This invention relates to a monolayer sugar-coated tablet which is coated with a sugar-coating liquid containing 30-54% by weight of saccharide, 2-10% by weight of polyethylene glycol and 0.2-2% by weight of polyvinylpyrrolidone, and a process for preparing the same. According to the invention, a monolayer sugar-coated tablet and a process for preparation thereof are provided with very great economical advantages that the skill required for conventional sugar-coating processing is unnecessary and furthermore consumption of sugar-coating material can be reduced and the processing time can be shortened.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to monolayer sugar-coated tablet which is coated with single sugar-coating liquid of specific composition and process for preparation thereof. Because the monolayer sugar-coated tablet of the invention is prepared in single step using a single sugar-coating liquid, it does not require the skill and high technical level of artisans which are normally demanded for ordinary sugar-coating processing. Furthermore, it allows reduction in consumption of sugar-coating material and reduction in processing time, and is economically very advantageous.

2. Description of the Prior Art

Sugar-coating has been widely practiced with pharmaceutical formulations not only for imparting regular shapes to sugar-coated tablets to improve the latter's appearance, but also for the purpose of increasing moisture-proof property to prevent deterioration of the coated product and facilitate administration. Whereas, conventional sugar-coating method requires plural steps including sub-coating, smoothing, coloring, finishing and polishing, and hence need many processing hours. Furthermore, skills are essential for the operations and because the composition of sugar-coating liquid used is normally different for each step, formulation and preservation of those liquids cost much labor. Comparing with methods for preparing other formulations, therefore, the method is considerably cost-taking.

Namely, in generally practiced preparation method of a sugar-coated tablet, first in the sub-coating step uncoated tablets are coated with a sugar-coating liquid whose chief components are saccharide, additives and binder, several tens of times to round the angular portions of the uncoated tablets; then coated with a sugar-coating liquid containing less amount of the additives and having an increased concentration of saccharide several times in the smoothing step, to smooth out the sub-coated layer surface. If necessary the tablets are then sent to a coloring step, wherein they are coated with a pigment-containing sugar-coating liquid several times to be colored, followed by a finishing step in which the surfaces of the tablets are given smoothness suitable for polishing. Finally wax or the like is scattered on the tablets in a polishing step to impart gloss to their surfaces and provide the finished sugar-coated tablet.

Preparation of sugar-coated tablet thus generally requiring complex, multi-step processing and considerably long processing time, attempts to simplify the sugar-coating steps and shorten the processing time have been reported in the past. For example, Laid-open (Kokai) Patent Application Sho 51(1976)-70808A-JP disclosed a sugar-coating method in which sub-coating and/or smoothing steps are dispensed with, by using a sugar-coating liquid obtained by addition of an inorganic high molecular weight substance chiefly of montmorillonite to aqueous solution of sucrose. Kokai Sho 56(1981)-87518A-JP disclosed a preparation process of thin-layer sugar-coated tablets which were spray-coated with about 9 to 40% to the weight of uncoated tablets of a sugar-coating liquid containing about 10-80% by weight of talc to the sugar as suspended in said liquid. Sho 56(1981)-39287B1-JP disclosed a process for making sugar film-coated tablets in which the uncoated tablets were directly coated with a film of a sugar-coating liquid containing at least 10% by weight of polyvinyl alcohol, not more than about 35% by weight of saccharide and an adequate amount of a tackiness-reducing agent. The sugar coatings obtained in those methods, however, are invariably thin, and the sugar-coated tablets obtained thereby cannot fully exhibit the properties characteristic of sugar-coated tablet. Kokai Hei 9(1997)-175997A-JP, furthermore, disclosed a method of coating with a sugar-coating liquid containing 1-4 parts by weight of hydroxypropylmethylcellulose having specific properties and 5-25 parts by weight of a filler formed chiefly of finely pulverized talc. Said process, however, allowed to carry out the sub-coating step and smoothing step using a sugar-coating liquid of identical composition, but the subsequent finishing step and polishing step could not be omitted. Hei 7(1995)-17497B1-JP disclosed a sugar-coating method comprising sprinkling a sugar-coating liquid which contained 40-65% by weight of saccharide and 0.04-1.6% by weight of a surfactant. However, because the sugar-coating liquid used in this method contained the surfactant at such a low ratio, the resulting sugar-coated tablet lacked sufficient smoothness and its gloss also was unsatisfactory.

SUMMARY OF THE INVENTION

The object of the invention is to provide monolayer sugar-coated tablet, and a process for preparation thereof, which are utilizable with high economical advantages because the process does not require skill and high technical level of artisans which are necessary for conventional sugar-coating processing and still enables to decrease consumption of sugar-coating materials and to shorten the processing time.

We have discovered that use of a sugar-coating liquid containing saccharide, polyethylene glycol and polyvinylpyrrolidone at specific ratios enables to carry out the sub-coating, smoothing, coloring and finishing steps without using sugar-coating liquids of different compositions and, furthermore, the polishing step can be dispensed with. We have also found, while it is normally difficult to prepare evenly colored sugar-coated tablet, that colored sugar-coated tablet with good even coloring can be very easily prepared.

Thus, according to the invention, monolayer sugar-coated tablet which is coated with a sugar-coating liquid containing 30-54% by weight of saccharide, 2-10% by weight of polyethylene glycol and 0.2-2% by weight of polyvinylpyrrolidone is provided.

DESCRIPTION OF SPECIFIC EMBODIMENTS

In the invention, examples of saccharide useful for the sugar-coating liquid include sucrose, glucose, lactose, sorbitol, mannitol and xylitol. Of those, sucrose is particularly preferred. Concentration of saccharide in the sugar-coating liquid to be used in the invention generally may range 30-54% by weight, preferably 35-45% by weight.

Polyethylene glycol is used for the purpose of increasing extendability of the sugar-coating liquid to uniformize thickness of the coating layer, and preventing deposition of the sugar-coating liquid to pans. Normally polyethylene glycol of average molecular weight ranging from about 1,500 to about 20,000, in particular, from about 7,300 to about 9,300, are conveniently used. The polyethylene glycol concentration in the sugar-coating liquid to be used in the invention may normally range 2-10% by weight, preferably 3-5% by weight.

Polyvinylpyrrolidone which is used as a binder in the sugar-coating liquid according to the invention has an average molecular weight within a range of from about 28,000 to about 1,500,000, in particular, from 1,00,000 to about 1,500,000. It is advantageous to use it at a concentration of 0.2-2% by weight, preferably 0.3-0.5% by weight, to the sugar-coating liquid.

The sugar-coating liquid may additionally contain, as necessity arises, additives which are routinely used for this kind of sugar-coating liquid, e.g., at least one of pigments, calcium carbonate, talc, titanium dioxide, calcium phosphate, calcium sulfate, silicon dioxide, gelatine, pullulan, gum arabic, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyvinyl alcohol, polypropylene glycol, polyoxyethylene-polyoxypropylene glycol and the like, in particular, calcium carbonate and talc. The total concentration of those additives is normally not higher than 40% by weight, preferably within a range of 15-30% by weight, of the sugar-coating liquid.

When colored sugar-coated tablet is desired, evenly colored sugar-coated tablet can be readily prepared by adding an adequate amount of desired pigment(s) to the sugar-coating liquid according to the invention and coating uncoated tablets therewith.

Normally in processing of colored sugar-coated tablet, a pigment-containing colored layer is provided between the smoothed layer and finished layer to prepare colored sugar-coated tablet. However, colored sugar-coated tablets prepared by such conventional process are apt to be not evenly colored due to insufficient thickness of the coloring layer among other reasons. Hence long accumulated experiences and high skill are required to produce evenly colored sugar-coated tablet. Whereas, when the sugar-coating liquid of the invention is used, evenly colored sugar-coated tablet can be prepared with great technical ease, simply by adding any desired pigment to the sugar-coating liquid. Thus the invention is used with particular advantage for making colored sugar-coated tablets.

In the sugar-coating liquid of the invention, the use ratio of the liquid medium, e.g., water, is not critical. Whereas, it can be generally used at a concentration in the order of 30-50% by weight, preferably in the order of 30-33% by weight, to the sugar-coating liquid.

The monolayer sugar-coated tablet of the invention can be produced by coating uncoated tablets with a sugar-coating liquid of the earlier described composition using a sugar-coating apparatus. As the sugar-coating apparatus useful in that occasion, any of those conventionally used in sugar-coating processing can be similarly used, for example, a pair-type or onion-type coating pan, an aerator type coating pan, and the like.

For example, when an onion-type coating pan of 30 cm in inner diameter is used, uncoated tablets are charged in the coating pan, and while rotating the pan at a rate of about 30-45 rpm, a sugar-coating liquid in an amount of about 0.5-4% by weight to the uncoated tablets per application is poured onto the tablets mannually or sprayed with a spray gun, and then air of about 30-60° C. is blown thereinto to dry the tablets. This series of operations is repeated 20 to 50 times, whereby the monolayer sugar-coated tablet of the invention is produced in around 3-8 hours. Furthermore, when the sugar-coating liquid according to the invention is used to make colored sugar-coated tablet, quite surprisingly all the steps from the sub-coating to polishing can be accomplished with a single sugar-coating liquid. Moreover, even when the sugar coating is conducted by manual pouring, evenly colored sugar-coated tablet is obtained.

Thus, according to the invention sugar-coated tablet is produced in single step, without requiring special skill, and economically very excellent effects such as reduction in consumption of sugar-coating material and in processing time are achieved.
 

Claim 1 of 5 Claims

1. A monolayer sugar-coated tablet coated with a sugar-coating liquid containing 30-54% by weight of sucrose, 2-10% by weight of polyethylene glycol having an average molecular weight between about 7,300 and 9,300, 0.2-2% by weight of polyvinylpyrrolidone having an average molecular weight between about 1,000,000-1,500,000 and pigment, said tablet having a glossy surface.
 

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