WO2001020994A1

WO2001020994A1 - Sheep pour-on

Info

Publication number: WO2001020994A1
Application number: PCT/NZ2000/000185
Authority: WO
Inventors: Colin Manson Harvey; Morgan John Mcarthur; Ivor Blair Loveridge
Original assignee: Ashmont Holdings Limited
Priority date: 1999-09-22
Filing date: 2000-09-22
Publication date: 2001-03-29
Also published as: ZA200202557B; AU7463000A; EP1215964A1; EP1215964A4; AU733095B3

Abstract

A stable pour-on formulation for treatment of both internal and external parasites of sheep. The active is an avermectin or milbemycin. The formulation is designed to rapidly penetrate the fleece to provide a measurable therapeutic blood level of the active. It includes benzyl alcohol as a solvent, butyl dioxitol as a penetrating agent, and a spreading agent such as a crodamol GTCC and dowanol DPM.

Description

SHEEP POUR-ON

Field of the Invention

This invention relates to the field of veterinary compositions, and more panicularly anthelmintic compositions suitable for topical application to ovine.

Background

Effective pour on formulations for ovine are difficult to formulate due to the barrier provided by the dense mat of wool. Wool grease within the wool on the skin makes it extremely difficult to obtain safe and effective therapeutic blood plasma levels of an active from application of a pour- on.

Object

It is an object of the present invention to provide an improved ovine pour on formulation or one, which at least provides the public with a useful choice.

Statement of Invention

The present invention relates to a pour-on formulation suitable for administration to sheep for the control internal and external parasites, which includes an active selected from the group of avermectins and milbemvcins. at least one solvent, and one or more penetratins agents. Preferably the pour on formulation as claimed is capable of registration (or is registered) as a licensed Animal Remedy (by this we mean that it meets the regulatory requirements of a veterinary product (typically called an Animal Remedy) in the country in which it is to be sold/used. For example in New Zealand this has hitherto involved registration as a licensed 5 Animal Remedy under the Animal Remedies Act. or in Australia it requires registration with the National Registration Authority. This provides a practical standard for, inter alia: stability, safety and efficacy of a particular product. It will be appreciated this is panicularly important in the case of animals farmed for food production (examples include sheep and lambs) where residue levels and toxicity of the formulation may have relevance to the usefulness or otherwise 10 of the animal for food purposes.

More preferably the active is selected from the group comprising abamectin, ivermectin, doramectin and moxidectin.

15 Preferably the active is present in the range 1 -4%w/v.

Preferably the penetrating agent is selected from the group including polyethylene glycol, glycol ethers and aromatic solvents.

20 More preferably the penetrating agent is dipropylene glycolmethyl ether, xylene. toluene or butyl dioxitol (also known as diethylene glycol butyl ether (DGBE).

A panicularly preferred glycol ether is butyl dioxitol.

25 Preferably the composition will include a water soluble organic solvent for dissolving the anthelmintic.

Preferably the solvent is selected from the group comprising benzyl alcohol, ethyl lactate and glvcerol formal.

Preferably the pour-on formulation also includes a spreading agent. Preferably the solvent is present in the range of 1 -50% w/v.

Preferably the composition is able to safely deliver a dose of 2-4 m/kg of active to control internal and external parasites.

Preferably the composition provides effective blood levels of active in the range of 2-5 ng/ml.

More preferably the endo parasites controlled are parasitic gastro-intestinal nematodes of ovine and the control achieved results in at least a 95% reduction in faecal egg counts.

Preferably the formulation is effective where the ecto parasites to be controlled are lice and psoroptic mange.

In a particularly preferred aspect the invention provides a stable pour-on formulation for treatment of both internal and external parasites of sheep containing an active selected from the class of avermectins and milbemycins. wherein the formulation is designed to rapidly penetrate the fleece to provide a measurable therapeutic blood level of the active, and wherein the formulation contains: (i) a solvent selected from the group comprising benzyl alcohol, ethyl lactate and glycerol formal, and (ii) a penetrating agent selected from the group comprising propylene glycol. glycol ethers and aromatic solvents, and (iii) a spreading agent.

Preferably the active is one or more of abamectin. ivermectin, doramectin or moxidectin.

More preferably the penetrating agent is a glycol ether and the formulation is capable of achieving effective blood levels in sheep of active in the range of 2-5ng/ml of blood, when the pour on is administered at a dose rate of 2-4mg of active per Kg of body weight. Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Preferred Embodiments

The following examples are given by way of example only and should not be taken as being in any way limiting the spirit and scope of the invention.

It has been discovered it is possible to formulate stable safe and effective formulations which combine avermectins or milbemvcins together with agents which are able to rapidly penetrate the fleece and wool grease to obtain therapeutic blood levels of actives as well as spreading quickly over the animal thus a high level of control of both ecto and endo parasites in ovine is achieved.

An example of the formulation of the present invention is given below.

Formulation Example 1 (Formulation 1)

Abamectin 1 %

Benzvl Alcohol 5% Crodamol GTCC 30%

Butyl Dioxitol to volume

The abamectin is dissolved In a premix of benzyl alcohol at 50°C. Crodamol GTCC is added and the formulation Is made up to volume with Butyl Dioxitol.

Formulation Example 2 (Formulation 2)

Abarriectin 1 %

Dowanol PM 30%

Senzyl Alcohol 5%

Polyethylene Glycol to volume

THals

A ."tiUrtlber of trials were conducted to confirtn the stability, safety arid feffϊcacy df the formulations, the subject of this patent.

Stability Trials

To test the stability of the formulation two batches of Formulation 1 were made according to the directions and tested for seven days at 0°C and for three months at 38°C.

The formulation was found to be stable at both temperatures. Both batches were also subject to a BP microbiological challenge and were shown to be robust for general use.

Safety Trials

The use of such high levels of active was considered a potential hazard as residues can effect the market quality of sheep treated. A further study was undertaken to examine the therapeutic blood levels achieved and the impact on wool and tissue residues. Three to four month old Border Leicester x Dorset lambs were selected for the study to determine the concentration of avermectin B in plasma, edible tissues and wool after treatment with Abamectin Pour-on formulation of Example 1. The sheep were grazed at Massey University^'s Jennersmead Farm, Palmerston North. New Zealand for the duration of the study.

The sheep were restrictively randomly allocated on the basis of sex and weight to groups as follows: ten animals to Group 1. fifteen animals to Group 2. Groups 1 and 2 were treated on Day 0 with Abamectin Pour-on formulation of Example 1 at a dose rate of 4mg avermectin Bi_a/kg bodyweight. All lambs were 3 '/_ weeks off shears at the time of treatment.

Wool specimens were collected from animals in Group 1 immediately prior to treatment and on Days 1. 5. 1 1. 20. 40. 81 and 120 after treatment. The wool specimens were collected in 13-15 cm wide bands clipped around the circumference of the body between the withers and rump.

The actual site of sampling for each animal at each interval was determined using random numbers prior to the commencement of the study. Blood specimens were collected from the jugular veins of animals in Groups 1 and 2 at pre-treatment, 6 and 12 hours and Days 1, 2. 3, 5, 7. 1 1. 15. 20, 29 and 40 after treatment. Animals were sacrificed in sub groups of five at Days

21. 28 and 35 (Group 2) after treatment for the collection of muscle, fat. liver and kidney specimens.

Wool specimens were analysed by WRONZ Developments. Christchurch. New Zealand. Plasma was harvested from the blood specimens and analysed, along with the tissue specimens by Amdel NZ Ltd. Auckland. New Zealand. All specimens were analysed for avermectin B_{! a} using HPLC with fluorescence detection.

The results obtained show the maximum mean plasma avermectin B_{i a} concentration for animals treated with the pour-on formulation was reached 24 hours after treatment. This ranged from 12 to 72 hours in individual animals. The mean plasma concentration was just above the limit of qtiantitation (LOQ) for the analytical method by Day 1 1 after treatment. Avermectin Bι_a levels in all tissue specimens were below the LOQ for the analytical method (3 ng/g).

Within six hours of treatment with Formulation 1 plasma avermectin Bι_d concentrations were elevated within 6 hours of treatment. The group mean concentrations were at their highest 24 hours after treatment (Figure 1 and Table 1 ). By Day 1 1 after treatment, the group mean concentration ( 1.1 ng/mL) was just above the limit of quantitation of 1 ng/mL.

Table 1 Mean plasma avermectin B _a concentrations (ng/mL) of sheep treated with Formulation 1 on Day 0

Note 1 ng/mL = limit of quantitation for analytical method

The pharmacokinetic parameters, including Cmax. Tmax, T_{) 2} and AUC. are shown in Table 2. The Cmax in most animals was reached at 24 hours, but this ranged from 12 to 72 hours in individual animals. The Cmax was also variable, from 1 ng/mL in animal 510, to 26.3 ng/mL, in animal 519.

All the tissue avermectin B_{i a} concentrations were below the LOQ of 3 ng/g by 21 days after treatment for the animals treated by Pour-on (Table 3).

Table 3. Group mean avermectin B_1a concentrations (ng/g) in the tissues of sheep treated on Day 0.

Tissue

Group n^a Test substance Study Day Muscle Kidney Liver Fat

2 5 Formulation 1 21 <3 ng/g <3 ng/g <3 ng/g <3 ng/g

5 28 <3 ng/g <3 ng/g <3 ng/g <3 ng/g

5 35 <3 ng/g <3 ng/g <3 ng/g <3 ng/g

n^a = number of animals

Wool levels of Abamectin Bi_b are shown in Table 4. Table 2. Pharmacokinetic parameters of plasma avermectin B_1a concentrations (ng/mL) of sheep treated with Formulation 1 on Day 0

Animal ID Tmax (hours) Cmax (ng/mL) T1/2 (hours) AUCIast (ng/mL x hrs)

485 12 189 753 20949

497 24 26 1208 3360

498 24 35 728 4398

500 24 112 652 10374

501 24 59 701 8250

508 24 71 726 9777

509 24 57 900 7074

_*

510 0 10 2640

518 24 52 549 5556

519 24 263 493 17979

521 24 46 934 4776

522 24 89 1028 11490

525 24 43 737 5682

526 24 157 578 11607

527 24 108 493 6723

529 24 44 1069 3828

531 24 35 1039 3663

536 24 86 477 9045

538 24 54 576 6843

539 24 78 546 7788

540 72 100 1337 15531

541 48 72 1253 12552

542 24 71 556 7284

543 24 52 571 5682

544 120 39 948 6042

mean 293 779 7855 83557 std dev 225 557 2610 46163 std error 75 186 870 15388

^* = could not be calculated Table 4. Group mean wool avermectin B_1a concentrations (mg/kg) of sheep treated on Day 0

Study Day

-1 1 5 11 20 40 81 120

7 real meat hoop hoop B c D hoop A B c D hoop A B c D hoop A B c D hoop hoop hoop

A l

Pour on XV 1₄ 1 44 135 01 NP NP NP NP 16 73 21 24 22 26 16 66 2 55 SP 5 95 7 53 8 47 3 38 SP 2 42 2 30 2 03 1 44 SP 1 44 1 44 lowei limil 95°/ Cl 1 44 72 68 8 03 5 68 6 25 3 08 0 48 0 18 3 47 2 51 0 75 0 16 1 47 0 66 1 44 1 44 _! upper limit 95 %CI 1 44 197 34 25 43 36 78 38 25 31 22 4 56 11 68 11 58 14 39 5 95 4 60 3 09 3 33 1 44 1 44

Control 1 44 1 44 NP NP NP NP 1 44 NP NP NP NP 1 44 NP NP NP NP 1 44 NP NP NP NP 1 44 1 44 1 44 > B

NP = Samples not partitioned SP5= Samples partitioned _!

Comparative Efficacy Trials

Further trials were conducted to determine the comparative efficacy of the compositions of this invention.

In particular the effect of treatment with the Formulation 1 (above) was compared with an untreated control treatment, a 2.5% triflumuron treatment and treatment with a 25% triflubenzuron composition. Three trials were conducted. The treatments were kept constant throughout the three trials.

1. The Control Group

The control group of animals had comparative parasite burdens to the other test animals but remained untreated throughout the trials.

2. Triflumuron Treatment (EXIT)

The triflumuron treatment consisted of the application of a 2.5% composition of triflumuron. The triflumuron was applied as a spray on. A dose of 20ml per animal was applied.

3. Diflubenzuron Treatment (Fleecemaster)

2.5% diflubenzuron concentrate was diluted to 0.0625% and jetted onto target animals at a rate of 1 L per animal.

4. FE1 (Example 1 formulation)

A 1% abamectin oil based composition was applied as a pour-on at a dose rate of 4mL/10kg. The pour-on was applied at skin level along the midline of the back.

Trial 1

Trial 1 is the only one of the trials, which did not include the diflubenzuron treatment. As can be seen from Figure 2 there were no significant differences between the numbers of lice on sheep between the various treatment groups before treatment. However after lice treatments were administered all animals treated showed decreases in lice numbers. This was confirmed at the 1 month lice count. The most effective of the treatments at the 1 month stage was Formulation 1 which showed a 99% decrease in lice numbers. The triflumuron treatment similarly showed a decrease although this did not reach 98% until the lice count at the end of month 2. From month 3 to 5 the lice kill was 100%) for both treatments.

Trial 2

Trial 2 involved 40 female hoggets. Comparison was made between treatments as described above (treatments 2-4). Specifically the 40 animals were randomly allocated to 5 groups, 1 untreated control group, a second treated with EXIT™ (triflumuron spray-on), a third with FleeceMaster™ (diflubenzuron jetting fluid) and a fourth group treated with the formulation. The final group was an untreated control group used to provide louse challenge to the treated group. The untreated control groups were run separately from the treated groups.

Lice counts were conducted at the conclusion of each month for the 6 months following treatment. The lice challenge took place as soon as practical and at least within a few days. The results are displayed in Figure 3.

The results clearly show that the formulations of the present invention provide effective treatment against lice infestations.

At 3-5 months lice were not detectable on animals treated by any one of the three methods treatments.

At 6 months lice counts were found to be 0.1 lice for animal per all treatment.

Trial 3

This trial was similar to trial 2 in that all three treatments were compared. However only one control (untreated) group was used. All three treated groups were run together. The untreated control group was run separately.

This trial ran for 7 months from the date of treatment, with lice counts performed on a monthly basis. All treatments were found to be 100% effective at eliminating lice infection at 3-7 months post treatment. The composition of the present invention can be seen to provide effective fast treatment. Figure 4 clearly shows that the lice count for this treatment was decreased to a non detectable level within the first month and remained consistently low for the course of the trial.

Advantages

The formulations of the present invention advantageously provides stable safe formulations of active that rapidly penetrate the fleece to obtain therapeutic blood levels as well as spreading quickly within the animal achieving a high level of control of ecto as well as endoparasites in ovine.

The formulations of the present invention are stable over time to allow their practical use on sheep.

The formulations are safe for both sheep and man. There is no undue irritation and residue levels that result from the use of the present invention reach acceptable levels in a practical time for farmers. Advantageously the formulations do not damage the valuable wool present on the animal or attract dust or other foreign matter to the fleece.

The formulations give measurable therapeutic blood levels of the active and give a high level of control in excess of 95% of the population of external parasites such as lice and internal nematodes of all major species.

Finally, it will be appreciated that various alterations and modifications can be made to the forgoing without departing from the scope of the invention as set forth.

Variations

The formulations may be varied by using a variety of different spreading agents or thickeners, in addition to or in place of those described herein.

Suitable spreading agents for inclusion in the compositions of the present invention include crodamol GTCC and dowanol DPM. SuittlBle thickeners for inclusion in the compositions of the present invehtidii ihtlttde oat tiled flour, methancel and xanthan gum.

Thbse skilled In the an will appreciate that other exipients may be included in the composition of the present invention these may include by way of example dyes.

In some cases a solvent may function as both a solvent and penetrating agent, although in all of our examples we have used different ingredients for these two functions.

Additional penetrating agents may be used in conjunction with the general class of penetrating agents mentioned in the description and in the claims.

Alsd additional solvents may be used in conjunction with the general class of Solvents rrie tioned in the description and in the claims.

Flriklly various othet alterations or πioi iflcatiohs tnay be iade to this f tfe^diϋg withbUt idej._l_-.ihg from the scope of the Invention as set forth In the appendarit clalftis:

Claims

CLAIMS:

1 . A stable pour-on formulation suitable for administration to sheep to control internal and external parasites, which includes an active selected from the group of avermectins and milbemvcins. a solvent, and one or more penetrating agents.

2. A stable pour-on formulation as claimed in claim 1. when registered as a licensed Animal Remedy.

3. A stable pour-on formulation as claimed in any previous claim, wherein the active is selected from the group comprising abamectin. ivermectin. doramectin and moxidectin.

4. A stable pour-on formulation as claimed in any previous claim wherein the active is present in the range l -4%w/v.

5. A stable pour-on formulation as claimed in any previous claim, wherein the penetrating agent is selected from the group including propylene glycol. glycol ethers and aromatic solvents.

6. A stable pour-on formulation as claimed in any previous claim, wherein the penetrating agent is butyl dioxitol.

7. A stable pour-on formulation as claimed in any previous claim, wherein the solvent is selected from the group comprising benzyl alcohol, ethyl lactate and glycerol formal.

A stable pour-on formulation as claimed in any previous claim, which also includes a spreading agent.

A stable pour-on formulation as claimed in any previous claim, wherein the solvent is present in the range of 1 -50% w/v.

A method of providing effective control of internal and external parasites of sheep by application of a pour on formulation as claimed in any previous claim to the sheep at a rate of 2-4mg of active per Kg of body weight.