VETERINARY PREPARATIONS FOR RUMINANT ANIMALS

Abstract: This invention provides veterinary preparations capable of being retained in the rumen of ruminants and providing the slow release of medicament within the rumen, said retention and release obviating the necessity of repeat dosing. The preparations each comprise a slow-release formulation (1) consisting of a veterinary medicament (1) in a solid or semi-solid matrix, the formulation (1) being enclosed in a plastics envelope (2) which is permeable (3) to rumen fluids, capable of constraint to allow per os administration and capable of being retained in the rumen by movement from this constraint. Suitable medicaments (1) include feed supplements, systemic insecticides, detergents, antibiotics and antiparasitics, and growth promotants.

Description: Veterinary Preparations for Ruminant Animals This invention relates to veterinary preparations for ruminant animals. Ruminant animals, particularly cattle and sheep, form an important group of animals which require periodic administration of veterinary medicines for the treatment and alleviation of various-conditions. For example, it is often desirable to treat such animals, either therapeutically or prophylactically, with mineral or vitamin supplements, antibiotics, systemic insecticides, detergents for the relief of cattle bloat, and/or anthelmintics or other anti-parasitic agents. The repeated administration of such veterinary medicines to animals at frequent time intervals is expensive and inconvenient. There is therefore much need for a dosing system to be devised which would effeciently supply the veterinary medicine during prolonged periods of time after administration of a single preparation. British Patent No: 1318259 describes a number of devices for retaining slow release veterinary medicament formulations in the rumen over an extended period of time, thereby achieving the desired result. This prolonged retention in the rumen is obtained by the devices having a relatively narrow first configuration which allows the devices to be administered per os to the ruminant, and a relatively broad second configuration which the devices assume or are caused to assume in the rumen thereby hindering or preventing their passage out of the rumen. A typical example of such a device specifically described in the Patent is a plastic cylindrical capsule containing a detergent for the control of bloat in cattle. The capsule is 150 mm long and 30 mm wide (thereby allowing per os administration), and consists of two half-cylinders hinged along one edge. The hinges are made from rubber and are biased so that the two halfcylinders spring apart in the rumen and thus become too wide to pass out through the rumen or to be regurgitated through the oesophagus. Each half-cylinder contains a gel of ethyl cellulose containing the desired anti-bloat agent which is leached from the gel by the rumen fluids over an extended period of time. The hinges are constructed so that under the rumen conditions they pull away from the half-cylinders after effective release of the agent thereby facilitating regurgitation of the fragmented device. We have now discovered a veterinary preparation which also achieves the desired result and has the advantage of being simple, cheap and easily manufactured. In this preparation the formulation is contained in a plastics envelope which is capable of being constrained around the formulation to allow per os administration of the preparation, and in the rumen of unfolding from its constrained administration position to effectively block any passage of the preparation out of the rumen. It should be noted that such a preparation is in no way described or suggested by the said Patent, which is in the mean concerned with more complex devices. Accordingly the present invention provides a veterinary preparation for ruminant animals, which preparation comprises a veterinary medicament contained in a solid or semi-solid matrix serving as a slow release formulation for the medicament, and a plastics envelope enclosing the formulation, which envelope is permeable to rumen fluids, is capable of being constrained in a position which allows per os administration of the preparation and is, in the rumen, capable of moving relative to this position to retain the preparation therein. Preferably, the envelope is in the form of an apertured bag, suitably constructed of plastics netting material. The formulation is suitably held loosely inside the envelope. The plastics envelope must be sufficiently flexible to be capable of being constrained for administration, and sufficiently resilient to unfold from this constrained position at least to an extent sufficient to effectively block passage of the preparation from the rumen. The envelope must also of course be non-toxic, and be stable to the rumen environment at least for the period of time during which release of the medicament contained therein is desired or possible. Thus examples of suitable materials from which the envelope may be made include semi-synthetic and synthetic plastics materials such as cellulose acetate, polyvinyl chloride, nylon, polyethylene, ethylene vinyl acetate copolymer and polyurethane, and synthetic rubbers such as silicone rubber polymers. Preferred materials include polyethylene. preC-erred e;bMinsts of the invention will now be described by reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a veterinary preparation according to the invention; and Fig. 2 is a perspective view of the preparation of Fig. 1 in its administration form. Fig. 3 is a perspective view of an alternative veterinary preparation. Referring to Figure 1, the slow release veterinary medicament formulation is shown in the form of cylindrical tablet 1 which is contained in a rectangular polyethylene envelope 2. The tablet 1 is shaped so that it fits neatly into one of the narrow ends of the envelope 2. The envelope is sealed at its edges, and is provided with a number of small holes 3 to render it permeable to rumen fluids so that, when the preparation is in the rumen,the tablet 1 is exposed to the rumen fluids and the medicament is leached therefrom at the desired slow rate. For administration, the envelope 2 is folded around the tablet to that the preparation assumes an approximately cylindrical administration form 4, as shown in Fig. 2. The envelope is constrained temporarily in this position around the tablet 1 by a thin strip of paper 5 gummed with a water soluble adhesive affixed around its circumference. This strip of paper 5 is readily removed by the rumen fluids after administration of the preparation in its administration form 4, and the envelope 2 then unfolds due to its inherent resilience and in this way attains an effective cross-sectional area great enough to retain the preparation in the rumen. The unfolding of the envelope 2 from its constrained position is of course assisted by the natural movement of the rumen environment. In this unfolded form in the rumen, the tablet 1 enclosed within the envelope 2 is exposed to the rumen fluids through the holes 3 thereby allowing the medicament to be leached therefrom. The size of the envelope 2 for administration to cattle is about 20 cm. in length and about 15 cm. in width, and for administration to sheep about 10 cm. in length and about 7 cm. in width. The cylindrical administration form of the preparation is about 5.5 cm. in length and 2.5 cm. in width for administration to cattle and about 5.0 cm. in length and 2.0 cm. in width for administration to sheep. This ensures easy and safe administration thereto. The polythene thickness is 0.1 mm, but a polythene thickness in the range 0.1 to 1mm. is preferably acceptable as this gives the required strength whilst retaining the flexibility necessary to allow the envelope to be constrained for administration as described. The envelope described in the above embodiment is in effect a single container for the formulation, which formulation is free to move within the envelope when the envelope unfolds in the rumen. This envelope design has the advantage of simplicity, as the preparation may be formed simply by placing the formulation in a pre-formed open envelope and sealing its edges. A second formulation may also readily be incorporated in such an envelope. Other envelopes within the scope of the present invention include envelopes wherein the formulation is held within one part of the envelope by means of an additional seal or seals, envelopes in which two or more formulations are held separate from each other by a seal or seals, and envelopes wherein part of the envelope contains the formulation and the rest ofthe envelope is in the form of a flap or wing. The envelope must be capable of being constrained in a position that allows per os administration of the preparation. It must also be capable of moving relative to this position once in the rumen to retain the preparation in the rumen. Thus normally the envelope will have a largest diameter in the range 4 to 30 cm., preferably 15 to 20 cm. for cattle, and in the range 2 to 20 cm., preferably 7 to 12 cm. for sheep. Suitably it is arranged into its administration position simply by folding it around the formulation enclosed therein. In order for the preparation to be administered safely and easily to the ruminant animal, the administration form of the preparation must be of a size and shape that is easily swallowed. Obviously this size and shape will vary with the ruminant being dosed, but for example we found that for cattle a preparation in an approximately cylindrical shape of length abour 4-6 cm. and diameter abour 2-3 cm. is particularly suitable. Preferably these dimensions are about 5 and 2.5 cm. respectively. Similarll for sheep, suitable cylindrical dimensions are length about 4-5 cm. and diameter about 1-2 cm., preferably 4.5 cm. and 1.5 cm respectively. The weight of the preparation will again depend on the ruminant being treated, and also on the medicament being used and the period of time during which this is to be made available within the rumen. Normally for cattle the weight is from about 10 to 200g, and for sheep from about 2 to 40g. In order for the slow release formulation enclosed within the envelopes to be exposed to the rumen fluids when the envelope unfolds in the rumen the envelope must be permeable to these fluids. This requirement may readily be achived by punching several small holes in the envelope as shown in Fig. 1. It has been found that if these holes are punched in a regular fashion in the enveloy then there is a risk that lines formed by adjacent holes may act as points of weakness causing premature rupture of the envelope in the rumen with consequent loss of the formulation. As it is obviously essential that the envelope retains the formulation within its confines at least until the majority of medicament held in the formulation has been slowly leached therefrom, it is preferred that these holes be punched in a random, manner in the envelope, as illustrated. Referring to Figure 3, the veterinary medicament formulation is in the form of a sheet 10 which is contained in a plastics netting envelope 11. The sheet is approximately 0.15 mm thick, 4 cm wide and 6 cm long, and the netting envelope is sealed along its edges by polyethylene strips 12 welded to the netting. The netting is suitably made from a low density polyethylene material "Netlon" (Registered Trade Mark) having regularly spaced holes about 3 mm x 3 mm in size. The device of Figure 3 can be rolled up into a similar configuration as shown in Figure 2 for administration per os to the sheep, and it will unroll to its planar configuration in the rumen. For administration to the ruminant, the envelope is constrained in a position which will allow passage of the preparation down the animal's throat into its rumen. While this constraint may be applied to the envelope by the throat of the animal itself, it is normally pref erred that some constraining means be associated with the envelope to hold it in this position for administration purposes. The constraining means is chosen so that it is quickly removed in the rumen environment to allow the envelope to unfold once it is in the rumen in the manner of the invention. This constraining means may be any device that is able to hold the envelope in its constrained position for administration, but is readily dissolved, destroyed, ruptured or otherwise removed by the rumen environment. Examples of suitable constraining means include gelatin string, gelatin tape, paper strips backed by water soluble adhesives, and water soluble paper. The active medicament used in the slow release formulation may be one more mineral supplements, e.g. a cobalt or magnesium salt; vitamin supplements, especially those of the vitamin B class; systemic insecticides, e.g. Diazinon or Dichlorvos; detergents for the relief of cattle bloat; antibiotics, such as ampicillin, amoxycillin, cloxacillin, flucloxacillin and the like; and/or anthel mintics or other anti-parasitic compounds such as parbendazole, rafoxanide, or diamphenethide (Corriban) or thiabendazole, tetramisole, levamisole, morantel, pyrantel or oxybendazole for nemato#es. Additional anthelmintics include fenbendazole, oxfendazole, albendazole, and avermectins, dihydroavermectins or combinations of these such as Ivermectin. The invention is particularly applicable to the provision of anthelmintics for gastro-intestinal nematodes and/or for use with anti-trypanosomiasis or anti-schistosomiasis compounds. It is also suitable for the administration of animal growth promotants. The medicament is contained in a slow release formulation. Many such formulations which cause delay in the release of the active principle from the formulation have been described. For example, the active ingredient may merely be mixed with an inert diluent,and the mixture compounded so that release of the active ingredient from the matrix is regulated by the mechanical disintegration or slow dissolution of the formulation. For this purpose the active ingredient may be compounded with kaolin, calcium sulphate, chalk, carboxymethyl cellulose, ethyl cellulose, methyl cellulose, dextran starch, gelatine, dimethyl siloxane resins and the like. More sophisticated slow release formulations may also be utilised. For instance the active ingredient may be incorporated, by coacervation or precipitation techniques, in a polymer matrix or shell, from which it may be leached by the rumen fluids over an extended period of time. The slow release formulation will be chosen so that the medicament contained therein is released in the rumen at the desired rate over the desired period of time. The present invention also provides a method of administering a veterinary medicament to a ruminant over an extended period of time, which method comprises causing the animal to swallow a veterinary medicament according to the invention. The constrained preparation may conveniently be administered using a conventional dosing gun.

Claims: CLAIMS: 1. A veterinary preparation for ruminant animals, comprising a veterinary medicament contained in a solid or semi solid matrix serving as a slow release formulation for the medicament, and a carrier for the medicament which is capable of being constrained in a position which allows per os administration of the preparation and is, in the rumen, capable of moving relative to this position to retain the preparation therein, characterised in that the carrier comprises a plastics envelope 2 enclosing the formulation 1, the envelope 2 being permeable to rumen fluids. 2. A veterinary preparation according to claim 1, characterised in that the envelope 2 is in the form of an apertured bag. 3. A veterinary preparation according to claim 1 or claim 2, characterised in that the envelope 2 is constructed of a synthetic polymer material. 4. A veterinary preparation according to anyone of the preceding claims characterised in that the envelope is constrained by means of a constraining element which retains the envelope in a folded configuration and is removable by rumen fluids after administration. 5. A veterinary preparation according to claim 4 characterised in that the constraining element comprises gelatin or paper tape, strip, or string. 6. A veterinary preparation according to any one of the preceding claims, characterised in that the formulation is in sheet form. 7. A veterinary preparation according to any one of the preceding claims, characterised in that the medicament comprises an anthelmintic. 8. A veterinary preparation according to any one of claims 1 to 6, characterised in that the medicament comprises an animal growth promotant. 9. A veterinary preparation according to any one of claims 1 to 6, characterised in that the medicament comprises a mineral additive or trace element additive. lo. A veterinary preparation according to any one of the preceding claims characterised in that the matrix comprises an inert diluent which slowly disintegrates or dissolves in the rumen to release the medicament.

Inventors: BREWER, MALCOLM DAVID, LEIPER, JOHN WILLIAM GUTHRIE
Applicants: BEECHAM GROUP PLC
Application year: 1980
Main classification: A61D7
IPC codes: A61D7, A61K9, A61P43, A61M31