Injection-molded capsule bodies and caps based on polymer blends for controlled drug delivery

A variety of polymer:polymer blends was used to prepare hot melt extrudates and empty capsules (bodies and caps) by injection-molding using a benchtop extruder (Babyplast). KollidonSR:inulin and Carbothane:inulin blends were investigated. The impact of the blend ratio on the water uptake and dry mass loss kinetics upon exposure to 0.1 MHCl, phosphate buffer pH6.8 and culture medium optionally inoculated with fecal samples from Inflammatory Bowel Disease (IBD) patients were studied. Hot melt extrudates were loaded with up to 60% theophylline, capsules were filled with drug powder. Increasing the inulin content led to increased water uptake and dry mass loss rates, resulting in accelerated drug release from the dosage forms, irrespective of the type of polymer blend. This can be attributed to the higher hydrophilicity/water-solubility of this polymer compared to KollidonSR and Carbothane. Interestingly, the presence of fecal samples in culture medium increased the water uptake and dry mass loss of hot melt extrudates to a certain extent, suggesting partial system degradation by bacterial enzymes. However, these phenomena did not translate into any noteworthy impact of the presence of colonic bacteria on theophylline release from the investigated extrudates or capsules. Hence, drug release can be expected to be independent of the location "small intestine vs. colon" from these dosage forms, which can be advantageous for long term release throughout the entire gastro intestinal tract.