WO2000050009A1

WO2000050009A1 - Methods for administering pharmacologically active compounds to vertebrates

Info

Publication number: WO2000050009A1
Application number: PCT/US2000/004870
Authority: WO
Inventors: William R. Campbell; Douglas I. Hepler
Original assignee: Idexx Laboratories Inc
Current assignee: Idexx Laboratories Inc
Priority date: 1999-02-26
Filing date: 2000-02-25
Publication date: 2000-08-31
Anticipated expiration: 2001-08-26
Also published as: AU3606100A

Abstract

The present invention relates to methods of administering water labile and/or water insoluble, pharmacologically active compounds to vertebrate animals comprising encapsulating the compound in liposomes and administering the liposomes in the drinking water of the animal. The pharmacologically active compound may be a parasiticide, such as ivermectin, an antibiotic, a nutrient, a growth control compound, or other compounds. Methods are also provided for stabilizing water-labile pharmacologically active compounds and for solubilizing water-insoluble pharmacologically active compounds.

Description

METHODS FOR ADMINISTERING

PHARMACOLOGICALLY ACTIVE COMPOUNDS TO VERTEBRATES

FIELD OF THE INVENTION

The present invention relates to methods of administering water labile, pharmacologically active compounds to vertebrates . The methods may involve the administration of ivermectin-containing liposomes to the drinking water of the vertebrate to treat a parasitic infection. The methods are useful for treating roundworms, cecal worms, lice, ticks, capillarial worms, and mite infections. The present invention also generally relates to methods of stabilizing water-labile pharmacologically active compounds in aqueous solutions by encapsulating the drug compounds in liposomes.

BACKGROUND Parasitic infections are common problems in a variety of vertebrates, including cattle, horses, swine, sheep, caprines, and fowl. Various parasitic infections are also problematic in companion animals such as dogs and cats. Chickens and other fowl are known to suffer from a variety of parasitic infections. Roundworms, cecal worms, capillarial worms, lice, and mites are among the common parasites associated with fowl and exact a substantial economic cost from the producers of fowl each year and raise health issues regarding the safety of the food supply. Common methods of eliminating these parasites from fowl include the administration of piperazine to the drinking water or feed of animals. This method has had limited success due to the limited effectiveness of piperazine against these parasites. Administration of tramisol in a similar manner has had somewhat better success but its use is limited by its very high cost. Therefore, animal caretakers are still in need of a cost-effective, efficacious method of eliminating these parasites. Mezei et al . , U.S. Patent No. 4,761,288, which is hereby incorporated by reference in its entirety, describe a multiphase drug delivery system which contains a composition of multilamellar lipid vesicles with a slightly water soluble biologically active compound, a saturated solution of the biologically active compound, and the biologically active compound in solid form. Mezei et al . also describe the preparation of these compositions.

Mezei et al . , U.S. Patent No. 4,897,269, which is hereby incorporated by reference in its entirety, also describe methods of topically administering their compositions to deliver the biologically active compound. However, this delivery method, and others known in the art, can not be practically applied to administering pharmacologically active compounds to large numbers of fowl or other production animals since it requires that each bird be individually handled and treated, resulting in unreasonable costs and expenditures of time for large scale animal production facilities. SUMMARY OF THE INVENTION

The present invention provides methods of administering pharmacologically active compounds to vertebrates. The methods involve encapsulating the pharmacologically active compound in liposomes to form a liposome composition and administering the liposome composition to the drinking water of the vertebrate. The vertebrate may be a bovine, equine, ovine, feline, canine, porcine, a caprine, or a fowl. In a preferred embodiment, the animal may be a fowl. The pharmacologically active compound may be a parasiticide which is water labile and/or water insoluble and may be ivermectin. The ivermectin may be administered to treat a parasitic infestation in the vertebrate and may be present in the liposome composition at a concentration of from about 0.01% to about 2.5% (w/v) drug in solution. In a preferred embodiment, the ivermectin may be present in the liposome composition at a concentration of from about 0.1% to about 2.0% (w/v) drug in solution.

The ivermectin may be present in the drinking water at a final concentration of about 10 parts per million or greater, or from about 10 ppm to about 1500 ppm. In a preferred embodiment, the ivermectin may be present in the drinking water at a final concentration of from about 10 ppm to about 500 ppm. In various embodiments, the parasites may be roundworms, mites, cecal worms, capillarial worms, lice, or ticks. In other embodiments the pharmaceutical may be any of a wide range of antibiotics, nutrients, growth regulators, and other compounds including but not limited to, those described herein and the salts thereof.

The present invention also discloses a method of stabilizing a water-labile pharmacologically active compound in aqueous solutions which comprises encapsulating the water-labile pharmacologically active compound in a liposome to enhance its stability in aqueous solutions.

Compounds which may be stabilized by these methods include, but are not limited to, all of the compounds mentioned herein. In various other embodiments, these compounds may also include nutrients and growth regulators such as vitamins, including vitamins A, E, D, and K, and steroid hormones and their derivatives, such as estrogen and estradiol .

The present invention also discloses a method of increasing the water solubility of a water insoluble pharmacologically active compound which comprises encapsulating the pharmacologically active compound in a liposome to increase its solubility in aqueous solutions.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to methods of administering pharmacologically active compounds to vertebrates. The methods involve encapsulating the pharmacologically active compound in liposomes and administering the liposomes to the drinking water of the vertebrate .

In a preferred embodiment, the pharmacologically active compound may be a water labile compound and may be a parasiticide or an anti-parasitic agent, and the vertebrate may be a fowl. In a more preferred embodiment, the parasiticide or anti-parasitic agent may be ivermectin which may be present in the drinking water, encapsulated in liposomes, at a concentration of from about 0.01% to about 2.5% (w/v) drug in solution. In a particularly preferred embodiment, the ivermectin may be present in liposomes and present in the drinking water at a concentration of from about 0.1% to about 2.0% (w/v) drug in solution. The ivermectin may also be present in the liposomes and present in the drinking water at a final concentration of greater than about 10 ppm (w/v) drug in solution. In preferred embodiments, the ivermectin may be present at final concentrations in the water of from about 10 ppm to about 2000 ppm drug in solution. While most of the ivermectin will be encapsulated within the liposomes, there will remain a portion of the ivermectin which is located in between liposomes and not encapsulated at all. Therefore, the concentrations cited herein relate to drug present in solution and not solely to the concentration of ivermectin in the liposomes. As used here, "parasiticide" means any ectoparasiticide, acaricide, miticide, pediculicide, and antihelminthic . As used here, "anti-parasitic agent" means a miticide or an antihelminthic, including but not limited to ivermectin. As used here, "miticide" means any composition which is harmful to mites. As used here, "antihelminthic" means any composition which is harmful to any species of helminth.

As used here, "water labile" means that the pharmacologically active compound has a tendency to lose its pharmacological effectiveness in aqueous solutions. As used here, "water insoluble" means that the pharmacologically active compound generally shows resistance to solubilization in aqueous solutions. Compounds which are water insoluble may nevertheless still have some significant level of solubility in aqueous solutions . It is known that unmodified ivermectin cannot be efficiently administered in the drinking water because of its chemical instability and insolubility in water. Ivermectin in aqueous solutions is chemically degraded and loses its pharmacological efficacy before its therapeutic effect can be realized.

We have discovered that when ivermectin is encapsulated in liposomes, it is stable in aqueous solutions for periods of time of at least 10 days. As a result, it is both very practical and efficient to administer liposomes containing ivermectin in the drinking water of fowl and other vertebrates for the elimination of parasitic infections.

Without being bound by any particular theory or principle, it is believed that the surprising stability of ivermectin in liposomes is attributable to chemical attractions occurring within the liposome between ivermectin and the lipid members of the liposome . These chemical attractions are believed to stabilize the ivermectin molecule. While encapsulation within a liposome may provide some protection for the ivermectin molecule from water, it is believed that some water nevertheless enters and/or travels through the liposome, such that the ivermectin is still exposed to a substantial amount of water, even within the liposome. This presence of water makes the observed effect even more unexpected.

Therefore, one may stabilize, or increase or enhance the chemical stability of, pharmacologically active, water- labile compounds in aqueous solutions by encapsulating them in liposomes. This invention makes it possible for water- labile compounds in general to be conveniently administered in drinking water since their stability in aqueous solutions will be dramatically extended. Similarly, compounds which can not be efficiently administered in drinking water due to their insolubility in aqueous solutions may be administered in the drinking water in these liposomes. It was also unexpectedly discovered that the liposomes of this invention remain in solution at low concentrations and do not tend to aggregate towards the bottom of the water container. Without being bound by any particular theory, it is believed that the combination of the lower specific gravity of these liposomes relative to water, which is due to the low concentration of ivermectin, combined with repelling forces which exist between the liposomes, serve to keep these liposomes suspended relatively uniformly in the water and to prevent their aggregation. This enables the liposomes to be administered in the drinking water to provide a steady dose of pharmacologically active compound to the treated animal.

The present invention derived from the unexpected discovery that the encapsulation of ivermectin in liposomes results in a water-stable drug product which may be easily and conveniently administered to the drinking water of a vertebrate, and which requires no further effort thereafter to complete the therapy. The present invention will make newly available a number of compounds to treat a variety of animals for a variety of illnesses or infections. These compounds formerly could not be effectively used due to their lability and/or insolubility in aqueous solutions.

The present invention may be applied to a wide variety of compounds, and it is especially contemplated that the present invention may be applied to various nutrients and growth promoters. For example, by applying the present invention, vitamins A, E, D, and K (which are lipophilic and therefore do not dissolve readily in water) may be efficiently administered in drinking water since the solubility of these compounds will be enhanced by incorporation in liposomes. Similarly, hormones and their analogs, such as estradiol and other estrogen derivatives, or other steroid compounds, may be incorporated into liposomes and administered in the drinking water of the animal in a cost-effective manner with great ease.

It is preferred that the pharmacologically active compound of interest to be applied in the present invention be a molecule which is chemically attracted to lipids (lipophilic) , as these molecules are expected to most clearly demonstrate the benefits described herein. The molecule of interest should also have some significant level of solubility in water (i.e., not be completely water insoluble) .

The person of ordinary skill will realize that the present invention may be applied to encapsulate the following compounds in liposomes for administration in the drinking water: doramectin, avermectin, abamectin, milbe ycin, amprolium, bacitracin, chlortetracycline, erythromycin, lincomycin/spectinomycin, neomycin, oxytetracycline, piperazine, sarafloxacin, spectinomycin, sulfachloro-pyrazine, sulfadimethoxine, sulfamethazine, sulfaquinoxaline, tetracycline, and tylosin. These compounds, which may be difficult to administer in the drinking water due to their lack of solubility in water, are provided as exemplary and are not intended to be limiting. The named compounds are meant to encompass their salt forms as well.

The unmodified salt forms of these compounds may exhibit improved solubility, but still not be able to be administered in the drinking water due to their water lability. The present invention may serve to increase the water stability of these water labile compounds and/or serve to increase the water solubility of water insoluble compounds .

The person of ordinary skill will identify other compounds, both existing and yet to be discovered, which may be utilized in the present invention and which are meant to be encompassed within the scope of the present invention. We here show the complete elimination of parasites such as roundworms, cecal worms, and fowl mites from chickens by applying ivermectin in the present invention which may be conveniently administered to the drinking water and which requires no further effort, since the compound's stability and potency in water is maintained for at least 10 days. The present invention may also be useful for treating a variety of other parasitic infections such as ticks and lice.

The application of present invention is illustrated through the following examples. These examples are not intended to be limiting and the person of ordinary skill will realize that these methods may be applied to administer a variety of pharmacologically active compounds to treat various illnesses and infections in a variety of animals, including cattle, horses, swine, sheep, goats, and fowl.

Example 1

This example illustrates how the present invention was applied to eliminate poultry roundworms (Ascaridia) in chickens. Eight Silver Wyandot chickens were used in the study. The liposome composition was prepared according to the methods of Mezei et al . and contained ivermectin encapsulated in liposomes such that a final concentration in the drinking water of 0.1% ivermectin (w/v) was achieved. The chickens were placed into four groups of two and the composition was administered in the drinking water at concentrations of 0 ppm, 100 ppm, 250 ppm, and 500 ppm (w/v) ivermectin in the drinking water. The level of infestation was determined by comparing roundworm egg counts before therapy, at 24 hours, and at 48 hours. At the end of the study a necropsy was performed and roundworms that remained in the intestine were counted. The results are summarized in Table 1.

Table 1

Roundworm Egg Counts

Worm Count

Dose Pretest 8 hour 24 hours at 48 hours

0 6-20 21 14 3 0 6-20 11 6 1 100 >20 8 11 0 100 6-20 0 0 0 250 6-20 0 0 0 250 6-20 1 0 0 500 >20 59 0 0 500 6-20 0 0 0

By the end of 48 hours, the roundworms had been completely eliminated from the digestive tracts of the chickens treated with drinking water containing 100 ppm (w/v) (about 4.0 mg/kg of body weight/day) or greater drug in solution of ivermectin encapsulated in liposomes. It was also determined through additional testing that dosing could be done as low as 50 ppm (w/v) and still resulted in the elimination of the roundworms from the chickens within 48 hours . Example 2

This example illustrates how the present invention was used to treat northern fowl mites in chickens . Eight chickens were randomly assigned to four groups, with two chickens per group. The 0.1% ivermectin encapsulated in liposomes composition was administered to the drinking water of each group at dosages of 0 ppm, 100 ppm, 250 ppm, and 500 ppm (w/v) ivermectin in the drinking water (i.e., drug in solution) . It was determined that at 500 ppm (or 78.5 mg/kg of body weight/day), 0.1% ivermectin in liposomes completely eliminated fowl mites within 24 hours.

Example 3 This example illustrates how the present invention was applied to eliminate roundworms, cecal worms (Heterakis) , and fowl mites in 70 week+ White Leghorn hens. Ivermectin encapsulated in liposomes was added to 10 liters of drinking water such that a final concentration of drug in solution ranged from 10 ppm to 200 ppm. The animals were placed in a cage setting and allowed to drink ad-lib for 48 hours. The birds were heavily infested with cecal worms at the start of the study and the infestation had proved difficult to remove by currently used methods such as by using piperazine or tramisol. At the end of 48 hours of therapy with ivermectin liposomes in the drinking water, the following conclusions were drawn. Roundworms were easily removed at dosages as low as 10 ppm (or 2.75 mg/kg of body weight/day) in only a 24 hour exposure (see Example 1) . Fowl mites were removed beginning with dosages of 500 ppm (or 78.5 mg/kg of body weight/day) after 48 hours of exposure. 200 ppm (or 55 mg/kg of body weight/day) was sufficient to completely remove cecal worms in a 48 hour period. The birds exhibited no adverse reactions to the therapy at any dosage level. Birds continued to eat, drink and lay eggs normally while on treatment .

CLOSING It must be noted that as used herein and in the appended claims, the singular forms "a," "and" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a method of treatment" includes reference to equivalent steps and methods known to those skilled in the art, and so forth. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs .

Additional embodiments of the invention are described in the following claims.

Claims

What is claimed is:

1. A method of administering a pharmacologically active compound to a vertebrate, comprising: encapsulating the pharmacologically active compound in liposomes to form a liposome composition; and administering the liposome composition to the drinking water of the vertebrate.

2. The method of claim 1 wherein the pharmacologically active compound is water labile and/or water insoluble.

3. The method of claim 1 wherein the' pharmacologically active compound is a parasiticide for the treatment of a parasite infection.

4. The method of claim 3 wherein the parasiticide is selected from the group consisting of ivermectin, doramectin, avermectin, abamectin, and milbemycin.

5. The method of claim 4 wherein the parasiticide is ivermectin.

6. The method of claim 5 wherein the ivermectin is present in the liposome composition at a concentration of from about 0.01 percent to about 2.5 percent (weight/volume) .

7. The method of claim 6 wherein the ivermectin is present in the liposome composition at a concentration of from about 0.1 percent to about 2.0 percent (weight/volume) .

8. The method of claim 3 wherein the parasiticide is present in the drinking water at a concentration at least about 10 parts per million.

9. The method of claim 8 wherein the parasiticide is present in the drinking water at a concentration of from about 10 parts per million to about 1500 parts per million.

10. The method of claim 9 wherein the parasiticide is present in the drinking water at a concentration of from about 10 parts per million to about 500 parts per million.

11. The method of claim 3 wherein the vertebrate is a fowl .

12. The method of claim 3 wherein the vertebrate is a mammal .

13. The method of claim 12 wherein the mammal is selected from the group consisting of: bovines, equines, ovines, felines, porcines, caprines, and canines.

14. The method of claim 3 wherein the parasite is selected from the group consisting of roundworms, cecal worms , and mites .

15. The method of claim 3 wherein the parasite is selected from the group consisting of capillarial worms, lice, and ticks.

16. The method of claim 5 wherein the parasite is selected from the group consisting of roundworms, cecal worms, and mites.

17. The method of claim 5 wherein the parasite is selected from the group consisting of capillarial worms, lice, and ticks.

18. The method of claim 3 wherein the parasiticide is selected from the group consisting of doramectin, avermectin, abamectin, milbemycin, amprolium, bacitracin, chlortetracycline, erythromycin, lincomycin/spectinomycin, neomycin, oxytetracycline, piperazine, sarafloxacin, spectinomycin, sulfachloro-pyrazine, sulfadimethoxine, sulfamethazine, sulfaquinoxaline, tetracycline, and tylosin.

19. The method of claim 18 wherein the parasiticide is a compound selected from the group consisting of bacitracin, chlortetracycline, erythromycin, lincomycin, oxytetracycline, piperazine, spectinomycin, and tetracycline.

20. The method of claim 3 wherein the parasiticide is a salt of a compound selected from the group consisting of doramectin, avermectin, abamectin, milbemycin, amprolium, bacitracin, chlortetracycline, erythromycin, lincomycin/spectinomycin, neomycin, oxytetracycline, piperazine, sarafloxacin, spectinomycin, sulfachloro- pyrazine, sulfadimethoxine, sulfamethazine, sulfaquinoxaline, tetracycline, and tylosin.

21. The method of claim 20 wherein the parasiticide is a salt of a compound selected from the group consisting of bacitracin, chlortetracycline, erythromycin, lincomycin, oxytetracycline, piperazine, spectinomycin, and tetracycline.

22. The method of claim 1 wherein the pharmacologically active compound is a nutrient or growth regulator.

23. The method of claim 22 wherein the nutrient is a vitamin.

24. The method of claim 23 wherein the vitamin is selected from the group consisting of Vitamin A, Vitamin E, Vitamin D, and Vitamin K.

25. The method of claim 22 wherein the growth regulator is a steroid.

26. The method of claim 25 wherein the steroid is estrogen or a derivative of estrogen.

27. The method of claim 26 wherein the derivative of estrogen is estradiol .

28. A method of stabilizing a water labile pharmacologically active compound in aqueous solutions, comprising: encapsulating the water labile pharmacologically active compound in a liposome to enhance its stability in aqueous solutions .

29. The method of claim 28 wherein the water labile pharmacologically active compound is ivermectin.

30. The method of claim 28, wherein the aqueous solution is water.

31. The method of claim 28 wherein the water labile pharmacologically active compound is selected from the group consisting of: doramectin, avermectin, abamectin, milbemycin, amprolium, bacitracin, chlortetracycline, erythromycin, lincomycin/spectinomycin, neomycin, oxytetracycline, piperazine, sarafloxacin, spectinomycin, sulfachloro-pyrazine, sulfadimethoxine, sulfamethazine, sulfaquinoxaline, tetracycline, and tylosin, and any salt of any of these.

32. The method of claim 31 wherein the water labile pharmacologically active compound is selected from the group consisting of: bacitracin, chlortetracycline, erythromycin, lincomycin, oxytetracycline, piperazine, spectinomycin, and tetracycline and any salt of any of these.

33. The method of claim 28 wherein the pharmacologically active compound is a nutrient or growth regulator.

34. The method of claim 33 wherein the nutrient is a vitamin.

35. The method of claim 34 wherein the vitamin is selected from the group consisting of: Vitamin A, Vitamin E, Vitamin D, and Vitamin K.

36. The method of claim 33 wherein the growth regulator is a steroid.

37. The method of claim 36 wherein the steroid is estrogen or a derivative of estrogen.

38. The method of claim 37 wherein the derivative of estrogen is estradiol.

39. A method of increasing the solubility of a water insoluble pharmacologically active compound in aqueous solutions, comprising: encapsulating the water insoluble pharmacologically active compound in a liposome to enhance its solubility in aqueous solutions.

40. The method of claim 39 wherein the water insoluble pharmacologically active compound is ivermectin.

41. The method of claim 39, wherein the aqueous solution is water.

42. The method of claim 39 wherein the water insoluble pharmacologically active compound is selected from the group consisting of: doramectin, avermectin, abamectin, milbemycin, amprolium, bacitracin, chlortetracycline, erythromycin, lincomycin/spectinomycin, neomycin, oxytetracycline, piperazine, sarafloxacin, spectinomycin, sulfachloro-pyrazine, sulfadimethoxine, sulfamethazine, sulfaquinoxaline, tetracycline, and tylosin, and any salt of any of these .

43. The method of claim 42 wherein the water insoluble pharmacologically active compound is selected from the group consisting of: bacitracin, chlortetracycline, erythromycin, lincomycin, oxytetracycline, piperazine, spectinomycin, and tetracycline and any salt of any of these.

44. The method of claim 39 wherein the pharmacologically active compound is a nutrient or growth regulator.

45. The method of claim 44 wherein the nutrient is a vitamin.

46. The method of claim 45 wherein the vitamin is selected from the group consisting of: Vitamin A, Vitamin E, Vitamin D, and Vitamin K.

47. The method of claim 44 wherein the growth regulator is a steroid.

48. The method of claim 47 wherein the steroid is estrogen or a derivative of estrogen.

49. The method of claim 48 wherein the derivative of estrogen is estradiol.