols, PVM / MA capric diene cross-linked polymer (polyethylene methyl 10 ether / acrylic acid Methyl decanoate diene cross-linked polymer), poly vinyl PEG-n (n = 5M, 9M, 23M, 45M, 90M, 160M) and other, polyacrylic acid acrylate/CIO-30 alkyl acrylate cross-linked polymer, acrylate / bexadecyl ethoxy (20), itaconic acid ester copolymer, acrylate / hexadecyl ethoxy (20) methyl acrylate copolymer, acrylate / alkyl ethoxy fourteen (25) acrylate copolymer, acrylate / stearyl ethoxy (20), itaconic acid ester copolymer, acrylic ester ester / stearyl ethoxy (20) 15 methyl acrylate copolymer, acrylic / eighth Alkyl ethoxy (50) acrylate copolymer, acrylate / VA cross-linked polymer, PAA (polyacrylic acid), sodium acrylate /vinyl isodecyl ester cross-linked polymer, Carbomer (polyacrylic acid) and its sodium salt and other, silicone based polymers. Cellulose & Cellulose derivatives - examples include cellulose, cellulose gum, Microcrystalline 20 Cellulose, Carboxymethylcellulose Sodium, Hydroxyethylcellulose, Hydroxypropylcellu lose, Methylcellulose, cetyl hydroxyethyl cellulose, ethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, carboxymethyl cellulose, cellulose acetate butyrate, cellulose phthalate, cellulose acetate propionate, 25 Organoclays - examples include Bentonite, Attapulgite Oligomers - examples include Paraffin Wax Metallic sterates/isostearates/myristates/laurates/palmitates 30 19 Inorganic polymer and its modified silicate materials - examples include magnesium, silica, fumed silicas, sodium magnesium silicate, hydrated silica, montmorillonite, sodium magnesium lithium silicate, pyroxene, stearin ammonium montmorillonite, stearic ammonia water pyroxerie, quaternary ammonium -90 montmorillonite, quaternary ammonium montmorillonite -18, -18 5 quaternary ammonium water pyroxene Natural Waxes - examples include Beeswax, Carnoba wax, shellac Glycerides - examples include Glyceryl dibehenate, glycerol behenate. To test the effectiveness of the preferred materials a variety of topical formulations were tested, both including and excluding the viscosity modifying agent. A laboratory simulation was 10 undertaken using a substrate mounted on an inclined board, Various samples were then poured on to the top portion of the board with measurements taken as to how far down the board each formulation would run. The formulations tested included the following solvent/co-solvent combinations containing 1% abarneotin and 20% levamisole base both with and without the viscosity modifying agents: 15 Dimethyl isorbide 5O%/Diethylene glycol monobutyl ether q.v Dimethyl isosorbide 50%/Dimethyl acetamide q.v. N-Methyl pyrollidone 50%/ Diethylene glycol monobutyl ether q.v Triacetin 50% / Glycerol formal q.v. Of particular usefulness in the formulation were viscosity modifiers comprised of polyvinyl 20 pyrollidone and/or cellulose acetate butyrate, In all cases the addition of the viscosity modifier resulted in a considerable reduction in the tendency of the formulation to run. Typically formulations in which the material was added (at levels from 2-5%) resulted in a reduction in run length on the inclined board of between 50-70%. 25 ADVANTAGES 20 The invention the subject of the present application is advantageous as it provides stable formulations including a macrocyclic lactone anthelmintic in combination with levamisole. Further, the formulations retain each active in solution. The formulations are monophasic and suitable to manufacture on a commercial scale. In addition, 5 as both actives are in solution the formulations are physically stable in that it does not separate out into separate phases; either aqueous and lipophilic phases or liquid and solid phases. This enables the formulations that are the subject of this application to be used without requiring agitation or shaking before use and greatly reduces the risk of differing concentrations of actives through the drum or other storage container. 10 In addition, as the formulation excludes water the issue of incompatible pH requirements is alleviated, VARIATIONS Although a number of macrocyclic lactone (ML) anthelmintics have been described in the 15 examples it will be appreciated that other MLs may be used in place of those described. Similarly although levamisole base has been used in the examples it will be appreciated that other forms of levamisole may be used, It will of course be realized that while the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to 20 persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is hereinbefore described,

Claims (15)

1. 2. A formulation as claimed in claim I in which one or more solvents selected from dimethyl acetamide, dimethyl isosorbide, diethyl phthalate and dimethyl phthalate are present at a level of 10 from 20% to 85% w/v.
2. 3. A formulation as claimed in any one of the above claims in which the levamisole active ingredient and the at least one macrocyclic lactone active ingredient are dissolved in a system including a blend of dimethyl isosorbide and a second solvent selected from dimethyl acetamide, diethyl phthalate, dimethyl phthalate and glycol ethers. 15 4. A formulation as claimed in any one of the above claims which additionally includes at least one co-solvent selected from the chemical groups comprising glyceryl acetates, pyrollidones, glycol ethers, glycol esters, glycerol formal, and alcohols.
3. 5. A formulation as claimed in any one of the above claims, wherein the at least one macrocyclic lactone active ingredient is selected from the group comprising abamectin, ivermectin, 20 doramectin, eprinomectin, moxidectin, selamectin.
4. 6. A formulation as claimed in any one of the above claims wherein the at least one macrocyclic lactone active ingredient and the levamisole active ingredient remain within 10% of their initial specification for at least 3 months when stored at 254C or below and at ambient humidity. 25 7. A formulation as claimed in any one of the above claims, wherein the macrocyclic lactone active ingredient is present in the range of between 0.01-5% w/v. 22
5. 8. A formulation as claimed in any one of the above claims, wherein the levamisole active ingredient is in the base, hydrochloride or phosphate form.
6. 9. A formulation as claimed in any one of the above claims, wherein the levamisole active ingredient is in the base form. 5 10, A formulation as claimed in any one of the above claims wherein the levamisole active ingredient is present in the range of between 1-30% w/v.
7. 11. A formulation as claimed in any one of the above claims wherein the formulation additionally includes an additional anthelmintic selected from: benzinidazoles (including albendazole, fenbendazole, mebendazole, oxfendazole, oxibendazole, triclabendazole), clorsulon, 10 closantel, derquantel, febantel, monepantel, morantel, netobimin, nitroxynil, oxyclozanide, praziquantel, pyrantel and rafoxinide, 12, A formulation as claimed in any one of the above claims which includes a macrocyclic [actone, levamisole and triclabendazole at a concentration of from 5 to 50%
8. 13. A formulation as claimed in any one of the above claims wherein the formulations 15 additionally include antioxidants and/or stabilizers.
9. 14. A formulation as claimed in any one of the above claims wherein the formulation additionally includes at least one further medicament selected from the group comprising anthelmintics, dietary supplements, vitamins, mineral and other beneficial agents.
10. 15. A method of treating or preventing infection of cattle with Cooperia or Ostertagia by 20 administering a formulation as claimed in any one of claims 1 to 14.
11. 16. A method of preparing a formulation containing a levamisole active ingredient and at least one macrocyclic lactone active ingredient by the steps of: (a) Dissolving at least one of either the levamisole active ingredient or the macrocyclic lactone active ingredient in at least one solvent selected from dimethyl isosorbide, dimethyl 25 acetamide, diethyl phthalate and dimethyl phthalate (b) Adding a co-solvent or co-solvents if desired, and then the second active ingredient if not already dissolved in the solution, 23
12. 17. A method of preparing a formulation containing a levamisole active ingredient and at least one macrocyclic lactone active ingredient by the steps of: (a) Dissolving at least one of either the levamisole active ingredient or the macrocyclic 5 lactone active ingredient in at least one solvent selected from the chemical groups comprising glyceryl acetates, pyrollidones, glycol ethers, glycol esters, glycerol formal, and alcohols. (b) Adding a co-solvent or co-solvents selected from dimethyl isosorbide, dimethyl acetamide, diethyl phthalate and dimethyl phthalate 10 (c) Adding the second active ingredient if not already dissolved in the solution
13. 18. A method of preparing a formulation as claimed in claim 16 or 17 in which further medicaments, antioxidants, viscosity modifiers or stabilizers are added at any time.
14. 19. A solvent based topical formulation containing a macrocyclic lactone and a levamisole active ingredient dissolved in one or more organic solvents which further contain a viscosity 15 modifier designed to increase the viscosity of the formulation.
15. 20. A formulation according to claim 19 in which the viscosity modifier is added at a rate of less than 10%w/v 21, A formulation according to claim 19-20 in which the viscosity modifier is selected from the group comprising ppolymers(including Linear, Branched or Cross-linked polymers, Acrylic 20 Polymers, Cross-linked Acrylic Polymers), Cellulose & Cellulose derivatives, Organoclays, Oligomer,Aluminum stearates/isostearates/myristates/laurates/palmitates, inorganic polymer and its modified silicate materials, natural waxes and glycerides. 22, A stable formulation suitable for topical administration to cattle substantially as herein described with reference to any one of the examples.