NZ525112A - Anthelminthic formulation - Google Patents

Abstract

A stable liquid composition which comprises an effective amount of trichlorfon dissolved in a glycol based solvent, such as propylene glycol; and a method for treating or controlling endoparasites of a non-human animal which includes orally applying an oral formulation comprising the composition.

Description

New Zealand Paient Spedficaiion for Paient Number 525112 52S 1 f Patents Form No; 5 OurRef: JC218818 Patents Act 1953 COMPLETE SPECIFICATION ANTHELMINTIC FORMULATION We, AKZO NOBEL N.V., a body corporate organised under the laws of The Netherlands of Velperweg 76, 6824 BM Arnhem, The Netherlands, 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: -1- (followed by page 1a) PT05A10286 INTELLECTUAL PROPERTY OFFICE OF N.Z. " 2 APR 2003 RECEIVED 100129784J -1 a- Anthelminthic formulation The present invention relates to a stable liquid formulation of an anthelminthic and more particularly to a formulation having an organophosphate e.g. trichlorfon as 5 active ingredient.

Endoparasites commonly cause clinical disease in especially in livestock animals and have significant adverse economic effects on farming economies when present at subclinical levels. Anthelminthics, which control effectively important endoparasites, 10 but which offer improved human and environmental safety are a goal for animal production systems.

An example of a endoparasite is Haemonchus contortus. Haemonchus contortus is a blood sucking parasite and the development of clinical signs are related to the loss of 15 whole blood. In acute infections, where large numbers of larvae are ingested over a period of days, anaemia can cause death. In chronic infections, where the rate of infection has been slower, both anaemia and hypoalbuminaemia result from the loss of whole blood and the exhaustion of erythropoietic reserves.

Organophosphates are generally effective against Haemonchus, Trichostrongylus, Cooperia, Oesophagostomum and Dictyocaulus in sheep. They are active against Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Bunostomum and Oesophagostomum in cattle and against Gasterophilus (bots) in horses.

Trichlorfon is an organophosphate used as an insecticide and pesticide for plants 25 and livestock as well as an anthelmintic for animals.

The safety margin is very narrow, therefore exact dosing of the compound is necessary to avoid toxic reactions due to the application of higher dosages of trichlorfon. 3° One of the reasons for this is that the stable form of crystalline powder of trichlorfon breaks down in water if left for a relatively short period into the more toxic compound dichlorfos. The chemical stability of organophosphates such as trichlorfon is considerably impaired by the presence of water in formulations. It has been 35 established that trichlorfon re-arranges via dehydrochiorination to form dichlorfos Thus the organophosphate such as trichlorfon had to be mixed on site for immediate use and all material not used had to be safely discarded. This resulted in a labour-intensive preparation of the formulation that is to be applied to the animal and to higher costs for treatment and a need for safe discharge of not used material.

There has thus long been a need for a ready to use stable liquid solution of organophosphates such as trichlorfon and it is the object of the present invention to provide such a product or to at least provide the public with a useful alternative.

Trichlorfon (0,0-dimethyl-(2,2,2-trichloro-1-hydroxyethyl)-phosphonale)dimethyl 2,2,2,2-trichloro-1-hydroxyethyl-phosphonate , also called metrifonate is an organophosphorous compound having potent anticholinesterase activity and is administered topically as an ectoparasiticide or orally as an anthelmintic.

Examples of other organophosphates as antiparasitic agents are e.g. dichlorvos, coumaphos, crufomate or haloxon. Organophosphates act as cholinesterase inhibitor by irreversible inactivation of acetylcholinesterase, leading to excessive cholinergic activity at relevant sites.

In accordance with this invention there is provided a stable liquid composition for the treatment of endoparasites comprising trichlorfon that is dissolved in a glycol based solvent, preferably selected from propylene glycol, polyethylene glycol and glycerol formal. Propylene glycol is especially preferred.

Glycol based solvents such as polyethylene glycol, glycerol formal and propylene glycol are able to dissolve the active compound and produce a stable formulation. Such formulation may also be dispersed in water. Although a carrier material such as propylene glycol is relatively expensive, the low cost and effective active ingredient make the product desirably priced in relation to overall results.

The current invention further provides a process for preparing an anthelminthic formulation comprising the steps of dissolving the trichlorfon in the propylene glycol, in an example of this invention crystalline trichlorfon is dissolved in propylene glycol in a ratio of twenty grams per 100 ml or 200 grams /11 resulting in a final concentration of 20% m/v. The invention further provides for a solution of trichlorfon in a glycol based solvent.

The concentration of trichlorfon is between 10 and 30% w/v, preferably 15-25 %, most preferred approximately 20% w/v solution. With approximately is meant that for a 20% solution the concentration may vary by one percent either way based on the total volume of the composition.

This has been found to yield a stable solution over a considerable period of time. Trials (see Example 2) have shown a shelf life in excess of a year.

Optionally additional excipients such as colorants or thickening agents could be present in the composition according to the invention. Suitable pharmaceutical excipients are known in the art. Pharmaceutical excipients for oral liquid formulations are e.g. described in "Gennaro, Remington: The Science and Practice of Pharmacy" 10 (20th Edition, 2000), incorporated by reference herein.

A still further feature of the invention provides the solution to include a distinctive colorant, which is of food quality. Preferably a food grade colorant (e.g. Eurocert Green S, EC No. E142, EC name Green S, supplier Warner Jenkinson) is added to 15 the solution to give it a distinctive easily recognizable identification cover.

The composition and method of the invention may be used to treat a wide variety of endoparasites of animals.

The particular amount of the anthelmintic formulation required for a particular 20 treatment will vary, depending upon the species, age and weight of the animal being treated, the particular parasite to be guarded against, or treated, as well as the specific organophosphate compound selected for the treatment, the route and the frequency of administration. Anthelmintics are frequently delivered to ruminants in the form of oral drenches directly into the rumen.

The solution can be used against various endoparasites but is particularly effective against wire worm (Haemonchus contortus) and nasal grub (Oestrus ovis) in sheep. This parasite has become difficult to control and tests have shown (see Example 3) that the solution is effective where other widely used endoparasitics have not.

For example a suitable dosage of trichlorfon for oral administration for sheep is in the range between 30 to 110 mg/kg bodyweight (bw), preferably 40 to 100 mg/kg body weight, more preferred 45 to 80 mg/kg bw and most preferred 50 to 60mg/kg bodyweight.

A further aspect of the invention is an oral drench formulation comprising a composition according to the invention.

The oral drench formulation comprising the solution is supplied in pre-packed quantities to meet demand and is at all times in a ready to use condition. The product can be orally administered to sheep in a metered manner using a dosing gun (so called "drenching") and excess material may be stored for use at a later time.

The invention also provides a method of treating sheep against wire worm (Haemonchus contortus) infestation by the administration of a stored ready to use oral drench formulation comprising the solution as defined above.

In a further aspect the current invention concerns a method for treating or controlling endoparasites of an animal which includes orally applying to an animal a stable liquid composition according to the invention at a rate of 2 ml to 5 ml / 10kg, preferably 2.5 to 4.0 ml of the animal's live weight.

The method may be also be used to treat or control other endoparasites on a variety of animals including livestock animals as sheep, cattle, deer, goats, pigs, and companion animals as horses, dogs and cats.

In a further embodiment a composition according to the invention further comprises an additional anthelminthic compound e.g. ivermectin, abamectin, fenbendazole, levamisole, closantel, niclosamide, rafoxanide or mixtures thereof.

Example 1 Preparation of the solution Trichlorfon 20.0 %m/v Lime Green PBL 0517(Food Colourant) 0.0001 m/v Propylene glycol BP to: 100 /v Preparation a) Charge production tank with 70% of total batch size of propylene glycol b) Dissolve the trichlorfon into the propylene glycol while stirring the contents of the production tank vigorously with a suitable vortex mixer c) Dissolve the dye (lime green PBL 0517/ Eurocert Green S) into small proportion of the balance of the propylene glycol and add this solution to the production tank. Mix well d) Make the batch to volume with propylene glycol and again mix well.

Example 2 Stability test The product of example 1 (3 production batches) were stored at accelerated conditions for at least 9 weeks as well as at room temperature for the first 9 weeks and thereafter at 30°C for the following 40 weeks.

Results are shown in Table 1 below.

Table 1: Stability week Batch 1 Batch 1 Batch 2 Batch 2 Batch 3 Batch 3 room 44°C room 54°C room 44°C temp. temp. temp. 0 .59 .59 - - 2 21.54 19.98 - - 3 .19 19.23 .76 .89 19.84 17.88 .80 17.92 7 21.29 18.15 21.57 .61 9 .07 16.60 19.91 .31 11 21.11 21.20 21.32 week Batch 1 Batch 1 Batch 2 Batch 2 Batch 3 Batch 3 room temp. 44°C room temp. 54°C room temp. 44°C 13 19.85 .78 .37 21.88 19.51 19.86 17 19.98 .16 .34 19 .47 .45 .40 21 .40 19.62 19.88 23 .12 19.95 .40 .53 .41 21.00 27 19.86 19.64 .48 29 .13 18.98 .14 33 19.06 18.96 19.61 37 19.44 18.87 - 19.70 41 18.91 18.76 .27 45 19.19 18.49 .40 49 19.28 17.13 19.43 53 18.48 16.57 19.67 57 18.14 16.51 19.41 61 18.03 19.99 75 .42 17.72 79 11.27 14.30 All room temperature samples were placed on 30°C on week 13.

Example 3 Efficacy study The objective of the study was to evaluate the efficacy of trichlorfon 20% solution at various dose rates against anthelmintic susceptible adult and immature H. contortus (Onderstrepoort stain) in sheep. The study was conducted in two phases: Immature phase: Sheep (n=13) were infected with 1000 L3 H. contortus larvae (onderstrepoort strain) per os on Days -11, -8, -5 and -3. One untreated sheep was slaughtered on Day 0 as larval viability control to confirm the viability of the larvae dosed and to assess the development of the larvae. Sheep (n=3) were treated on Day 0 with trichlorfon (20% m/v) according to the invention at a dosage rate of 40 mg /kg bodyweight (bw), sheep (n=3), at 50 mg/kg bw, sheep (n=3) and at 60 mg/kg bw. Sheep (n=3) were left untreated serving as controls. All remaining sheep (n=12) were necropsied on Day +21 in order to allow the worms to develop to adults for easier worm recovery.

Adult phase: Sheep (n=13) were infected with 1000 L3 H. contortus larvae (onderstrepoort strain) per os on Days -21, -18, -15 and -12. One untreated sheep was slaughtered on Day 0 as larval viability control to confirm the viability of the larvae dosed and to assess the development of the larvae. Sheep (n=3) were treated on Day 0 with trichlorfon (20% m/v) according to the invention at a dosage rate of 40 mg /kg bodyweight (bw), sheep (n=3), at 50 mg/kg bw, sheep (n=3) and at 60 mg/kg bw. Sheep (n=3) were left untreated serving as controls. All remaining sheep (n=12) were necropsied on Day +14 in order to allow the worms to develop to adults for easier worm recovery.

Faecal Egg Counts (FEC) were performed on faeces collected from all sheep on the days of necropsy according to the method of Viser and Malan. Worm recovery was achieved by washing the ingesta thoroughly from the abomasal mucosa under a steam of water into a bucket. In addition, for the immature phase and the two larval viability controls the mucosal surface was scraped from the abomasum with a glass slide, placed in digestion fluid. The larvae and adult nematodes recovered were identified and counted.

Percentage control (Faecal Egg Count Reduction Test) and percentage efficacy (Worm Burden Reduction) values were calculated based on the untreated control group. The results are summarized in Table 2.

Results: The test formulation was found to be more than 99% effective (arithmetic reduction in worm burdens) against adult H. contortus at all three dosage rates (i.e. 40, 50 and 60 mg/kg bw).

The efficacy recorded against immature H. contortus increased from 80.56% (arithmetic reduction in worm burdens) at a dosage rate of 40 mg/kg bw to 95.52% at a dosage rate of 60 mg/kg bw (arithmetic reduction in worm burdens). The percentage efficacy against immature worms was 91.08% (arithmetic reduction in worm burdens) at a dosage rate of 50 mg/kg bw.

Claims (15)

Table 2 Percentage control and percentage efficacy values obtained using the faecal egg count reduction test and worm recovery at necropsy respectively Group Infection date Dose level mg/kg Faecal egg counts: percentage control Nematode recovery: percentage recovery A -11,-8, -5& -3 40 78.53 80.56 B -11,-8, -5& -3 50 88.64 91.08 C -11,-8, -5& -3 60 90.91 95.52 E -21,-18, -15, &-12 40 100.00 99.97 F -21,-18,-15, &-12 50 99.79 99.79 G -21,-18,-15, &-12 60 100.00 100.00 -9- Claims

1. A stable liquid composition which comprises an effective amount of trichlorfon dissolved in a glycol based solvent.

2. The composition according to claim 1 or claim 2 wherein the glycol based solvent is selected from propylene glycol, polyethylene glycol and glycerol formal.

3. The composition according to claim 3 wherein the glycol based solvent is propylene glycol.

4. The composition according to any one of claims 1 to 4 wherein the content of trichlorfon is between 10 and 30% weight / volume.

5. The composition according to claim 5 wherein the content of trichlorfon is approximately 20% weight / volume.

6. The composition according to any one of claims 1 to 4 wherein the composition additionally comprises a colorant.

7. An oral drench formulation comprising a composition according to any one of claims 1 to 6.

8. A method for treating or controlling endoparasites of a non-human animal which includes orally applying to a non-human animal an oral drench formulation according to claim 7.

9. A method for treating sheep against wire worm infestation which includes orally applying to an animal an oral drench formulation according to claim 7.

10. A method for treating sheep against wire worm infestation which includes orally applying to an animal a composition according to claim 6 or an oral drench formulation according to claim 7 at a rate of 2.5 ml to 4.0 ml / 10kg of the animal's live weight.

11. A stable liquid composition substantially as herein described with reference to Examples 1 to 3.

12. A stable liquid composition according to claim 1 substantially as herein described with reference to Examples 1 to 3. 100388521 1 -10-

13. A stable liquid composition according to any one of claims 1 to 6 substantially as herein described with reference to Examples 1 to 3.

14. A formulation according to claim 7 substantially as herein described with reference to Examples 1 to 3.

15. A method according to claim 8, claim 9 or claim 10 substantially as herein described with reference to Examples 1 to 3. 52 5 1 1 2 Abstract: The invention relates to a stable liquid formulation comprising an effective amount of trichlorfon dissolved in a glycol based solvent and its use for control of endoparasites in animals. INTELLECTUAL PROPERTY OFFICE OF N.Z. " 2 APR 2003 RECEIVED