NZ535644A - Anthelmintic formulations - Google Patents

Abstract

Disclosed is a stable pour-on veterinary formulation suitable for administration to animals containing at least two different anthelmintic actives, the first active being levamisole base and the second active being abamectin, wherein both actives are dissolved in a solvent system comprising n-methyl-2-pyrrolidone and diethylene glycol n-butyl ether.

Description

New Zealand Paient Spedficaiion for Paient Number 535644 535 6 4 4 Patents Form # 5 DIVISIONAL OUT OF APPLICATION #520295 ANTE-DATING REQUESTED TO 19 JULY 2002 NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION Title ANTHELMINTIC FORMULA TIONS We, ASHMONT HOLDINGS LIMITED Address: First Floor, 17 Shea Terrace, Takapuna, Auckland, New Zealand Nationality: A New Zealand company do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: 00W771NZA_UP_Divpat_23Sep2004_001 doc FEE CODE - 1050 2 FIELD OF THE INVENTION This invention relates to the field of veterinary pharmaceuticals and in particular to anthelmintic formulations including a combination of actives.

BACKGROUND Anthelmintics are an important tool for farmers seeking to improve the productivity of grazing cattle. The first class of modern broad-spectrum anthelmintic was the benzimidazoles introduced in the early 1960's, followed by levamisole and morantel in the late 1960's and finally the avermectins and milbemycins in the early 1980's.

Anthelmintic Year of Introduction Main Active's in the Group Benzimidazoles Early 1960's Thiabendazole, albendazole, fenbendazole, oxfendazole Levamisole/Morantel Late 1960's Levamisole, morantel Avermectins/Milbemycin s Early 1980's Abamectin, ivermectin, moxidectin, doramectin, eprinomectin Parasite resistance has developed to each group of anthelmintic since they were introduced. Resistance to benzimidazole-based drenches is widespread throughout the world. Cases have been reported that involve resistance in all three major cattle parasite species: Ostertagia, Trichostrongylus and Cooperia.

Resistance to levamisole/morantel based drenches is well known but is less widespread than benzimidazole resistance.

In 1995, New Zealand researchers reported a strain of the worm parasite Cooperia that was resistant to both ivermectin (a member of the avermectin/milbemycin group) and to oxfendazole (a benzimidazole). In 1996, reports were published of an ivermectin resistant Cooperia strain that was cross-resistant to doramectin and moxidectin (also members of the avermectin/milbemycin group).

G:\00W771NZA Amended Spec 27March07.doc 3 To prevent and manage the problem of anthelmintic resistance farmers have relied on various strategies including: - minimizing anthelmintic use by treating only at strategically important times - alternating the type of anthelmintic used - using combinations of anthelmintics from different groups to reduce the potential of parasites to survive the treatment.

Orally administered combinations of benzimidazole and levamisole anthelmintics are well known, and have been used for many years.

However in recent years products based on actives selected solely from the avermectin/milbemycin groups have held the most significant share of the cattle anthelmintic market due to their high efficacy against the major production limiting parasite species, Ostertagia. The availability of easy to apply topical pour-on formulations has further 20 extended their market dominance.

By contrast, levamisole-based products have been used on a much more limited basis. Despite their having good efficacy against Cooperia, they have poor efficacy against Ostertagia, which is the parasite that anthelmintics of the avermectin/milbemycin group have 25 good efficacy against.

The table below shows that while each anthelmintic group has particular limitations against certain parasites, a combination of actives selected from the avermectin/milbemycin and levamisole groups would achieve two highly important goals: - high efficacy against the key cattle parasites combination potency to help prevent parasites surviving the treatment Anthelmintic Class Cooperia Efficacy Ostertagia Efficacy Levamisole Good Poor Avermectin/Milbemycin Poor Good Combination of both classes Good Good G:\00W771NZA Amended Spec 27March07.doc 4 Despite this rationale for an apparently easy to formulate product combining a levamisole active with an avermectin/milbemycin active, stable combinations have been difficult to formulate.

Ancare New Zealand Limited has previously attempted to produce a double active 10 formulation including levamisole and niclosamide. This was designed to target tapeworm and roundworm. This formulation however, was unsatisfactory as exposure to water made it too viscous to use.

Further it has been found that the differing pH requirements of levamisole and other 15 anthelmintics make it difficult to formulate a stable product.

NZ 336139 filed by Nufarm Limited represents a recent attempt to formulate a product containing a combination of an avermectin/milbemycin active and a levamisole active.

To achieve co-existance within the formulation, Nufarm relies on emulsion technology. The emulsion includes a formulation including the levamisole in aqueous acidic phase and including an anthelmintic such as an avermectin or milbemycin in the lipophilic phase. A third active can 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.

The complicated nature of the formulation in NZ 336139 is due in part to the different 30 formulation requirements of the actives. In particular, avermectins and milbemycins are substantially insoluble in water, whereas levamisole is water soluble. In addition, levamisole has previously been found to require a pH of less than about 4 for stability, while avermectins and milbemycins require a pH of about 6.6.

In addition to these stability issues, formulations which were intended for topical application had a tendency to cause skin irritation to the animal at the site of application. As will be G:\OOW771NZAAmended Spec 27March07.doc appreciated, to be acceptable for topical use a formulation must not cause excessive skin irritation.

Accordingly, there is a need for a stable anthelmintic formulation including avermectins or milbemycins together with levamisole, which is suitable for topical application.

OBJECT It is an object of the present invention to provide a stable anthelmintic formulation including an avermectin or milbemycin together with levamisole which is suitable for topical 15 application, or one that will at least provide the public with a useful choice.

STATEMENT OF INVENTION In one aspect the invention relates to a stable pour-on veterinary formulation suitable for 20 administration to animals containing at least two different anthelmintic actives, the first active being levamisole base and the second active being abamectin, wherein both of said actives are dissolved in a solvent system comprising n-methyl-2-pyrrolidone and diethylene glycol n-butyl ether.

Preferably the formulation contains about 20% w/v of levamisole base.

Preferably the formulation contains about 1% w/v of abamectin.

Preferably the formulation contains about 25% w/v of diethylene glycol n-butyl ether.

Preferably the formulation additionally includes at least one further medicament selected from the group comprising anthelmintics, dietary supplements, vitamins, minerals and other beneficial agents.

In a further related aspect the invention relates to a method of treating or preventing infection of animals with Cooperia or Ostertagia by administering to said animal an effective amount of a formulation of the present invention.

G:\O0W771NZA Amended Spec 27March07.doc DESCRIPTION The formulations of the present invention must be stable to be of commercial use. In this specification, a commercially acceptable anthelmintic formulation is one which is stable at room temperature for a period of at least 6 months. In conditions of accelerated testing, at 10 40°C, this requires the potency of the actives within the formulation to remain within specified and acceptable limits for 3 months.

Avermectins and milbemycins where used in this specification refer to a group of actives having anthelmintic activity. The avermectin group includes by way of example, avermectin, ivermectin, doramection and eprinomectin. The milbemycin group includes 15 moxidectin.

A large number of studies were undertaken over a 4 year period to develop a stable anthelmintic formulation combining levamisole and avermectin/milbemycin. In these studies abamectin was used as the representative avermectin/milbemycin active, whilst levamisole, in its base form, was used as the representative levamisole/morantel active.

Study 1 A number of potential formulations were prepared using a soya bean oil base and other common excipients used in the preparation of topical anthelmintics.

Formulation 1 Formulation 2 Materials %w/v Abamectin 1 Levamisole 20 Benzyl alcohol 5 Capmul PG-8 20 Isopropyl Palmitate 10 Tween 80 2 Soya bean oil q.v.

Materials %w/v Abamectin 1 Levamisole 20 Benzyl alcohol 5 Capmul PG-8 20 Isopropyl Myristate 10 Tween 80 2 Soya bean oil q.v.

Formulation 3 Formulation 4 Materials %w/w Abamectin 1 Materials %w/w Abamectin 1 G:\00W771NZA Amended Spec 27March07.doc 7 Benzyl alcohol Levamisole Capmul PG-8 Benzyl alcohol Isopropyl Palmitate Capmul PG-8 Tween 80 2 Isopropyl Myristate Soya bean oil q.v.

Soya bean oil q.v.

None of these test formulations were stable when tested under conditions of elevated temperature. All formulations exhibited significant degradation of the abamectin component. Animal studies also demonstrated an unexpected degree of skin irritancy when the formulation was topically applied, with hair loss occurring at the point of application. These results indicated that an oil-base to the product may be unsuitable both from an irritancy and stability perspective.

Study 2 A number of formulations were prepared using propylene glycol and glycol ethers, both common excipients used in veterinary drug formulation. These were then subjected to conditions of elevated temperature to determine their potential shelf stability. As a positive control for stability testing purposes, a commercially available avermectin/milbemycin product, Ivomec® Plus Injection, was used.

Formulations R20 R27 R28 R29 Ivomec® Levipor ® Ivomec® Plus injection Lev.base .0 g .0 g .0 g .0 g — .0 g — Abamectin l.Og l.Og l.Og l.Og -- -- — Ivermectin — — -- 0.5 g — 3.0 g Propylene Glycol 50 g 41 g 50 g 41 g Benzyl alcohol — -- g g BHT 0.2 g 0.2 g 0.2 g 0.2 g IPA 4g — 4g *DGMEE to 100ml 100ml 100ml 100ml * No more details *DGMEE: Diethylene glycol monoethyl ether (Transcutol ®) Stability results 0 day 5d lOd 15d 20d 25d /60°C /60°C /60°C /60°C /60°C G:\00W771NZA Amended Spec 27March07.doc 8 R20 Lev.base 100% 93.1 % 92.0 % 88.4 % 84.9 % Mm- 86.9 67.0 66.5 46.9 * solvent evaporated In all test formulations at elevated temperatures the abamectin component degraded significantly over the period of the study. The ivermectin component of the commercially available Ivomec® Plus formulation did not deteriorate to anywhere near the same extent as the abamectin component of the test formulations.

Whilst the levamisole component also deteriorated it did so at a much lower rate.

The study once again demonstrated the difficulty of combining the two actives and that the presence of levamisole was very problematic in preparing the combination formulation.

Study 3 A further range of test formulations were prepared in which benzyl alcohol was used to solubilise the abamectin component of the formulations.

Common stabilizing agents, BHT and BHA were also added to some of these test formulations.

G:\00W771NZA Amended Spec 27March07.doc Formulations Ingredients Concentration (%, w/v) 029/0 029/1 029/2/BH T 029/3/BH T 029/4/BH A 029/5/BH A Lev.base .0 .0 .0 .0 .0 .0 Abamectin 1.0 1.0 1.0 1.0 1.0 1.0 Propylene Glycol 41.0 41.0 41.0 41.0 41.0 41.0 Benzyl Alcohol — .0 .0 .0 .0 .0 Isopropyl myristate 4.0 4.0 4.0 4.0 4.0 4.0 BHT — -- 0.2 1.0 — — BHA — -- — 0.2 1.0 Diethylene glycol monoethyl ether to 100ml 100ml 100ml 100ml 100ml 100ml Stability results G:\00W771NZA Amended Spec 27March07.doc | Aba 100 % 47.8% 36.9% 33,m 100.9% 53.2% ND Ivomec® Iver 100 % 95.0% 98.0% 101.3% 100.3% 100.3% ND Levipor® Lev.bas e 100 % 102.0% 102.9% 100.9% 104.5% 94.9% ND In the stability study the presence of benzyl alcohol did not have any significant effect in minimizing the rate of degradation of the abamectin component of the test formulations. BHA and BHT also did not offer any advantage as stabilizing aids.

Study 4 A study was undertaken to determine whether the use of propylene glycol or glycol ethers would have any advantage in stabilizing the formulations.

Two test formulations were prepared as shown in the table below.

Formulations R 3 R 4 Levamisole base .0 g .0 g Abamectin l.Og l.Og Propylene glycol — 40 ml *DGBE to 100 ml 100 ml *DGBE: Diethylene glycol n-butyl ether (Butyl carbitol®) Stability results 0 day d/60°C d/60°C d/60°C d/60°C R3 Lev.base 100% 98.2% 99.0% 104.3% 100.5% R4 Lev.base -100% J [mi— |"l ()()>.. -- ii ■ -.v - a 95.5"., While levamisole base was relatively stable in both test formulations, the abamectin degraded in both test formulations with the rate of degradation much more significant in the test formulation that included propylene glycol. This suggested that propylene glycol was probably not beneficial in enhancing the stability of abamectin when used with DGBE.

G:\00W771NZA Amended Spec 27March07.doc 11 Study 5 A study was undertaken to attempt to improve the stability of test formulations that used DGBE as their base. Three test formulations were prepared as shown in the table below. BHT, was added as a stabilizing agent to two of the test formulations.

Formulations 3-1 3-2 3-3 Aba l.Og l.Og l.Og Leva.base .0 g .0 g .0 g BHT — 0.2 g 2.0 g *DGBE to 100 ml 100 ml 100 ml *DGBE: Diethylene glycol n-butyl ether Stability results 0 days 10days/60°C 20days/60°C 30days/60°C 3-1 Lev.base 100% 94.2% 96.7% 92.8% 3-2 3-3 Lev.base 100% 100% 100% 96.8% 7S.1H 98.0% J 54.1% 97.9% 91.1% 89.6% The study demonstrated that BHT had no significant effect on enhancing the stability of the 20 abamectin component of the test formulations.

Study 6 Further test formulations using benzoic acid and/or BHT were prepared as shown in the table 25 below, to evaluate the effects of benzoic acid and/or BHT on the stability of DGBE based formulations.

Formulations R1 R2 R3 R4 R5 R6 Lev.base .0 g .0 g .0 g .0 g .0 g .0 g Abamectin l.Og l.Og l.Og l.Og l.Og l.Og BHT — — 0.2 g 0.2 g 0.2 g Benzoic acid — 0.05 g 0.2 g — 0.05 g 0.2 g G:\OOW771NZA Amended Spec 27March07.doc 12 *DGBE to 100 ml 100 ml 100 ml 100 ml 100 ml 100 ml *DGBE: Diethylene glycol n-butyl ether Stability results 0 day lOd /60°C 20d /60°C 30d /60°C 1 Month /37°C 2 Months /37°C 3 Months /37°C R1 | Lev.base 100% 100.4% 98.9% 99.0% 98.7% 98.2% 98.6% These results demonstrate that neither benzoic acid nor BHT improved the abamectin component of the test formulations.

Study 7 A selection of new test formulations that included levamisole base, abamectin and other excipients with DGBE were prepared as shown in the table below.

Formulations R3 R4 R5 R6 Lev.base .0g .0g .0g .0g Lev.HCl — .0g — Aba l.Og l.Og l.Og l.Og P-CD 0.5g — — -- Benzoic acid — — .0g — Citric acid — — — 3.0g Propylene Glycol 40ml 40ml — — Glycerin Formal 30ml 30ml — — Capmul MCM — to 100ml — — G:\00W771NZA Amended Spec27March07.doc 13 DGBE to 100ml — to 100ml to 100ml R7 R8 R9 R10 Rll-1 Rll-2 R12 R13 R14 R15 Lev.base .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 g g g g g g g g g g Aba l.Og l.Og l.Og l.Og l.Og l.Og l.Og l.Og l.Og l.Og TEA — — — 1.0m 1 1.0m 1 1.0m 1 " — EDTA -- — -- -- 0.01 g — 0.01 g 0.01 g 0.01 g 0.01 g EDTA-2Na — — — 0.01 g — — BHT — — -- — 2.0g 2.0g 2.0g — 2.0g — BHA -- ~ — -- « ~ — 2-0g ~ 2-0g Benzoic acid — -- -- — — — .0g .0g DGMEE to 100 ml to 100 ml to 100 ml to 100 ml To 100 ml to 100 ml to 100 ml to 100 ml DGBE to 100 ml DPM to 100 ml TEA: Triethylamine; EDTA: Ethylenediaminetetraacetic acid; BHT: Butylated Hydroxy Tolueue; BHA: Butylated Hydroxyanisole; DGMEE: Diethylene glycol monoethyl ether; DGBE: Diethylene glycol n-butyl ether; DPM: Dipropylene glycol methyl ether Stability results G:\OOW771NZA Amended Spec 27March07.doc 14 These results show that none of the test formulations showed great promise in stabilizing the abamectin component of the formulations.

Study 8 A selection of new test formulations that included levamisole base, abamectin and other excipients with DGMEE were prepared as shown in the table below.

Formulations F1 F2 F3 F4 F5 F6 F7 F8 Lev.base .0g .0g .0g .0g .0g .0g .0g .0g Abamectin l.Og l.Og l.Og l.Og l.Og l.Og l.Og l.Og TEA 1.0ml 1.0ml — 1.0ml 1.0ml — — EDTA -- — — — -- — o.oig o.oig H20 — — -- lOg 10g 10g lOg BHT « « — ~ — -- 2.0g 2.0g BHA — -- — — — — — — Benzoic Acid .0g — .0g .0g — .0g — DGMEE to 100ml 100ml 100ml 100ml 100ml 100ml 100ml 100ml TEA: Triethylamine; EDTA: Ethylenediaminetetraacetic acid; BHT: Butylated Hydroxy Toluene; BHA: Butylated Hydroxyanisole; DGMEE: Diethylene glycol monoethyl ether G:\OOW771NZA Amended Spec 27March07.doc Stability results 0 day days/60°C days/60°C days/60°C F1 Lev.base 100% 99.6% 78.3% 63.8% Aba 100% 69.5% 38.5% .3% F2 Lev.base 100% 100.3% 100.3% 104.6% (?) Aba 100% 73.7% 50.2% 27.2% F3 Lev.base 100% 99.7% 99.9% 87.7% Aba 100% 52.3% 49.8% 26.9% F4 Lev.base 100% 34.4% 9.2% (?) 8.2% (?) Aba 100% 64.0% 52.8% 46.1% F5 Lev.base 100% 100.2% 97.2% 47.7% Aba 100% 32.7% No peak No peak F6 Lev.base 100% 47.9% 40.1% 34.5% Aba 100% 63.2% 55.5% 45.4% F7 Lev.base 100% 100.1% 99.0% 102.6% Aba 100% 72.6% 67.6% 53.9% F8 Lev.base 100% 100.3% 99.3% 98.1% Aba 100% 53.6% 26.8% (?) No peak These results show that once again none of the test formulations showed great promise in stabilizing the abamectin component of the formulations.

Study 9 Further alternative test formulations were prepared as shown in the table below. 15 Formulations R1 R2 R3 R4 R5 R6 Lev.base .0g .0g .0g .Og .0g .0 g Abamectin l.Og l.Og l.Og l.Og l.Og l.Og Benzoic Acid .0g .0g .0g .0g — -- Acetic acid — — — -- 2.0ml 4.0ml BHA — — 2.0g -- — — DGMEE to 100ml — — — -- — DGBE to — 100ml 100ml 100ml 100ml 100ml BHA: Butylated Hydroxyanisole; DGMEE: Diethylene glycol monoethyl ether; DGBE: Dithylene glycol n-butyl ether Stability results G:\00W771NZA Amended Spec 27March07.doc 16 0 day days/60°C days/60°C days/60°C* 85.5% 79.4% 38.2% 31.0% 73.9% 68.4% 73.5% 61.2% 47j% 38.8% 69.0% 50.6% 99.1% 100.4% ~~ 99.6% 99.3% R1 R2 100% R3 Lev.base Lev.base | 100% Lev.base 105.8% (?) R4 R5 R6 Lev.base 100% 100% torn !%_ 98.9% 98.5% 90.7% LevJbase | 100% Lev.base Aba 100% 100% 100.0°/, 99.8% 57.6% 52.4% *The temperature of the oven was changed to 55°C after storage for 20 days.

Again, none of these test formulations demonstrated great promise in stabilizing the abamectin component of the formulations.

Study 10 Further test formulations including acetic acid were prepared as shown in the table below. Formulations R1 R2 R3 R4 R5 Lev.base .0 g .0 g .0 g .0 g .0 g Abamectin 1.0 g l.Og l.Og l.Og l.Og Acetic acid — 2.0 ml 4.0 ml 6.0 ml .0 ml *DGBE to 100 ml 100 ml 100 ml 100 ml 100 ml *DGBE: Diethylene glycol n-butyl ether Stability results G:\00W771NZA Amended Spec 27March07.doc 17 These results show that formulations containing acetic acid did not improve the stability of the abamectin component. Also, the stability of levamisole base was adversely affected to a significant extent.

Study 11 A trial was carried out to determine whether the addition of varying levels of N-Methyl-2-pyrrolidone (Pharmasolv) to DGBE would enhance stability. All the test formulations were kept at 60°C and were analysed to assess the extent of degradation after 7,14 and 30 days.

Formulations G1 G2 G3 G4 G5 Lev.base .0% w.v. .0% w/v .0% w/v .0% w/v .0% w/v Abamectin 1.15% w/v 1.15% w/v 1.15% w/v 1.15% w/v 1.15% w/v DGBE - % w/v 40% w/v q/v. q.v.

N-Methyl-2-Pyrrolidone q.v. q.v q.v % Stability Results For m.

Initial 7 days at 60°C 14 days at 60°C days at 60°C Abame ctin Levamis ole Abamec tin Levamis ole Abamec tin Levamis ole Abamec tin Levamis ole G1 96.12 101.43 93.04 95.55 89.57 89.75 79.13 86.95 G2 100.24 103.22 95.65 99.50 95.65 96.35 79.13 93.60 G3 103.30 102.58 93.91 97.00 87.83 95.20 66.96 92.85 G4 109.05 101.70 101.74 99.95 93.91 99.35 66.57 93.80 G5 89.42 100.32 83.48 97.80 80.00 93.30 57.39 89.55 The stability results of the test formulations containing both the actives in N-methyl-2-pyrrolidone demonstrated that surprisingly a pyrrolidone based formulation was capable of significantly slowing the rate of degradation of both levamisole base and abamectin.

G:\00W771NZA Amended Spec 27March07.doc 18 To further confirm the findings of this study, new batches of test formulation were prepared as specified in the following table: Material Amount Lev.base .0% w/v Abamectin 1.15% w/v DGBE % w/v N-Methyl-2-Pyrrolidone q.v As shown in the table below, stability results over a twelve month period of storage at 25°C confirmed the findings of increased stability of an abamectin/levamisole formulation containing N-Methyl-2-Pyrrolidone and DGBE.

ACTIVE Initial 6 Months 12 Months Abamectin 104.00 102.55 99.95 Levamisole 99.75 99.00 98.55 Field Studies The test formulation as shown in the table above containing DGBE and N"methyl-2-pyrrolidone was used in a slaughter study to evaluate the effectiveness of the formulation in treating common cattle parasites, relative to formulations containing either solely a levamisole active or solely an avermectin or milbemycin active.

Table 1: Geometric mean total worm counts for calves treated with abamectin/levamisole combination pour-on formulation, Eprinex® pour-on formulation or Levipor® pour-on formulation in comparision with an untreated control group.

Treatment Control |Vba/Lev Eprinex® Levipor® «»o ■ (L l Ostertagia (adult) 11435.5s 4.4b 17.3b 5808.la Ostertagia (immature) 1274" 2.3b 0" 1317.4s T. axei (adult) 996.7a 0" 0" 110.9s T.axei (immature) 4.7a 0" 0a 1.9* Trichostrongylus spp (mature) 744.3a 6.7b 46.4a 5b G:\OOW771NZA Amended Spec 27March07.doc 19 Cooperia (adult) 15948.8" 1.9" 2155.8* .9b Cooperia (immature) 1598.7* 1.9b .7" 1.9d Oesophagostomum (mature) 2.5* 0a 0* 0* Trichuris (mature) .4" 0b 0" 0b * means within the same row with different superscripts are significantly different at p<0.05 Table 2: Treatment efficacies based on group geometric mean total worm counts.

Treatment Aba/Lev PO Eprinex® PO Levipor® 1 PO Ostertagia (adult) >99.9% 99.8% 49.2% Ostertagia (immature) 99.8% >99.9% 0% T. axei (adult) >99.9% >99.9% 80.1% T.axei (immature) >99.9% >99.9% >99.9% Trichostrongylus spp (mature) 99.1% 93.7% 99.3% Cooperia (adult) >99.9% 86.5% >99.9% Cooperia (immature) 99.8% 99.6% 99.9% Oesophagostomum (mature) >99.9% >99.9% >99.9% Trichuris (mature) >99.9% >99.9% >99.9% The results clearly demonstrated that whilst the levamisole-based formulation (Levipor®) performed poorly against Ostertagia and the eprinomectin-based formulation (Eprinex®) performed poorly against Cooperia, the abamectin/levamisole combination of the test formulation showed outstanding efficacy against all parasite species.

A large number of field studies on cattle of all ages also confirmed that in contrast with a number of the other test formulations, there is no skin irritation on treated animals when the formulation is topically applied.

PREFERRED EMBODIMENTS In the preferred embodiments, the formulations of the invention include an avermectin or milbemycin in combination with levamisole base and a pyrrolidone solvent. A glycol ether may additionally be included as a co-solvent.

G:\00W771NZA Amended Spec 27March07.doc Pyrrolidone solvents useable in this invention include, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1-pyrrolidone, N-ethylene-2-pyrrolidone, 3, 3-dimethyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 5-dimethyl-2-pyrrolidone, N-ethoxy-2-pyrrolidone, and combinations thereof.

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 The formulations of the present invention are prepared as follows: 1. Add levamisole base, avermectin/milbemycin and pyrrolidone to a mixing vessel. 2. Stir at room temperature until the actives have completely dissolved. 3. Add the glycol ether, if desired, and mix well. 4. Add the pyrrolidone to volume and continue mixing until a clear solution is obtained.

Topical Formulations 1. Examples of topically applied formulations of the invention include: Formulation 1.1 Ingredient % w/v Abamectin 1% Levamisole Base % N-methyl-2-pyrrolidone q.v.

Formulation 1.2 Ingredient % w/v Ivermectin 0.5% Levamisole Base % N-methyl-2-pyrrolidone q.v.

Formulation 1.3 Ingredient % w/v G:\00W771NZA Amended Spec 27March07.doc

Claims (6)

21 Ivermectin 0.5% Levamisole Base 10% DGMBE 25% N -methyl-2-pyrrolidone a.v. Formulation 1.4 Ingredient % w/v Eprinomectin 1.0% Levamisole Base 20% DGMBE 25% N-methyl-2-pyrrolidone q.v. 10 For topical administration to cattle, the formulations should generally be applied in a dose of about 1 ml per 10 kg to 1 ml per 20 kg. The present invention is advantageous as it provides stable veterinary formulations including an avermectin or milbemycin in combination with levamisole base. Further, the 15 formulations retain each active in solution. The formulations are monophasic and suitable to manufacture on a commercial scale. In addition, as both actives are in solution the formulations are physically stable, in that the solution does not separate out into separate phases, either aqueous and lipophilic phases or 20 liquid and solid phases. This enables the formulations to be used without requiring agitation or shaking before use, and greatly reduces the risk of differing concentrations of actives being present through the drum or other storage container. In addition, as the formulations exclude water the issue of incompatible pH requirements is 25 alleviated, enabling the two actives to stably co-exist in a single phase. G:\00W771NZA Amended Spec 27March07.doc 22 WE CLAIM:

1. A stable pour-on veterinary formulation suitable for administration to animals containing at least two different anthelmintic actives, the first active being levamisole base and the second active being abamectin, wherein both of said actives are dissolved in a solvent system comprising n-methyl-2-pyrrolidone and diethylene glycol n-butyl ether.

2. A stable pour-on veterinary formulation suitable for administration to animals as claimed in claim 1, wherein the formulation contains about 20% w/v of levamisole base.

3. A stable pour-on veterinaiy formulation suitable for administration to animals as claimed in claim 1 or 2, wherein the formulation contains about 1% w/v of abamectin.

4. A stable pour-on veterinary formulation suitable for administration to animals as claimed in any one of claims 1 to 3, wherein the formulation contains about 25% w/v of diethylene glycol n-butyl ether.

5. A stable pour-on veterinary formulation suitable for administration to animals as claimed in any one of claims 1 to 4, wherein the formulation additionally includes at least one further medicament selected from the group comprising anthelmintics, dietary supplements, vitamins, minerals and other beneficial agents.

6. A method of treating or preventing infection of animals with Cooperia or Ostertagia by administering to said animal an effective amount of a formulation as claimed in any one of claims 1 to 5. intellectual property office of n.2. 21 MAR 2006 -RECEIVFn 00W771NZA Amended Claims for Divisional.doc