Five commercially available polymers were evaluated for the preparation of enteric compression coatings utilizing a unique polymer incorporation method, which was part of the granulation process, and which was applicable to all of the polymers with slight modifications. The effect of polymer plasticization, the various methods of polymer incorporation, diluent ingredient properties, and physical factors of the compression coating operation were related wherever possible to the enteric disintegration properties of the manufactured tablets. The compression coating formulations developed of 4 polymers were indicated to be enteric by in uitro disintegration tests, but only 3 of the polymer formulations were clearly enteric according to preliminary ill vivo tests using an X-ray technique and human volunteers.
IIE CONVENTIONAL method of cnteric coating T i n a coating pan is time consuming, empirical, difficult to reproduce, and cumbersome. For large-scale production, newer methods of enteric coating h a w been developed. These include film coating and coinpression coating. The problem of developing highly satisfactory cntcric film coatings, which will be stable in the gastric environment and at thc same time will be impermeable to water and prevent leaching of the drug, is difficult t o resolve. I n the enteric coating field, compression coating appears to have the most potential based on greater precision and reliability of fabrication, in coniparison t o the pan-coating operation which is the other primary enteric coating technique.
Zapapas et al.
(1 j developed an entcric coat.ing formulation of triethaiiolamine, lactose, and magnesium stedratc. James et al.
(2) developed an enteric compression cwdting forrniilation with a carboxylated polymer of vinyl acetate. Swin-Losky obtained a U. S. patent (3) for an enteric comprcssion coating formulation consisting of ,XI to 90y0 of a pharrnaceutically~ available organic acid and a pharmaccutical binder. Miller and Lindner (4) patented an enteric compression coating formulation of penicillin, a water-soluble sulfonamide, and ammotlisted polyvinyl acetate phthalate.
In this study a new method of enteric granulation preparation was utilized which may be more rapid and economical than other conventional comprrssion coating granulation manufacturing procedures. The lactors of formulation, granulation manufaclure, compression properties, and probable mechanisms oi' enteric action were studied for thcir cffccts on the enteric characteristics of the final tahlct coatings.