Formulation for providing an enteric coating material

Abstract

The present invention relates to an enteric coating formulation, as well as methods for preparing and using said enteric coating formulation. In particular, the invention relates to an enteric coating formulation that is made up of foodeous approved materials.

Claims

1. An enteric coating formulation comprising an aqueous solution of a shellac salt and sodium alginate.

2. An enteric coating formulation as in claim 1, wherein the shellac is in aqueous form.

3. An enteric coating formulation as in claim 1, wherein the formulation is edible.

4. An enteric coating formulation as in claim 1, wherein the formulation comprises between 10-90% by weight shellac.

5. An enteric coating formulation as in claim 1, wherein the formulation comprises between 10-90% by weight alginate.

6. An enteric coating formulation as in claim 1, where there are equal quantities by weight of shellac and sodium alginate present in the formulation.

7. An enteric coating formulation as in claim 1, wherein the formulation is in the form of a spray solution or a suspension.

8. An enteric coating formulation as in claim 1, wherein the alginate is of a low viscosity grade.

9. An enteric coating formulation as in claim 1, wherein the alginate has a viscosity of between 200 and 300 cps.

10. An enteric coating formulation as in claim 1, wherein the formulation further comprises a plasticizer.

11. A method of applying an enteric coating formulation of claim 1, wherein the formulation is applied to a dosage unit by spraying.

12. A dosage unit comprising an enteric outer coating, wherein the enteric outer coating is of a formulation as in claim 1.

13. A method for preparing an enteric coating formulation as in claim 1, comprising the step of mixing an aqueous solution of an alkali salt of shellac with an aqueous solution of sodium alginate.

14. An enteric coating formulation comprising an aqueous solution of a shellac salt and an aqueous, low viscosity grade solution of sodium alginate.

15. An enteric coating formulation as in claim 14, wherein the sodium alginate solution has a viscosity of between 200 and 300 cps.

Description

(1) According to a first aspect of the present invention there is provided an enteric coating formulation comprising shellac and alginate.

(2) Preferably the alginate is sodium alginate.

(3) Preferably the Shellac is in aqueous form.

(4) Most preferably, the Shellac is in aqueous salt form.

(5) Preferably the formulation is edible.

(6) Most preferably the formulation comprises materials that are approved for food use.

(7) Optionally, the formulation comprises between 10-90% Shellac.

(8) Optionally, the formulation comprises between 10-90% alginate.

(9) Preferably, the formulation comprises equal quantities of Shellac and alginate.

(10) Preferably, the formulation is in the form of a spray solution or a suspension.

(11) Preferably, a low viscosity grade of alginate is used.

(12) Preferably, the alginate has a viscosity of between 200 and 300 cps.

(13) Optionally, a plasticiser may be added to the formulation.

(14) According to a second aspect of the present invention there is provided a method of applying an enteric coating formulation of the type described in the first aspect wherein the formulation is applied to a dosage unit as a spray.

(15) Optionally, the pH of the formulation may be adjusted to maintain a useable solution/suspension.

(16) Optionally, the pH of any of the components of the formulation may be adjusted to maintain a useable solution/suspension.

(17) According to a third aspect of the present invention there is provided a dosage unit comprising enteric outer coating which is itself comprises Shellac and alginate.

(18) Preferably the alginate is sodium alginate.

(19) According to a fourth aspect of the present invention there is provided a method for preparing an enteric coating comprising the steps mixing an aqueous solution of an alkali salt of Shellac with an aqueous solution of sodium alginate.

(20) In order to provide a better understanding of the present invention the invention will be described by way of example only and with reference to the following drawing in which Figure 1 shows a cross section of a dosage unit comprising an enteric coating according to the present invention.

(21) Sodium alginate is GRAS listed and recognised as a food additive in Europe. It is used as a stabilising agent, suspending agent, tablet and capsule disintegrant, tablet binder and viscosity increasing agent. However, until now it has never been suggested as a constituent of an enteric coating material. It is described in the art as being insoluble below pH3 and slowly soluble in neutral or alkaline solution and forms aqueous solutions. Therefore it would not appear obvious to use sodium alginate as part of an enteric coating.

(22) Neither Shellac, in free acid or alkaline salt form, nor sodium alginate form films that are acid resistant (where an acid is 0.1 N HCl) and dissolve or disintegrate in neutral/mildly alkaline conditions (i.e. pH 6.8 buffer), i.e. neither performs the function of an enteric coat.

(23) In the preferred embodiment of the present invention, Shellac, in the aqueous salt form, and sodium alginate are be mixed together to provide a formulation which forms a film that resists acid but disintegrates in neutral/mildly alkaline conditions. This film has the properties of an enteric film and is entirely composed of food use acceptable materials. Therefore, it is usable by the food and neutraceutical industry to coat non-pharmaceutical (i.e. non-licensed) dosage units where an enteric coating may still be of great use.

(24) In alternative embodiments, alginic acid, other salts of alginic acid (alginates) or alginic acid derivatives such as potassium alginate could be used in place of sodium alginate.

(25) As a preliminary step Shellac may be formed into a solution of the alkali salt using standard techniques known in the art. An example of such a technique is to heat Shellac in water, with stirring, to 50-55 C. then, after dissolution of the Shellac and the addition of 10% solution of ammonium hydrogen carbonate, the mixture is heated to 60 C., with stirring for a further 30 minutes. On cooling, the Shellac remains in solution as the alkali salt.

(26) The coating formulation is formed by mixing an aqueous solution and of an alkali salt of Shellac with an aqueous solution of sodium alginate. The content of either material may vary from 10% of one to 90% and will still demonstrate enteric properties in the film formed. Most preferably the constituents are present in equal quantities. The pH of the mixture, or either component within the mixture, may be adjusted and selected to maintain a useable solution or suspension.

(27) The aqueous solution of the alkali Shellac salt may be formed from Shellac as part of the preliminary process using methods known in the art.

(28) It is also worth noting that sodium alginate is commercially available as different grades which form solutions of wildly different viscosities. Preferably, in this case, a low viscosity grade of sodium alginate will be used. The preferred viscosity of the sodium alginate is 200-300 cps (centipoise), defined as a viscosity of a 3% solution in water with a sequestering agent.

(29) A plasticiser may be added to the formulation to modify the flexibility of the film formed to suit the dosage requirements. Examples of plasticisers are triethylcitrate, polyethylene glycol, polypropylene glycol and glycerin monostearate. The plasticisers would typically be added in the 5-25% range. The aqueous Shellac/sodium alginate solution or suspension can, at suitable concentration which is spraying system dependent, be sprayed using commercial equipment by personnel skilled in the art to form films on dosage units.

(30) It can be seen that the present invention has a number of benefits over the prior art and up until now this combination of materials has not been known to produce a film that has enteric properties and is acceptable for food use. As none of the materials themselves perform in an enteric manner it is somewhat surprising to find that the combination of material produces a film that shows enteric properties, a property possessed by neither of the components.

(31) It should be noted that the embodiments disclosed above are merely exemplary of the invention which may be embodied in many different forms. Therefore, details disclosed herein are not to be interpreted as limiting but merely as a basis for claims and for teaching one skills in the art as to the various uses of the present invention in any appropriate manner.