GB2148119A

GB2148119A - Parasiticidal formulations

Info

Publication number: GB2148119A
Application number: GB08423263A
Authority: GB
Inventors: Andrew R Galbraith; John M Ballany
Original assignee: Janssen Pharmaceutica NV
Current assignee: Janssen Pharmaceutica NV
Priority date: 1983-10-17
Filing date: 1984-09-14
Publication date: 1985-05-30
Also published as: GB8423263D0; IE56159B1; IE842650L; ZA848072B; AU565495B2; NZ209781A; GB8327761D0; GB2148119B; AU3428184A

Abstract

Stable pour-on formulations, combining tetramisole or levamisole with a synthetic pyrethroid, which contain one or more optionally substituted aliphatic carboxylic acids having a pKa-value in the range of 0.6 to 6. The pyrethroids are e.g. deltamethrin, cyhalothrin, cyfluthrin, flumethrin, cypothrin and fenvalerate.

Description

SPECIFICATION Parasiticidal formulations This invention relates to parasiticidal formulations which are useful in eradicating and/or controlling both endo- and ectoparasites attacking warm-blooded non-human animals.

Animals like sheep and cattle are often simultaneously infected by both endoparasites, such as gut and lungworms, and ectoparasites such as, for example, lice, keds, mites, ticks and fleas.

Most parasiticidal compounds have a rather selective activity: some compounds have predominantly ectoparasiticidal activity while other compounds have predominantly endoparasiticidal activity. In order to control both types of parasites, separate applications of an endoparasiticide and of an ectoparasiticide will generally be required.

One effective and preferred endoparasiticidal, and more specifically anthelmintic, compound is 2,3,5,6 -tetrahydro - 6 - phenylimidazo[2,1 - b]thiazole, the racemic form of which is generically designated as tetramisole, while the laevorotatory form; which bears most of the anthelmintic activity, is generically indicated as levamisole. Tetramisole and levamisole are described e.g. in British Patent Nos.

1,043,489, respectively 1,152,544.

An important group of insecticides, which are increasingly used to eradicate ectoparasites on animals, are the synthetic pyrethroids, which combine great ectoparasiticidal activity with a relatively high degree of safety towards animals and humans. Potent insecticides within the group of synthetic pyrethroids are, for example, cypermethrin, deltamethrin, cyhalothrin, flumethrin, cyfluthrin, tralomethrin, tralocythrin, fenvalerate, permethrin and phenothrin.

In view of the desirability to control both endo- and ecto-parasites simultaneously with one treatment, it would obviously be a desirable objective to combinetetramisole or levamisole with an appropriate pyrethroid in one single formulation for application to the infected animals. Preferably such a formulation would be a pour-on or spot-on formulation, wherein the active compound is dissolved or suspended in a suitable solvent or carrier and poured directly on to an infested animal, e.g. along the backline, or discrete spots are locally applied. Various anthelmintic pour-on compositions which contain levamisole as an active ingredient are now widely used in practice. In U.K.Patent Application No. 2,110,092 A there are described certain pour-on formulations, which comprise a mixture of cyhalothrin with levamisole or tetramisole free base in a carrier comprising particular combinations of an alcohol solvent with an ester co-solvent.

In a preferred embodiment, the compositions are taught to contain one or more carboxylic acids selected from the group consisting of C to C8 alkanoic acids. According to the reference, the molar ratio of alkanoic acid to levamisole free base should not exceed 1.1 and most preferably the alkanoic acid and levamisole free base are in substantially equimolar proportions.

It has however been found that-synthetic pyrethroids tend not to be stable when incorporated in a pour-on formulation which further comprises tetra- or levamisole, such as those described in U.K. Patent Application No. 2.110.092 A. As a matter of fact, it has been observed that, when such formulations are stored for some time, a considerable part of the synthetic pyrethroid is destroyed, giving rise to ineffective formulations. It is therefore an object of th is invention to provide pour-on formulations which comprise levamisole or tetramisole in combination with a pyrethroid and which are stable for a sufficiently long period of time, preferably at least 6 months, by preventing or at least retarding any decomposition of the individual active ingredients.

A further object is to provide a pour-on or spot-on endo- and ectoparasiticidal formulation of levamisole or tetramisole and a synthetic pyrethroid in a suitable solvent and which retains useful or unimpaired efficacy against parasites after storage of the formulation for a prolonged period e.g. greater than one year.

As used herein, the term "parasites" is meant to include endoparasites, e.g. gut and lungworms, as well as ectoparasites, e.g. lice, keds, mites, ticks, fleas, blowfly. The term "controlling parasites" is meantto include the killing and/or the interference with the development and/or reproduction of said parasites.

The term "unimpaired efficacy" means that the formulation have an efficacy which is unimpared in comparision with the efficacy of two compositions comprising the same amount of levamisole and a synthetic pyrethroid separately.

The term "useful efficacy" means that the formulations have an efficacy greater than that of a mixture which has undergone decomposition but less than unimpaired efficacy.

According to the invention, it has been found that pour-on formulations which combine tetramisole or levamisole with a synthetic pyrethroid can be made stable by adding thereto one or more optionally substituted aliphatic carboxylic acids having a pKa value in the range of 0.6 to 6, said acid or acids being present in a proportion of at least 1.5 and preferably at least 2.5 acid equivalents per mole of tetramisole or levamisole.

In principle there is no upper limit to the acid content of the formulation, but, for reasons of acceptability and lack of irritation, the acid component should not represent more than about 40% (w/v) and preferably not more than 35% (w/v) of the formulation.

Consequently, there are provided by the subject invention parasiticidal compositions which comprise in admixture; i) an anti-ectoparasitic amount of a pyrethroid having the formula

wherein: Y is hydrogen or cyano; Rishydrogen or halo; Q is CH or N; and L is a radical of the formula

wherein: R1 is halo or lower alkyl, and R2 is halo, lower alkyl, halophenyl ortrifluoromethyl;

wherein each of R3, R4, R5 and R6 is halo,

wherein: n isO or 1, R7 is halo, trifluoromethyl or difluoromethoxy, and R8 is hydrogen or halo; provided that when said R is hydrogen and said R' and R2 are both chloro, then said Q is N; ii) an anthelmintic amount of levamisole or tetramisole or a mixture thereof; iii) at least one optionally substituted carboxylic acid having a pKa value in the range of 0.6 to 6, said acid or acids being present in a proportion of at least 1.5 acid equivalents per mole of levamisole and/or tetramisole; and iv) a solvent.

Similar compositions containing a combination of tetramisole and/or levamisole with cypermethrin as an insecticidal active ingredient are described and claimed in ourcopending PCT-Application No.

GB-83/00166, filed on June 1983. The compositions described and claimed therein are excluded from the scope of the subject invention.

Specific pyrethroids of formula (I) which can advantageously be used in compositions according to the subject invention are listed in the following Table I.

TABLE I: Components of formula I

L Q R Y Generic designation ,C1 -CH- CH-CH=C N H CN DOWCO-417 H3CXCH3 N ,eBr -CH-CH-CH=C CH H CN Deltamethrin g3CXCH3 Br 3 3 C1 -CH-CH-CH=C CH H CN Cyhalothrin H3CXcH3 CF3 Cl -CHCH-CH=Co CH F CN Cyfluthrin I/ Cl H3C8EI3 CH3 CH H CN Cyphenothrin -CA -PU-CII=C CH H 3 Cl -CH--CH-CH=C CH F CN Flumethrin H3CH3 Cl / Br -CH-CH-CH-C CH H CN Tralomethrin I I H3C/CH3 Br Br Br -CH4ICH-C/ CH H CN Tralocythrin INBr 3 C1l Cl CH -(31-- 3 CH H CN Fenpropathin -CH- C CH C"3 CHC'm CH H CN Cypothrin 3 3 TABLE I (contd.)

L O R Y Generic designation -CH / \Cl CH H CN Fenvalerate CEX CR CR3 CR3 -CR -CRF2 CH H CN AC-222705 I CR CH3 CH3 H- CF3 CH H CN Fluvalerate C CR 3 C 3 Cl -CR- CR-CR-C CH H H Permethrin R3CXCR3 CR -CR - CR-CR=C 3 CH H H Phenothrin CR3 H31:XCH CH3 .

It is understood that formula I as used herein covers all isomeric forms and mixtures thereof, including geometric isomers (cis and trans) and optical isomers.

Particularly potent insecticides within the group of synthetic pyrethroids are those wherein the ester group is derived from an a-cyano alcohol, i.e. the synthetic pyrethroids of formula (I) wherein Y is cyano.

Pour-on compositions containing said pyrethroids, hereinafter referred to as a-cyanopyrethroids, are particularly preferred within the present invention.

The preferred acids are optionally substituted aliphatic carboxylic acids having a pKa value between 0.6 and 6. Suitable acids are citric acid, acetic acid, malonic acid, propionic acid, lactic acid, malic acid and the like. Either one single acid or a combination of acids may be used. The acid(s) should be selected to minimize any irritation to the animal and maximized stability. Preferred acids are acetic, propionic and citric acid.

The solvents selected for the formulations of the invention may be known insecticidal solvents.

Selection is based on the following criteria: a) ability to dissolve the active ingredients, and the stabilizing acid(s), b) ability to facilitate the spread of the pyrethroid across the skin surface of the target species, c) ability to facilitate penetration of the levamisole through the skin of the target species, d) avoidance of significant adverse skin reactions on the target species, e) avoidance of troublesome properties such as toxicity, inflammability, unacceptable odour, high freezing point.

The solvent choice for c) and d) will depend on the target species. Solvent system with no drawbacks on cattle may not be acceptable for treatment of sheep, and vice-versa. Also, it is unlikely that one single solvent will meet all the above criteria.

Among suitable solvents for selection are ether-alcohols such as butyl dioxitol, monoterpenes containing hydrocarbon and ether functions such as eucalyptus oil and terpinolene, and polar oxygenated solvents such as dimethyl sulfoxide and dimethylformamide.

In order to stabilize the formulation it may be advantageous to include in small quantity an appropriate anti-oxidant, e.g. an alkylated phenol such as BHT(butylated hydroxy toluene) or BHA (butylated hydroxy anisole).

As an example, the ingredients can be dissolved in one or more ether-alcohols of the formula

wherein m is 1,2 or 3, R is C1-C6 alkyl and R1 is hydrogen or methyl.

One suitable ether-alcohol is 2-(2-butoxyethoxy)ethanol wherein m is 2 and R=ethyl. The solvent may comprise a major part of this ether-alcohol which exhibits excellent spreading and absorption characteristics.

Although the compositions according to the invention may contain either tetramisole or levamisole or a mixture of both as an active ingredient, the use of levamisole is definitely preferred.

The concentration of the active ingredients in the formulation will depend on their parasiticidal potency, the nature of the animal to be treated, the parasites to be controlled and the desired volume to be poured on to the animal. For levamisole a normal dose will usually be in the range of 5--15 mg/kg of liveweight. Suitable pour-on formulations according to the subject invention will appropriately contain from about 4 to about 20% of levamisole.

The concentration of the pyrethroid of formula I in the formulation will largely depend on its anti-parasitic potency but will in general be from about 0.5 to about 10%.

According to a second aspect, there is provided by the subject invention a method of controlling parasites in non-human animals by applying to the animal a pour-on or spot-on formulation according to the first aspect.

The following examples are intended to illustrate and not to limit the scope of the present invention.

Experimental part EXAMPLE I A pour-on formulation is prepared by mixing the following ingredients: levamisole lOg deltamethrin 2 g citric acid 20 g acetic acid lOg 2-(2-butoxyethoxy)ethanol balance to 100 ml.

The formulation is stable for at least 6 months.

EXAMPLE II A pour-on formulation is prepared by mixing the following ingredients: levamisole lOg cyhalothrin 2g citric acid 20 g acetic acid lOg dimethyl sulfoxide balance to 100 mi.

The formulation is stable for at least 6 months EXAMPLE Ill A pour-on formulation is prepared by mixing the following ingredients: levamisole 8 g deltamethrin 1 g malonic acid 20 g BHT 1g dimethyl suifoxide balance to 100 ml.

The formulation is stable for at least 6 months EXAMPLE IV A pour-on formulation is prepared by mixing the following ingredients: levamisole lOg permethrin 2g citric acid 20 g acetic acid lOg dimethyl sulfoxide balance to 100 ml.

The formulation is stable for at least 6 months EXAMPLE V Pour-on formulae are prepared by dissolving together: I) Levamisolebase 20 g deltamethrin 2g butyl dioxitol balance to 100 ml.

II) levamizole base 20 g deltamethrin 2 g malonic acid 20 g butyl dioxitol balance to 100 ml.

These formulations are clear straw-coloured liquids. Storage at ambient temperature gave the following results: II Original analysis levamisole 20.5% 19.7% deltamethrin 2.0% 2.4% visual clear straw clear straw After 1 month levamisole 20.1% 19.4% deltamethrin 0.4% 2.6% visual dark amber clear straw

Claims

1. A pour-on composition for combating parasitic infestations in warm-blooded, non-human animals, which comprises in admixture: i) an anti-ectoparasitic amount of pyrethroid having the formula

wherein: Y is hydrogen or cyano; R is hydrogen or halo; Q is CH or N; and Lisa radical of the formula

wherein: R1 is halo or lower alkyl, and R2 is halo, lower alkyl, halophenyl or trifluoromethyl;

wherein each of R3, R4, R5 and R6 is halo;

wherein n isO or 1, R7 is halo, trifluoromethyl or difluoromethoxy, and R8 is hydrogen or halo; provided that when said R is hydrogen and said R1 and R2 are both chloro, then said Q is N; ii) an anthelmintic amount of levamisole or tetramisole or a mixture thereof; iii) at least one optionally substituted carboxylic acid having a pKa value in the range of 0.6 to 6, said acid or acids being present in a proportion of at least 1.5 acid equivalents per mole of levamisole and/or tetramisole; and iv) a solvent.

2. A pour-on composition according to claim 1 wherein the synthetic pyrethroid is a a-cyanopyrethroid.

3. A pour-on composition according to any of claims 1 to 2 containing levamisole as an anthelmintic active ingredient.

4. A pour-on composition according to any of claims 1 to 3 wherein said pyrethroid is deltamethrin.

5. A pour-on composition according to any of claims 1 to 3 wherein said pyrethroid is cyhalothrin.

6. A pour-on composition according to any of claims 1 to 3 wherein said pyrethroid is cyfluthrin.

7. A pour-on composition according to any of claims 1 to 3 wherein said pyrethroid is flumethrin.

8. A pour-on composition according to any of claims 1 to 3 wherein said pyrethroid is cypothrin.

9. A pour-on composition according to any of claims 1 to 3 wherein said pyrethroid is fenvalerate.

10. A pour-on composition according to any of claims 1 to 9 which comprises from 4 to 20% (w/v) of levamisole.

11. A pour-on composition according to any of claims 1 to 10 which comprises from 0.5 to 10% (w/v) of the pyrethroid.

12. A pour-on composition according to any of claims 1 to 11 wherein said carboxylic acid is present in a proportion of at least 2.5 acid equivalents per mole of levamisole and/or tetramisole.

13. A pour-on composition according to any of claims 1 to 12 wherein said carboxylic acid is acetic acid.

14. A pour-on composition according to any of claims 1 to 12 wherein said carboxylic acid is-citric acid.

15. A pour-on composition according to any of claims 1 to 12 wherein said carboxylic acid is acetic acid and citric acid.

16. A pour-on composition according to any of claims 1 to 15 wherein said solvent comprises a major part of 2-(2-butoxyethoxy)-ethanol.

17. A pour-on composition according to any of claims 1 to 15 wherein said solvent essentially consists of 2-(2-butoxyethoxy)-ethanol.

18. A pour-on composition according to any of claims 1 to 15 wherein said solvent comprises a major proportion of monoterpenes containing hydrocarbon and ether functions.

19. A pour-on composition according to any of claims 1 to 15 wherein said solvent comprises a major proportion of dimethyl sulfoxide.

20. A method of controlling parasites in non-human animals by applying to the skin or fleece of the animal by a pour-on or spot-on method a formulation according to any one of the preceding claims.

21. A method according to claim 20 wherein said animals are cattle.

22. A method according to claim 20 wherein said animals are sheep.

23. A composition substantially as described herein and with reference to the examples.

24. A method for controlling parasites in and on non-human animals as described and using the compositions exemplified and described.