WO2010052727A1

WO2010052727A1 - High performance film coating compositions

Info

Publication number: WO2010052727A1
Application number: PCT/IN2009/000018
Authority: WO
Inventors: Suresh Rukmanand Pareek; Chetan Rajsharad
Original assignee: Ideal Cures Private Limited
Priority date: 2008-11-04
Filing date: 2009-01-06
Publication date: 2010-05-14

Abstract

Disclosed herein is dry film coating compositions comprising of a mixture of low viscosity hydroxy propyl methyl cellulose and modified starch as the essential component along with other water soluble polymers, diluents, plasticizers, excipients like suspending agents, pigments, lubricants, glidents, opacifiers, colours, flavours, sweeteners etc. for use in coating of pharmaceutical tablets, nutritional supplements, food products, confectionery, agricultural seeds and the like. The invention further discloses method for manufacturing such compositions and a method for coating a substrate using the invented coating compositions.

Description

HIGH PERFORMANCE FDLM COATING COMPOSITIONS

Technical field :

This invention relates to the field of film coating compositions for substrates like pharmaceutical tablets, nutritional supplements, food products, confectionery, agricultural seeds for providing protection to the substrate from environmental conditions like light, humidity, atmospheric gases etc. wherein the solids content in the coating suspension can be raised upto 30% w/w so as to complete the coating very quickly.

Background of the Invention ;

Gone are the days when tablet coating was referred to as an "Art". The science of tablet coating has come a long way during last couple of decades that today the formulation scientist has a range of film coating formulation / materials to choose from for any specific coating application. Though lots of polymers have been tried and are available for film coating, cellulosic polymers (HPMC, Methyl cellulose, Ethyl cellulose etc.) are still by and large the first choice due to their inert nature and solubility in wide range of solvents (aqueous as well as non-aqueous). A large number of publications are available in which the film coating with such cellulosic polymers has been demonstrated.

Yet another polymer, polyvinyl alcohol (PVA) which is now increasingly being used for film coating due to its adhesive properties and high water solubility, however, this polymer is not very suitable for non-aqueous coating applications as it is not soluble in organic solvents (though the science is moving toward total aqueous coating, still lots of products all over the world are coated with solvent based or hydro-alcoholic based coating due to moisture sensitivity of some of the active ingredients). Most of the other polymers are not so popular among the formulation scientist unless otherwise for any specific application.

In most of the cases, where organic solvents have been used as the solvent, the solids content in the coating suspension has been 3 - 6% w/w as it has been found difficult to add large amount of solids into the coating suspension due to the high volatility of organic solvents which then leads to spray drying and rough surface finish. Some scientist have tried to replace part of the organic solvent with water and make a hydro-alcoholic solvent system, thereby reducing the volatility of the solvent but in such cases also the solid content can not be raised beyond 10% w/w as the suspension viscosity goes beyond usable limits. In case water being the solvent, formulators have been able to add upto about 12% w/w solids in HPMC based film coating formulations.

US patent 5,630,871 describes a film coating composition wherein HPMC has been combined with lactose thereby increasing the solids content in the water based coating suspension to about 17% w/w. Increasing the solids content beyond this level, increases the suspension viscosity so high that it becomes unsuitable for coating application,. Further drawback of this composition is as it is applicable only with water as the solvent and the same is not been able to use with any organic solvent or hydro-alcoholic solvent system.

US patent 5,885,671 describe film coating compositions based on polyvinyl alcohol as the polymer wherein the solid content in the film coating composition can be as high as 20% w/w, however, due to the sticky nature of PVA, the coating process using these compositions is comparatively slow and require fairly high tablet temperature to prevent tablet to tablet sticking (desired tablet temperature for these compositions is 42 - 45 deg.C as compared to 38 - 40 deg.C for HPMC based coating compositions), thus, requiring high energy consumption for the operation. It has been observed that though the solid content of composition described in US patent 5,630,871 is only 15 - 17% (as compared to 20% for PVA based compositions), the coating process is much easier and faster with the composition of 5,630,871.

Objective of the Invention :

Therefore, the objective of this invention is to develop a film coating formulation wherein the solid content in the coating composition can be raised to much higher levels as compared to currently available coating compositions so as to reduce the coating time and overall energy consumption. Another objective of the invention is to provide a composition with reasonable viscosity, and good film adhesion properties so as to have excellent logo definition on the finish product and also easy to work with all kind of available coating machines.

Further, objective of the invention is to provide a method for coating the substrate using the compositions of the invention.

Summary of the Invention :

In accordance with the above objectives, the present invention provides cost - effective dry film coating compositions comprising of HPMC and Modified Starch as the essential ingredients along with other commonly used polymers, plasticizers, excipients like suspending agents, pigments, diluents, lubricants, glidents, opacifiers, flavours, sweeteners etc. for use in coating of pharmaceutical tablets, nutritional supplements, food products, confectionery, agricultural seeds and the like.

In another aspect, the invention provides a method of coating a substrate using the invented coating compositions.

Detailed Description :

The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated.

It is well known in the art of film coating that HPMC is a very versatile polymer which is soluble in aqueous as well as non-aqueous solvents and hence more popular among the scientific community. The two most important grades (based on viscosity) of HPMC which are commonly used in film coating compositions are 5 cps (Methocel E-5, Pharmacoat 606 and other brands) and 15 cps (Methocel E- 15, Pharmacoat 616 and other brands). It is well known that 15 cps grade is generally used for non-aqueous coating (solid content in coating suspension being 3 - 6% w/w) whereas 5 cps grade is used for aqueous coating (solid content in coating suspension being 8 - 11% w/w). There is yet another grade of low viscosity of HPMC i.e. 3 cps which is also easily available but is not very popular among the formulators as the film strength of this polymer is very low and is generally found to be not suitable for film coating compositions. US patent 5,630,871 has described the use of HPMC 15 cps in aqueous coating by combining it with lactose with the solid content in the coating composition being 15 - 17% w/w.

As the film coating process is an additional step for the manufacturing of pharmaceutical tablets, any reduction in the coating process time will be the most desired development and this can be achieved by increasing the solid content in the coating suspension so that one has to spray less amount of suspension thereby reducing the coating time and energy consumption.

Thus, according to preferred embodiment, a dry film coating composition for use in pharmaceutical tablets, nutritional supplements, food products, confectionery or agricultural seed comprising : a) a low viscosity cellulosic polymer; b) modified starch; and c) optionally in combination with other water soluble polymer, diluents, glidents, plasticizer and pigments.

The cellulosic polymer is selected from low viscosity grade of hydroxyl propyl methyl cellulose selected among 3cps, 5cps, 15cps or 50cps, hydroxyl propyl cellulose or methyl cellulose used either alone or in combination thereof. The cellulosic polymer is advantageously present in a range of about 5% to about 50%; more preferably in a range of about 10% to about 45% by weight of the dry composition.

The modified starch is present in a range of about 3% to about 25%; more preferably in a range of about 5% to about 20% by weight of the dry composition.

The coating composition optionally comprise water soluble polymer such as polyvinyl alcohol, sodium CMC, alginic acid, sodium alginate, guar gum, gum acacia, gellan gum, xanthan gum either alone or in combination thereof. The water soluble polymer is polyvinyl alcohol used in an amount of about 0% to about 25%; more preferably in a range of about 0% to about 18% by weight of dry composition. The coating composition of the present invention further comprises a diluent such as lactose, mannitol, sucrose, dextrose, maltodextrin, microcrystalline cellulose either alone or in combination thereof, present in a range of about 0% to about 15%; more preferably in a range of about 0% to about 10% by weight of the dry composition.

Glidant used in the coating composition is selected among talc, fumed silica, magnesium stearate, stearic acid, kaolin, magnesium trisilicate either alone or in combination thereof. One preferred glidant is talc being present in a range of about 0% to about 25%, more preferably in a range of about 0% to about 15% by weight of the dry composition.

Polyethylene glycol, propylene glycol, triacetin, liquid paraffin, diethyl phthalate, dibutyl phthalate, glycerin, lecithin, triethyl citrate, fractionated coconut oil, castor oil or polysorbate-80 were used as plasticizers either alone or in combination thereof.

The coating composition of the invention comprise polyethylene glycol as plasticizer in an amount ranges about 0% to about 25%; preferably in a range of about 0% to about 20% by weight of the dry composition.

The coating composition further includes pigment / opacifier / colouring agent selected from titanium dioxide, calcium carbonate, calcium phosphate, iron oxide colours, lake colours, soluble colours, mica based pearlescent pigments, natural colours used either alone or in combination thereof.

The pigment / opacifier / colouring agent is present in a range of about 0% to about 35% by weight of the composition.

The coating composition further includes a sweetener selected from sodium saccharin, aspartame, neutrame either alone or in combination thereof being present in a range of about 0% to about 7%; more preferably in a range of about 0% to about 3% by weight of the composition. The coating composition further includes a flavouring agent in a range of about 0% to about 10% by weight of the dry composition.

In another preferred embodiment, the invention provides a method for manufacturing the coating composition which method comprises dry blending the ingredients of the composition in a suitable mixer and then sieving through a suitable screen to ensure homogenous mixing.

Alternately, the method comprises dry blending the ingredients of composition in a mixer; granulating the blend with water or other suitable binder solution; drying the granules, and sieving through suitable screen.

Another alternative method comprises dry blending the ingredients of composition in a mixer; converting the blend to paste form or liquid form by mixing enough solvent, and sieving the paste / liquid through suitable screen to ensure homogeneity.

Compositions with 20% solid content:

The present inventors have found that the use of Modified Starch (USP grade) is a very useful excipient in the film coating compositions. Certain combinations of modified starch with HPMC (3 cps, 5 cps and 15 cps) were worked out and it was found that a combination of modified starch with 3 cps grade of HPMC offers great opportunities in film coating. Though, the film strength of this combination was quite reasonable, it was found that the film strength can further be increased by replacing a small part of HPMC 3 cps with HPMC 15 cps without compromising much on the suspension viscosity so that the solid content of the suspension can easily be raised upto 20% w/w or more. This is the first time a HPMC based film coating composition could be made possible with 20% or more solid content with easily workable suspension viscosity (200 - 300 cps) and fairly good film strength. The inventors further found that addition of small amount of an excipient like lactose further enhances the film properties in terms of film smoothness and sheen. Thus, a combination of HPMC 3 cps, HPMC 15 cps, modified starch and lactose provides a film coating composition which provides very fast coating process (laboratory scale operation upto 500gm tablets lot in a conventional coating pan set-up could be easily completed in about 20 minutes time with 2.5% coating weight gain) with excellent logo definition, surface smoothness, surface coverage, colour uniformity and ease of operation. Coating trials in more efficient coating machines like perforated pan set-up, also produced excellent results as compared to earlier known compositions.

Yet another advantage which was observed in the above described composition is that the colour uniformity was excellent. It has been observed that in composition of US patent 5,630,871 (HPMC and lactose based with 15 - 17% solid content) the uniformity of dark colours (using high concentration of pigments) is very difficult, it generally ends up with frost effect giving small white specs against very dark colour shade. Any such disadvantage was not observed in the newly invented composition. The invented composition works well with aqueous or hydro-alcoholic or organic solvent systems, the solids content in the coating suspension can be around 20% w/w whereas for organic solvent system the solid content has to be reduced according to the volatility of the solvents used.

Compositions with 30% solid content:

The combination of HPMC and Modified Starch offered yet another opportunity during further experimentations, and the coating compositions with solid content upto 30% w/w could be prepared by replacing part of HPMC by PVA with workable suspension viscosity, reasonable film strength, excellent film adhesion, surface coverage, colour uniformity, logo definition and ease of operation. The sticky nature of PVA could be easily overcome in such composition still gaining the advantage of film forming properties of PVA. Thus, in the invented composition, the goodness of both polymers HPMC and PVA were obtained and the disadvantages with these polymers were reduced to the minimum extent, thereby increasing the efficiency of film coating operation to the fullest possible level. The laboratory scale operation in conventional pan set-up (500gm tablet lot) could easily be completed in about 15 minutes time with excellent results.

Accordingly, dry film coating composition of the present invention suitable for use in coating pharmaceutical tablets, nutritional supplements, foods, confectionary and agricultural seeds were prepared which comprises HPMC and Modified Starch, optionally in combination with PVA, Lactose, a plasticizer system, opacifier and pigments. The invented composition has excellent film forming ability and film adhesion to the substrate and provides excellent protection to the substrate against environmental conditions. The invented composition can easily be used with water or combination of water and alcohol (for moisture sensitive actives) as the solvent system. The invention also provides ample opportunity to make variations in preparing compositions suitable for any specific application by varying the concentration of different ingredients, solvent system and the solid content of the coating suspension.

Advantageously, in a typical embodiment, the dry film coating composition of the present invention may comprise of HPMC 3cps 15-50% w/w and Modified Starch 3-25%, in addition to these it may also contain HPMC 15cps 2-15% w/w or PVA 3-25%. Among the other excipients which may be added to the composition comprises 2- 15% w/w of a diluent chosen from lactose, mannitol, sucrose, dextrose, maltodextrin, a plasticizer system 5-25% w/w, pigments / opacifiers 0-30% w/w, Talc 0-25% w/w. Other excipients which may optionally be added to the composition to achieve certain specific applications like flavours and sweeteners. Some of the additives like HPMC 5cps, HPMC 6cps, HPMC 50cps, HPC, HEC, methyl cellulose, sodium CMC, aqueous dispersion of ethyl cellulose, gellan gum, xanthan gum, sodium alginate, alginic acid, calcium phosphate, calcium carbonate, microcrystalline cellulose, fumed silica, kaolin, magnesium stearate, stearic acid, magnesium trisilicate, either alone or in combination of more than one ingredient may be added to the invented composition to make alternate compositions.

The invented composition can very easily be manufactured by dry mixing of various ingredients (mixing may need specific order of addition depending on the ingredients used), carrying out the colour matching exercise using spectrophotometric colour scan method.

As described above, the invented composition can also be easily granulated before marketing in order to avoid the dust generation while handling the product at the user site. The granulation can be carried out either for the whole composition or a part of the composition and then mixing with other ingredients. The invented composition may also be converted to either to the paste form or to the liquid form by mixing with suitable solvent system before marketing and then diluting the same further at the user site, thereby eliminating any possibility of powder dust.

In another preferred embodiment, the invention describes a method for coating substrates. Accordingly, a method for coating substrates such as pharmaceutical tablets, nutritional supplements, food, confectionery, agricultural seeds, and the like, with a film coating composition comprising of the steps of:

a) mixing the coating composition with water to form a smooth dispersion (the solid content in the dispersion can be varied 20-30% w/w according to ingredients used); b) applying an effective amount of said coating dispersion onto said substrate to form a film on the said substrate (the coating weight gain can be varied from 2 - 2.5% w/w for normal film coating to 4 - 6% w/w for protective coating against environmental conditions), and c) drying the film coating on said substrate.

In accordance with the above method, the dry mix composition can easily be converted into coating suspension by suspending in suitable solvent system (aqueous, non-aqueous or hydro-alcoholic). The suspension becomes ready for coating quite quickly when a propeller stirrer is used for suspension preparation.

The following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of examples and for the purpose of illustrative discussion of preferred embodiments of the invention.

The ranges of each component of the dry coating compositions of the invention are as follows, by weight : Example 1

General method of preparation of the coating composition and coating process :

The dry components of the formulation were blended together in a dry powder mill or a blender, for 20 minutes, until a homogeneous mixture achieved, resulting in the formulation of the inventive dry film coating composition. Optionally, the dry film coating composition of the invention may be granulated using a planetary mixer. After the dry film coating composition was loaded into the mixer, sufficient water was slowly added during the mixing process until the composition forms slightly adherent granules. These granules were then passed through 2 mm screen and then dried in an oven at 30⁰C until the moisture content below 4% is achieved. The composition was then sieved again to convert the whole mass to 20 mesh size to make it ready for use in a non-dusting granular form. Other methods of granulation, which may be used, are spray granulation and roller compaction.

30gm of the resulting film coating composition was dispersed into 70 gm of purified water to form an inventive coating dispersion (30% solids), and the dispersion was sprayed onto 500gm of tablets using a conventional coating pan set-up to form the inventive coating on the tablets. The tablets were rotated in the coater at a rotation speed of 30 rpm. Hot air at 60 ± 2⁰C, was used to evaporate the solvent in the coating dispersion and to maintain the tablets at around 38⁰C. The coating of around 2.2% weight build up was completed in 15 minutes.

Upon completion of the coating process, the tablets showed a smooth surface with excellent logo definition and colour uniformity.

The following examples 2 to 11, which show different formulations of the dry film coating composition of the invention, further illustrate the invention. In each example 2 to 11, the film coating composition was manufactured using the method of example 1.

Example 2 :

HPMC 3cps 32.00

Modified starch 14.00

HPMC 15cps 5.00

Lactose 6.00

PEG 400 7.00

PEG 6000 7.00

Talc 12.00

Titanium dioxide 10.00

Lake indieo carmine 7.00

Example 3:

HPMC 3cps 30.00

Modified starch 10.00

HMPC 15cps 8.00

Lactose 8.00

Propylene glycol 9.00

Talc 12.00

Titanium dioxide 15.00

Iron oxide yellow 8.00 Example 4 :

HPMC 3cps 38.00

Modified starch 9.00

HPMC 15cps 6.00

Triacetin 10.00

Talc 15.00

Titanium dioxide 13.00

Lake erythrosine 4.00

Iron oxide red 5.00

Example 5 :

HPMC 3cps 60.00

Modified starch 8.00

Lactose 8.00

PEG 6000 10.00

Talc 14.00

Example 6 :

HPMC 3cps 26.00

Modified starch 10.00

PVA 11.00

Lactose 4.00

PEG 400 7.00

PEG 6000 10.00

Talc 15.00

Titanium dioxide 7.00

Lake sunset yellow 10.00 Example 7 :

HPMC 3cps 28.00

Modified starch 8.00

PVA 12.00

Triacetin 7.00

PEG 4000 10.00

Talc 12.00

Candurin colour 23.00

Example 8 :

HPMC 3cps 35.00

Modified starch 6.00

PVA 8.00

PEG 400 6.00

PEG 8000 12.00

Candurin colour 33.00

Example 9 :

HPMC 30.00

Modified starch 12.00

PVA 11.00

PEG 400 6.00

PEG 6000 8.00

Talc 10.00

Chocolate flavour 8.00

Sodium saccharin 0.50

Titanium dioxide 7.50

Iron oxide red 7.00

Example 10 :

HPMC 3cps 32.00 Modified starch 12.00 HPMC 5cps 5.00 Triacetin 9.00

Polysorbate-80 1.00

Talc 12.00

Lemon flavour 9.00

Titanium dioxide 10.00

Tartrazine 2.00

Lake tartrazine 8.00

Example 11 : -

HPMC 30.00

Modified starch 10.00

PVA 11.00

Lecithin 4.00

PEG 6000 8.00

Talc 14.00

Aerosil-200 1.00

Titanium dioxide 17.00

Lake carmosine 5.00

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative examples and that the present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments and examples be considered in all respects as illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

We claim,

1) A dry film coating composition for use in pharmaceutical tablets, nutritional supplements, food products, confectionery or agricultural seed comprising : a) a low viscosity cellulosic polymer; b) modified starch; and c) optionally in combination with other water soluble polymer, diluents, glidents, plasticizer and pigments.

2) The coating composition as claimed in claim 1, wherein the cellulosic polymer being low viscosity grade of hydroxyl proply methyl cellulose selected from 3cps, 5cps, 15cps or 50cps, hydroxyl propyl cellulose, methyl cellulose used either alone or in combination thereof.

3) The coating composition as claimed in claim 1, wherein the cellulosic polymer is present in a range of about 5% to about 50%; more preferably in a range of about 10% to about 45% by weight of the dry composition.

4) The coating composition as claimed in claim 1, wherein the modified starch is present in a range of about 3% to about 25%; more preferably in a range of about 5% to about 20% by weight of the dry composition.

5) The coating composition as claimed in claim 1, wherein the said diluent being lactose, mannitol, sucrose, dextrose, maltodextrin, microcrystalline cellulose either alone or in combination thereof.

6) The coating composition as claimed in claim 5, wherein the said diluent is lactose being present in a range of about 0% to about 15%; more preferably in a range of about 0% to about 10% by weight of the dry composition.

7) The coating composition as claimed in claim 1, wherein the optional water soluble polymer being polyvinyl alcohol, sodium CMC, alginic acid, sodium alginate, guar gum, gum acacia, gellan gum, xanthan gum either alone or in combination thereof. 8) The coating composition as claimed in claim 7, wherein the said water soluble polymer is polyvinyl alcohol being present in a range of about 0% to about 25%; more preferably in a range of about 0% to about 18% by weight of dry composition.

9) The coating composition as claimed in claim 1, wherein the said glident being talc, fumed silica, magnesium stearate, stearic acid, kaolin, magnesium trisilicate either alone or in combination thereof.

10) The coating composition as claimed in claim 9, wherein the said glident is talc being present in a range of about 0% to about 25%, more preferably in a range of about 0% to about 15% by weight of the dry composition.

11) The coating composition as claimed in claim 1, wherein the plasticizer is selected form polyethylene glycol, propylene glycol, triacetin, liquid paraffin, diethyl phthalate, dibutyl phthalate, glycerin, lecithin, triethyl citrate, fractionated coconut oil, castor oil or polysorbate-80 used either alone or in combination thereof.

12) The coating composition as claimed in claim 11, wherein the said plasticizer is polyethylene glycol being present in a range of about 0% to about 25%; more preferably in a range of about 0% to about 20% by weight of the dry composition.

13) The coating composition as claimed in claim 1, further including pigment / opacifier / colouring agent selected from titanium dioxide, calcium carbonate, calcium phosphate, iron oxide colours, lake colours, soluble colours, mica based pearlescent pigments, natural colours used either alone or in combination thereof.

14) The coating composition as claimed in claim 13, wherein the said pigment / opacifier / colouring agent is present in a range of about 0% to about 35% by weight of the composition.

15) The coating composition as claimed in claim 1, further including a sweetener selected form sodium saccharin, aspartame, neutrame either alone or in combination thereof being present in a range of about 0% to about 7%; more preferably in a range of about 0% to about 3% by weight of the composition.

16) The coating composition as claimed in claim 1, further including a flavouring agent in a range of about 0% to about 10% by weight of the dry composition.

17) A method for manufacturing the coating composition of claim 1 comprising of steps of : a) dry blending the ingredients of composition of claim 1 in a suitable mixer and then sieving through a suitable screen to ensure homogenous mixing, or a) dry blending the ingredients of composition of claim 1 in a mixer; b) granulating the blend with water or other suitable binder solution; c) drying the granules; and d) sieving through suitable screen or a) dry blending the ingredients of composition of claim 1 in a mixer; b) converting the blend to paste form or liquid form by mixing enough solvent; and c) sieving the paste / liquid through suitable screen to ensure homogeneity.

18) A method for coating substrates such as pharmaceutical tablets, nutritional supplements, food products, confectionery, agricultural seeds, and the like, with a film coating composition of claim 1 comprising the steps of : a) mixing the coating composition of claim 1 into water or into organic solvents or into a combination of water and alcoholic solvents' to form a smooth dispersion; b) applying an effective amount of said coating dispersion onto said substrate in a suitable coating machine to form a film on the said substrate, and c) drying the film coating on said substrate.