WO2000031098A1

WO2000031098A1 - Injectable anthelmintic formulation

Info

Publication number: WO2000031098A1
Application number: PCT/KR1999/000704
Authority: WO
Inventors: Hoo-Kyun Choi; Se-Hoon Kim; Kyu-Boem Han; Byoung-Sun Chang
Original assignee: Lg Chem Investment Ltd.
Priority date: 1998-11-23
Filing date: 1999-11-22
Publication date: 2000-06-02
Also published as: NZ511852A; BR9915559A; AU753532B2; CN1354754A; MXPA01005123A; AU1584400A; KR100315465B1; CN1166676C; KR20000033304A

Abstract

Disclosed is an injectable anthelmintic formulation. The formulation includes a water-insoluble anthelmintic, a surfactant, cosolvent, water-soluble solvent and additives.

Description

INJECTABLE ANTHELMINTIC FORMULATION

CROSS REFERENCE TO RELATED APPLICATION

This application is based on application No. 98-50135 filed in the Korean Industrial Property Office on November 23, 1998, the content of which is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to an injectable anthelmintic formulation, and more particularly, to an injectable antheliminitic formulation with increased water solubility and bioavailibility of an active substance.

(b) Description of the Related Art

It is well known that ivermectin (or avermectin) is highly effective against both internal and external parasites located in a variety of mammals including cows, pigs, horses, etc. (R.W. Burg, et al., Antimicrobial Agents and Chemotherapy (1979) 361-367; J.C. Chabala, et al., J. Med. Chem. (1980) 23, 1134-1 136; J.A. Lasota, et al.. Annu. Rev. Entimol. (1991) 36, 91-1 17).

In order to stabilize and solubilize the invermectin (or avermectin), many injectable formulations have been developed and used today. Among them, two representative formulations are described hereinafter. In U.S. Patent No. 4,389,397 to Lo and Williams, ivermectin dissolves in water using a non-ionic surfactant such as polysorbate 80 (Tween 80), and the resulting mixture is stabilized with a cosolvent such as glycerol formal, propylene glycol, glycerine, or polyethylene glycol, and a substrate such as benzyl alcohol, lidocaine, parabens, or choline. According to this patent, ivermectin is able to be stabilized in an aqueous solution. However, no description of the pharmacokinetics and efficiency of the invermectin formulation in animal body are given in this application.

Further, in European Patent No. 535,734 A1 to Chen and Williams, a non-aqueous carrier such as hydrogenated castor oil or triacetin is used to increase the duration of ivermection in animal body up to 42 days. However, since this foumulation is an oil-based solution without water, the viscosity of the solution is almost 500 cps (centipoise; measured by Brookfield viscometer with a spindle #2 at 25 ^°C , 60 rpm) which is considerably higher than that of the typical water-soluble solution of ivermectin. Therefore, the major drawbacks of European Patent are difficulty of filtration and poor injectability. Other problem probably encountered during manufacturing this formulation includes the high power requirement to mix the solution at high rpm between 400 and 4000.

In the case where the non-aqueous solution is used as injectable, stability and solubility problems of ivermectin may be solved but following problems can be encountered: high viscosity; poor injectability; possibility of tissue damage or irritation where the injection is administered; precipitation of active components at the area of injection.

Accordingly, there is an increasing demand for better aqueous injectable formulation in which one of the insoluble anthelmintics, ivermectin or avermectin, is not only soluble while maintaining a stable state, but also quickly and efficiently absorbable in the animal body.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an injectable anthelmintic formulation with a high level of water solubility and enhanced bioavailibility.

It is an another object of the present invention to provide an injectable anthelmintic formulation with enhanced rate and efficiency absorption characteristics. These and other objects may be achieved by an injectable anthelmintic formulation. The injectable anthelmintic formulation includes a water-insoluble anthelmintic, a surfactant, a cosolvent and a water-soluble solvent. The formulation may further include additives such as an antioxidant and a preservative. The surfactant includes a block copolymer of ethylene oxide and propylene oxide.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawing, which is incorporated in and constitutes a part of the specification, illustrates an example of the invention, and, together with the description, serves to explain the principles of the invention:

FIG. 1 is a graph of comparing pharmacokinetics in swine between the formulation of the present invention and the commercially available Ivomec formulation (Merck & Co. INC. of the United States).

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a novel injectable anthelmintic formulation. The formulation includes a water-insoluble anthelimintic, a surfactant, a cosolvent and a water-soluble solvent. The formulation may further include additives such as an antioxidant and a preservative.

As the insoluble anthelmintic in the formulation of the present invention, it is possible to use ivermectin or avermectin, or derivatives thereof. The formulation includes from 0.5 to 2.0%(w/v) of ivermectin or avermectin, or derivatives thereof.

In the formulation of the present invention the surfactant and the cosolvent act as solubilizer. In other words, the surfactant and the cosolvent facilitate the water-insoluble anthelmintic to be dissolved in the water-soluble solvent. The surfactant may be a water-soluble copolymer that is listed in the pharmacopoeia. The water-soluble copolymer has both hydrophilic and hydrophobic properties. The water-soluble copolymer includes a block copolymer of propylene oxide (PO) and ethylene oxide (EO). The block copolymer has (EO)_x(PO)_y(EO)_x as a unit, where the ratio of x to y is between 0.75 and 2.0. The copolymer, which average molecular weight is between 9000 Da and 20000 Da, is presolubilized in water before use. The concentration of copolymer in water is between 5 and 25%. If the concentration of the copolymer is more than 25%, the viscosity of the mixed solution is increased and the solubility may be reduced. Whereas, the concentration thereof is less than 5%, the stability of the resulting injectable formulation is not guaranteed.

The cosolvent may be alcohol, and more preferably, ethanol. The concentration of cosolvent is from 1 to 50 % (w/v) in the formulation of the present invention. If the amount of the cosolvent is more than 50 %(w/v), the animals may feel a pain and stability of the resulting injectable formulation is reduced. Whereas, the amount thereof is less than 1 % (w/v), it is difficult to facilitate the water-insolube anthelmintic to dissolve in the water-soluble solvent. The water-soluble solvent may be water.

In addition, it is possible that the formulation of the present invention may contain a variety of additives such as an antioxidant and a preservative.

For example, it is possible to use butylated hydroxytoluene (BHT) as the antioxidant ranging from 0.001 to 0.5 % (w/v), and benzyl alcohol as the preservative agent ranging from 0.5 to 10 %(w/v).

For preparing the formulation of the present invention, it is possible to use a stepwise mixing method or a direct mixing method.

In the stepwise mixing method, ivermectin or avermectin is immediately dissolved in the solvent with additives. This solution is then added to another solution in which the surfactant is pre-dissolved in water, thereby producing the injectable formulation of the present invention. In the direct mixing method, all components of the formulation are simultaneously mixed together to produce the injectable formulation of the present invention.

The stepwise mixing method is preferable because the anthelmintic agent can be completely dissolved in the solvent for a short period of time, while the other direct mixing method needs more than 24 h to solubilize the anthelmintic agent completely.

In both methods, the pH of the solution is adjusted to 6.8 to 7.4 while the concentration of components in the injectable formulation is properly adjusted with water for injection. Finally, the prepared solution is sterilized by filtration.

The injectable formulation of the present invention prepared according to the above mentioned process remains stable for more than one year at both 4^°C and room temperature without any phase separation or precipitation.

Pharmacokinetics studies of the formulation of the present invention and commercially available Ivomec (Merck & Co., INC. of the United States) using swine show that the absorption rate of the formulation of the present invention to reach the concentration in blood is approximately twice faster than that of Ivomec (Merck & Co. INC. of the United States). However, the formulation of the present invention and Ivomec show similar degradation patterns. That is, the invermectin concentrations in blood for both cases are reduced to the same levels within 4 to 5 days and no significant differences between the two solutions are detected thereafter.

Since physical and pharmacokinetic properties of the injectable formulation of the present invention may vary according to the composition change of the present invention, the effects of ethanol concentration change in the formulation of the present invention on ivermectin solubility, viscosity of the formulation, and ivermectin pharmacokinetic were tested. It was showed that ivermectin solubility and viscosity of the formulation increase at high ethanol concentration. Furthermore, pharmacokinetc property was also changed depending on the ethanol concentration of the formulation. However, such changes were not so significant when they were compared with Ivomec's properties.

In conclusion, it was determined that a retention time of ivermectin in blood for the formulation of the present invention is almost identical to Ivomec, while the absorption of ivermectin in the present invention occurs approximately one day earlier than Ivomec and the absorption efficiency of the present formulation is roughly twice than that of Ivomec. In addition, it was observed that the tested animals experienced no abnormal changes with increased absorption efficiency of ivermectin. In other words, no toxicity or other side effects were observed among the tested animals as a result of the high absorption efficiency of ivermectin. These characteristics strongly indicate that the injectable formulation of the present invention is superior to the prior art, judging from its improved pharmacokinetic data.

In order to demonstrate, the efficacy of the present formulation for both endo- and ecto-parasites, efficacy tests were conducted using Ivomec as a control. Various swine including piglets, growing & finishing pigs (swine), and sows were used which wee artificially infected with Ascaris suum and Trichuris suis (endo-parasites), and Sarcoptes scabiei (an ecto-parasite). Test showed that the formulation of the present invention is either identical or superior to Ivomec.

In more detail, the parasite egg positive rate in growing & finishing pigs (swine) was reduced to 0% in 2 weeks after the treatment of Ivomec, while it took just 1 week using the formulation of the present invention. In case of growing & finishing pigs (swine) which were artificially infected, the parasite egg positive rates in one week after anthelmintic treatment started were as follows: 86% for Ascaris suum and 57% for Trichuris suis in no treatment groups; 80% for Ascaris suum and 0.0% for Trichuris suis in Ivomec group; 50% for Ascaris suum and 20% for Trichuris suis in the test group with the formulation of the present invention. These percentages decreased to 0.0% in two weeks in both treatment groups. The dead parasites were excreted between 1 and 3 days after the treatment with formulation of the present invention, while the killed parasites were observed between 1 and 8 days with Ivomec treatment. This is another good example showing the superior characteristics of the present invention for the removal of endo-parasites.

Meanwhile, removal of ecto-parasites in the piglets was also tested. The rate of pathological change for skin ailment in no treatment group was increased from 0.58 to 1.67 in 1 week and further augmented to 4.20 in 3 weeks after test started. However, in the piglets treated with the formulation of the present invention, the rate of pathological change for skin ailment was sharply decreased from 1.82 to 0.07 in 1 week and maintained at 0.13 after three weeks, which changes are quite similar to those rates of 1.06, 0.13 and 0.07 in case of the Ivomec treatment.

As shown in the above tests, the formulation of the present invention is at least equivalent or superior to Ivomec with respect to the pharmacokinetics and the efficacy as anthelmintic agent. Moreover, as described above, the present formulation is stable in aqueous phase for a considerable period of time without any physical changes such as phase separation or precipitation.

The present invention will be further described in details by the following examples. However, the invention can be utilized in various ways and is not intended to be confined to the following examples.

I. Manufacture of Ivermectin Injectable Solution Using Direct Mixing Method [Example 1]

2 ml of benzyl alcohol (Korean Pharmacopoeia grade) was added to a 300 ml flask which was p re-sterilized for 30 min at 121 ^°C . Followings were then added to the flask all at once: 0.01 g BHT (butylated hydroxytoluene, Korean Pharmacopoeia grade); 10 ml ethanol (Korean Pharmacopoeia grade); 70 ml water; 1.17 g ivermectin; 10 g Poloxamer 407 (BASF of Germany). Subsequently, a 5cm magnetic bar was introduced to the flask and stirred at 300 to 400 rpm. The resulting mixture became clear with the generation of bubbles therein, and completely clear solution was obtained after approximately 24 h stirring. Next, appropriate amount of water was added to the solution (at an amount to result in a desired final volume of the solution) to complete the mixing process and the solution underwent vacuum suction filtering using 0.2 μ of filter paper (Wattman Filter Paper of the U.S.), thereby producing a fully sterilized ivermectin injectable solution of 1%(w/v). A viscosity of the resulting solution was found to be 69 cps (centipoise; Brookfield viscometer spindle #CP-42, 6rpm) at room temperature.

[Example 2] Ivermectin injectable solution was prepared by the same procedure in

Example 1 except that 1 % (w/v) of ivermectin, 10.0 % (w/v) of poloxamer 407, 20.0 % (w/v) of ethanol, 0.01 % (w/v) of BHT, 2.0 % (w/v) of benzyl alcohol, and balance of water were used.

[Example 3] Ivermectin injectable solution was prepared by the same procedure in

Example 1 except that 0.5 % (w/v) of ivermectin, 10.0 % (w/v) of poloxamer 407, 15.0 % (w/v) of ethanol, 0.01 % (w/v) of BHT, 2.0 % (w/v) of benzyl alcohol, and balance of water were used.

[Example 4] Avermectin injectable solution was prepared by the same procedure in

Example 1 except that 1 % (w/v) of avermectin, 10.0 % (w/v) of poloxamer 407, 15.0 % (w/v) of ethanol, 0.01 % (w/v) of BHT, 2.0 % (w/v) of benzyl alcohol, and balance of water were used.

[Example 5]

Avermectin injectable solution was prepared by the same procedure in Example 1 except that 0.5 % (w/v) of avermectin, 10.0 % (w/v) of poloxamer 407, 15.0 % (w/v) of ethanol, 0.01 % (w/v) of BHT, 2.0 % (w/v) of benzyl alcohol, and balance of water were used.

II. Manufacture of Ivermectin Injectable Solution Using

Stepwise Mixing Method

[Example 6] First step: 10 g of Poloxamer 407 (BASF of Germany) was added to a

300 ml flask which was pre-sterilized for 30 min at 121 ^°C , followed by 70 ml water addition. Next, a 5cm magnetic bar was transferred into the flask and stirred at 300 to 400 rpm. Mixing continued approximately 70 min until the Poloxamer 407 was completely dissolved in water, thereby producing a clear first mixed solution. The first mixed solution was then filtered using a 0.2 μ filter and finally the resulting first solution having a viscosity at room temperature of roughly 9.75 cps (centipoise; Brookfield viscometer spindle #CP-42, 6rpm) was obtained.

Second step: Approximately 30 min later after the above first step of mixing process, a second mixing process was performed. Adding 2 ml of benzyl alcohol (Korean Pharmacopoeia grade) in a 25 ml flask which was pre- sterilized for 30 min at 121 ^°C , 0.01g of BHT (Korean Pharmacopoeia grade), 10 ml of ethanol (Korean Pharmacopoeia grade), and 1.17 g of ivermectin were transferred to the flask. Next, a 5 cm magnetic bar was transferred to the flask and stirred at 300 to 400 rpm. Mixing continued approximately 10 min until all the contents in the flask were dissolved, thereby producing a clear second mixed solution. The second mixed solution was then filtered using a 0.2 μ filter.

Third step: The first mixed solution and the second mixed solution were then transferred to a sterilized container and mixed for approximately 10 min to give a final mixed solution. Next, small amount of water was added to the final solution (at an amount to result in a desired final volume of the solution) to complete the mixing process, thereby producing a fully sterilized ivermectin injectable solution of 1%(w/v).

[Example 7] Ivermectin injectable solution was prepared by the same procedure in Example 6 except that 1.0 % (w/v) of ivermectin, 10.0 % (w/v) of poloxamer 407, 5.0 % (w/v) of ethanol, 0.01 % (w/v) of BHT, 2.0 % (w/v) of benzyl alcohol, and balance of water were used.

[Example 8] Ivermectin injectable solution was prepared by the same procedure in Example 6 except that 0.5 % (w/v) of ivermectin, 20.0 % (w/v) of poloxamer 407, 10.0 % (w/v) of ethanol, 0.01 % (w/v) of BHT, 2.0 % (w/v) of benzyl alcohol, and balance of water were used.

[Example 9] Avermectin injectable solution was prepared by the same procedure in Example 6 except that 1.0 % (w/v) of avermectin, 10.0 % (w/v) of poloxamer 407, 15.0 % (w/v) of ethanol, 0.01 % (w/v) of BHT, 2.0 % (w/v) of benzyl alcohol, and balance of water were used.

[Example 10] Avermectin injectable solution was prepared by the same procedure in Example 6 except that 0.5 % (w/v) of avermectin, 10.0 % (w/v) of poloxamer 407, 15.0 % (w/v) of ethanol 0.01 % (w/v) of BHT, 2.0 % (w/v) of benzyl alcohol, and balance of water were used.

The injectable formulations produced in the above Examples as described underwent various tests as described hereinbelow.

[Test 1] Pharmacokinetics Comparison Tests Between Injectable Formulation of the Present Invention and

Ivomec (Merck & Co. INC. of the United States) The injectable formulation was manufactured according to the method of Example 6. It consists of 1.0% of ivermectin, 10.0% of Poloxamer 407, 15.0% of ethanol, 2.0% of benzyl alcohol, 0.01 % of BHT, and sterilized water making up the remaining portion of the solution. The formulation of the present invention and Ivomec were injected in two separate test groups of growing & finishing pigs (swine) at an amount of 300 μg per kilogram body weight. Next, blood samples were taken at every predetermined time. The blood samples were then centrifuged for 20 min at 3000 rpm to separate the plasma from the blood, after which the plasma was stored at -20°C. In order to analyze a pharmacodynamics of the two tested formulations in pigs, the plasma samples were thawed and assayed using a modified method of Montigny's fluorescence derivatization-HPLC analysis method (J. Pharm. Biomed. Anal. (1990)_8, 507- 511).

After adding 1 ml acetonitrile to 1 ml of each plasma sample, the resulting mixtures were centrifuged for 10 min at 3000 rpm. The supernatant was then subjected to solid phase extraction. That is, in solid phase extraction, the samples were treated with in Sep-Pak C18 cartridges (Waters of the U.S.). After the cartridges were fully dried with nitrogen gas, the purified samples were slowly eluted with 5ml chloroform and then dried up using nitrogen gas.

Subsequntly, each dried sample was dissolved with 100 μl of 1- methylimidazole: acetonitrile mixture (1:2, v/v) and 150 μl of trifluroacetic anhydride: acetonitrile mixture (1 :2, v/v) was added thereto such that the ivermectin isolated was derivatized for better measurement. 100 μl of this derivatized solution was then analyzed with HPLC (TSO P1000, U.S.A) with a fluorescence detector (TSP F3000, U.S.A.). Peak measurement was done under a 374 nm excitation wavelength and a 475 nm emission wavelength conditions. 0.2% of acetic acid-methyl alcohol-acetonitrile mixture at a volume ratio of 4:32:64 was used for a mobile phase in Nova-Pak C18 (4 μ , 3.9 X 150 mm, Waters, U.S.A.), and a mobile phase flow rate was 1.5 ml/min.

A concentration of the ivermectin in the samples was determined by comparing HPLC peak area of the plasma samples from the pigs injected by the present formulation and Ivomec, with standard curve prepared by addition of 0.5, 5, and 50 ng of ivermectin (Sigma, U.S.A.) to 1 ml of plasma taken from the pigs not treated with any anthelmintic. The treatment and measurement of the samples were simultaneously performed without any delay and blood samples taken from one pig were analyzed all at once. To reduce variation errors in pre- treatment of samples, standard samples were simultaneously prepared and used every time of analysis. At this time the peak of derivatized ivermectin B1a derivative appeared at about 10 min retention time in HPLC. Also a small peak appeared at about 8 min, which represents ivermectin B1 b derivative.

The concentration of ivermectin in blood samples was determined by comparing combined areas of two peaks with those of ivermectin peak areas in the standard curve. Everytime the analysis was performed, standard blood sera were prepared by adding different concentrations of ivermectin and treated with the same method as for the test sample treatment. These newly prepared standards were used to determine the concentration of the test samples. The standard curve equation (linear regression equation) between ivermectin concentrations and HPLC peak area was: area = 1.729 x 10^"4 x ivermectin concentration + 0.10039; and a linear regression coefficient (R²) was

0.998. Using this linear equation, the ivermectin concentrations in the blood samples were determined and the results of which for both the formulation of the present invention and Ivomec are shown in FIG. 1.

As shown in the drawing, the maximum concentration of ivermectin in plasma samples from pigs injected with the formulation manufactured according to Example 6 is twice higher than that of Ivomec. However, 4 or 5 days later after injection, concentrations of ivermectin for both the present formulation and Ivomec are substantially reduced to equal levels.

Such a different pharmacokinetics of ivermectin is because of the composition difference between Ivomec and the formulation of the present invention. Compared with the Ivomec, the formulation of the present invention is more quickly absorbed in the blood and shows superior pharmacodynamic property. This suggests that, when identical amounts of ivermection are used, the ability of the formulation of the present invention to kill parasites is significantly better than that of Ivomec.

[Test 2] Comparasion Tests of Injectability Between Injectable Formulation of the Present Invention and Other Various Commercial Products Containing Ivermectin

An injectability comparison test was performed using the injectable formulation of the present invention (I), Ivomec (Merck Co.) (II), Ivomec-F (Merck Co.) (Ill), Baymec (Bayel Co.) (IV), Abamec (Daesung, Korea) (V), and Dectomax (Pfizer) (VI).

3 ml of each above formulation was transferred to a Greenject-5 (5 ml) syringe (Green Cross Pharmaceutical Corp., Korea, 23 gauge, 1") and average injectability values were compared using an injectability measurement device (Test Stand Model-2252, CPU Gauge Model 9500, AIKOH Engineering Co., Ltd., Japan). The values are shown in Table 1 below. As shown in the table, the injectability value of formulation II (Ivomec) was the lowest at 0.53 kg, while the value of formulation IV (Baymec) was the highest at 1.73 kg. The injectability value for the formulation of the present invention, formulation I was approximately in between the highest and lowest values. In conclusion, the force needed during injection of the present formulation is similar to that of typical product in the market.

Table 1

[Test 3] Viscosity Measurement Ivomec and the Formulation of the Present Invention Containing Different Concentrations of Ethanol

We have studied how physical characteristics such as viscosity and solubility of the formulation of the present invention vary according to the composition change of special component. For viscosity test, a variety of the formulations of the present invention with different concentrations of ethanol (5,

10, 15, and 20%) were prepared according to the method of Example 6.

Using a Brookfield Visometer (spindle # CP-42, 6 rpm, 25°C), viscosities of the present formulations and Ivomec were measured. The results are shown in Table 2 below. As shown in the table, the viscosity of the present formulation increases with increase of ethanol level. The time to reach a clear solubilization of all components increases as the concentration of the ethanol decreases.

Table 2

[Test 4] Pharmacokinetics of Ivomec and the Formulation of the Present Invention Containing Different Concentrations of Ethanol

The formulation of the present invention manufactured according to Example 6 and Ivomec were injected to two separate test groups of growing & finishing pigs (swine) at an amount of 300 μg per kilogram of body weight. Blood samples were taken at predetermined time intervals after the injection and using the method described in [Test 1], ivermectin concentration changes in the blood were measured. The results are shown in Table 3 below. As shown in the table, average maximum concentrations of ivermectin in the blood are ranged from 1.7 to 2.1 -times of that for Ivomec and the time for Ivomec to reach its peak is 36 h, while the formulation of the present invention takes 2 to 5 h depending on the amount of ethanol in the present formulation.

Although it is not shown in Table 3, the reduction rate of ivermectin concentration after the peak seems to be correlated with the increase of ethanol level in the formulation. When ethanol content is less than 10%, the reduction of ivermectin concentration in case of the formulation of the present invention is almost identical to that in case of Ivomec in 5 days.

Table 3

As shown from the above, we can recognize that the results of both [Test 1] and [Test 5] are similar. That is, the absorption rate of the formulation of the present invention is approximately twice higher than that of Ivomec. In addition, the reduction rate of ivermectin concentration in the blood of the formulation of the present invention is slower than that of Ivomec so that the maintnenance of the ivermectin concentration in the blood by the present formulation is nearly identical to that by Ivomec. These results suggest that identical amounts of ivermectin are used, the formulation of the present invention can be more effective to kill parasites (it is proved by [Test 5]).

Since the above characteristics were not tested in case where an excessive amount of ethanol (over 20%) is used, it is preferable to use less than 20% ethanol in the present formulation.

[Test 5] Efficacy in Tests against Endo and Ecto-Parasites with Ivomec and the Formulation of the Present Invention Containing Different

Concentrations of Ethanol For the efficacy test against endo-parasites, sows and growing & finishing pigs infected with Ascaris suum and Trichuris suis were used, and for the efficacy test against ecto-parasites, piglets infected with Sarcoptes scabiei were used. Each pig was injected with Ivomec or the present formulations (0.3 mg/kilogram of body weight). Feed and water to the test pigs were provided in normal pattern and amount according to the schedule in local pig farms. 40 piglets were artificially infected with Ascaris suum (100 infectious eggs) and Trichuris suis (100 infectious eggs). Infection was made twice in two weeks period. After artificial infection, any excreted egg was inspected every day. The test results are described below. (5-1) Efficacy and safety tests with growing & finishing pigs Test results of artificially infected growing & finishing pigs showed that parasitic eggs positive rates, one week after test started were as follows: 0% for the formulation of the present invention; 0% for a double dosage of the present formulation; 17% for Ivomec; and 33% for the control group of untreated pigs. After 2 weeks, the parasitic egg positive rates for al! pigs treated with the formulation of the present invention and Ivomec became 0%, whereas the percentage for the control group of pigs increased to 50%.

A parasitic egg reduction was 100% for the pigs treated with either Ivomec or the present formulation, while it was 0% for the untreated control group of pigs. An excretion of dead parasites was 0% for the control group of pigs, while it was between 23.3 and 26.7% for the pigs treated with Ivomec or the formulation of the present invention. Further, in all of treated pigs, no abnormalities in the area of injection (e.g., fever, inflammation) and unusual behavior were observed. Table 4

"Inspection of parasitic eggs and severity of diarrhea were performed before treatment and 1 , 2, and 3 weeks after treatment, survival rate was observed over the entire period, and excretion of dead parasites was observed everyday until parasites were no longer excreted (5-2) Efficacy test with artificially infected growing & finishing pigs

The excretion of dead parasites was observed between the first and third days among the pigs injected with the formulation for the present invention, whereas among the pigs injected with Ivomec, dead parasites were excreted between 1^st and 8^th days after treatment. Five weeks after the treatment of anthelmintic agents all the pigs underwent post-mortem examination to check the existence of parasites. A few parasites were observed in the small intestine of the untreated pigs, while no parasite was detected in the pigs treated with the formulation of the present invention. Furthermore, to check the efficacy of the present formulation against Ascaris suum, the pigs at the time of treatment and roughly 1-5 five weeks prior to treatment were artificially infected with approximately 100 larvae. No larvae were observed among the pig tested, suggesting that the formulation of the present invention is also effective to kill this parasite. In addition, no abnormalities in the area of injection (e.g., fever, inflammation) and unusual behavior were observed among the pigs tested. No injection marks or inflammation in the area of injection were detected during post-mortem examination.

Table 5

Injection amount of the present formulation X 2: 0.6 mg/kg body weight (5-3) Efficacy test in growing & fiinishing pigs artificially infected with the endo-parasite, Ascaris suum

Three test groups of pigs were artificially infected with Ascaris suum. At the start of the test, Ascaris suum eggs were detected in all of the pigs of every test group. However, after one week, it was shown that the control group of untreated pigs had an egg positive rate of 86%, the group of pigs treated with the formulation of the present invention had the rate of 40-50%, and the group of pigs treated with Ivomec had the rate of 80%. Between 2^nd and 5^th weeks, the egg positive rate of control group was between 86 and 100%, whereas in the groups treated with either Ivomec or the formulation of the present invention, a 0% egg positive rate was observed, which means that all the parasites were terminated (see table 6).

Table 6

The feces of pigs tested were examined and it was observed that 100 to 10,560 Ascaris suum eggs per 1g (EPG; egg/gram) of feces were detected at the beginning of the test. Among the pigs treated with either Ivomec or the formulation of the present invention, the number of parasite eggs detected in feces dropped significantly after the first week, with the no eggs being detected after two weeks. However, parasite eggs were continuously observed in control group of pigs. The results of this test are shown in Table 7 below.

Table 7

(5-4) Efficacy test in growing & finishing pigs artificially infected with the endo-parasite, Trichuris suis

Three test groups of pigs were artificially infected with Trichuris suis. At the start of the test, a egg positive rate was between 29 and 100% for this parasite. After one week, it was determined that the control group of untreated pigs had an egg positive rate of 57%, the group of pigs treated with he formulation of the present invention had an egg positive rate of 20%, and the group of pigs treated with Ivomec had 0% rate. From 2 to 5 weeks after treatment, the egg positive rate of control group was between 0 and 86%, but in the groups of pigs treated with either Ivomec or the formulation of the present invention, no Trichuris suis eggs were detected. Table 8 below outlines the results of this test.

Table 8

The feces of pigs tested were also examined. From 0 to 215 Trichuris suis eggs per 1g (EPG; egg/gram) of feces were detected. Up to three weeks, Trichuris suis eggs were detected in the feces of the control group of pigs, while the number of Trichuris suis eggs in feces of the groups treated with the present formulation or Ivomec decreased significantly after one week and no eggs being detected after two weeks. The results are shown in Table 9 below.

Table 9

(5-5) Efficacy test against ecto-parasites in piglet

Piglets were used to conduct the efficacy test of the present formulation against the ecto-parasite, Sarcoptes scabiei. In the control group of untreated piglets, the rate of skin pathological change at the start of test was 0.58, and increased to 1.67 after one week and further increased to 4.20 after three weeks. In the group of piglets treated with the formulation of the present invention, the rate of skin pathological change was reduced from 1.82 to 0.7 after one week and further decreased to 0.13 after three weeks. In the group of piglets treated with Ivomec, the rate of skin pathological change was reduced from 1.06 to 0.13 after one week and 0.07 after three weeks. Test results are shown in Table 10. Table 10

(5-6) Efficacy test against endo and ecto-parasites in sow

Sows were used to conduct the efficacy test of the present formulation against the endo and ecto-parasites. No diarrhea was seen among the sows tested at 1 , 2 and 3 weeks. Dead parasites were detected in the feces of the sows injected with the formulation of the present invention after two days and no more parasites were found after 7 days. In the case where the sows were treated with Ivomec, the parasites begun to be excreted after three days and were no longer detected after 8 days. Further, with regard to ecto-parasites, all the parasites were removed in the sows treated with either the present formulation or Ivomec, whereas no significant improvement was detected in the untreated control group of sows.

In addition, in all of treated sows, no abnormalities in the area of injection (e.g., fever, inflammation) and unusual behavior were observed. The treated sows were also examined during post-mortem examination. No marks or infection were detected in the injection area. The results of this test are shown in Table 11 below.

Table 11

The formulations of the present invention as described above are extremely stable in aqueous phase and do not undergo phase separation. Further, as shown in a number of clinical tests, the formulations of the present invention have a better pharmacokinetic property and an equivalent or better efficacy against both endo and ecto-parasites than the prior art. Other physicochemical properties of the formulations of the present invention include their long stability, similar viscosity, and injectability compared to the prior art. Finally, no physical damage or other side effects were observed in the area of injection with the use of the present formulation.

While the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that various modifications and substitutions can be made thereto without departing from the spirit and scope of the present invention as set forth in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An injectable anthelmintic formulation comprising: an water-insoluble anthelmintic; a surfactant comprising a block copolymer of ethylene oxide (EO) and propylene oxide (PO); a cosolvent; and a water-soluble solvent.

2. The formulation of claim 1 wherein the insoluble anthelmintic is selected from the group consisting of avermectin, ivermectin and derivatives thereof, and is included in the formulation in a range from 0.5 to 2.0% (w/v).

3. The formulation of claim 1 wherein the surfactant is contained in the formulation in a range from 5 to 25% (w/v).

4. The formulation of claim 3 wherein the cosolvent is ethanol, and is contained in the formulation in a range from 1 to 50% (w/v).

5. The formulation of claim 1 further comprising additives.

6. The formulation of claim 5 wherein the additives include 0.001 to 0.5%(w/v) of butylated hydroxytoluene and 0.5 to 10%(w/v) of benzyl alcohol.

7. The formulation of claim 1 wherein the block copolymer is a (EO)_x(PO)y(EO)χ unit, where the ratio of x to y is in a range from 0.75 to 2.0 and the average molecular weight is between 9000 Da and 20000 Da.

8. The formulation of claim 1 wherein the anthelmintic is used to terminate both endo and ecto-parasites.