| 摘要 |
857,550. Coated tablets. LOWEY, H. Jan. 25, 1957 [Jan. 25, 1956; July 19, 1956], No. 2762/57. Class 81(1) A plurality of substantially round medically inactive granules to each of which has been applied an impregnating layer of a medically active substance in ethyl cellulose is coated with a plurality of structurally independent ethyl cellulose coatings comprising an actiondelaying layer or layers, the or each said layer containing a total amount of ethyl cellulose not exceeding two per cent of the weight of the inactive granules substantially equally divided among said coatings and each independent coating being not substantially thicker than one tenth of one per cent of the radius of the uncoated granule. As shown (Fig. 2) a granular carrier. 1 of sugar or com starch is impregnated with a solution of say nitroglycerine or aspirin in ethyl cellulose, preferably applied in a plurality (say 12) operations. This forms a medically active layer 2 partly percolating into and partly around the granule. The action delaying layers 3, 4, 5 each comprise 25 independent coatings, each coating being formed from the same weight of ethyl cellulose coating solution. This solution contains a high proportion of solvent (alcohol) and a few per cent of beeswax and castor oil to increase the plasticity and elasticity of the coating: the amount of ethyl cellulose is 15 % by weight of the solution. The coating operation may be carried out in a conventional pan rotating at a much higher speed than usual. Between each coating and after drying the granule carrying the still soft coating is dusted with very fine talc. Using 1 lb. of ethyl cellulose solution per coating and 200 lbs. of inactive granules carrying a medically active impregnating layer it is found that 25 independent coatings form an action delaying layer of 1 hour duration. Thus by forming granules containing different multiples of 25 coatings into a tablet it is possible to control the release of the medicament and to sustain its release over a predetermined time. The coated granules may be tableted with inactive filler granules. |
