Coated capsules for drug targeting to proximal and distal part of human intestine.

Coated hard capsules are becoming increasingly important for a number of reasons such as administration of new active ingredients, oral vaccination, colon drug delivery or their use in preclinical and clinical trials. The independency of coating composition on capsules filling is the major advantage of this dosage form. In our study, two types of hard capsules (gelatin and hypromellose) were coated by non-aqueous solutions of Eudragit L and S 12.5, respectively, to achieve intestinal and distal ileic drug delivery. Gelatin hard capsules were coated with Eudragit film either directly or using hydroxypropyl cellulose sub-coating prior to the final coating. Hypromellose capsules were coated directly. Coated capsules were evaluated for coating thickness by optical microscope and for dissolution in different pH media. Gelatin capsules do not seem to be suitable for direct coating with Eudragit due to insufficient film adhesion to the smooth capsule surface and a brittleness of formed films. These problems can be solved by hydroxypropyl celullose interlayer application. Hypromellose hard capsules could be directly easily coated with both Eudragit solutions. Dissolution of caffeine from coated capsules showed the potency for enteric delivery in gelatin capsules with interlayer and Eudragit L film in 7.5 and 10.0% concentrations and in hypromellose capsules coated with EudragitL in 5-17.5% coating levels. Gelatine capsules with interlayer and 10% Eudragit S film and hypromellose capsules only with high coating level (20%) provided potential distal ileum targeting of incorporated drug. Eudragit S film sprayed onto hypromellose capsules surface was brittle especially in the junction zone between capsule cap and body. Better plasticity of Eudragit S coating could be probably achieved using a different plasticizer.