Porous pellets as drug delivery system.

BACKGROUND: Multiparticulate drug delivery systems, such as pellets, are frequently used as they offer therapeutic advantages over single-unit dosage forms. AIM: Development of porous pellets followed by evaluation of potential drug loading techniques. METHOD: Porous microcrystalline pellets were manufactured and evaluated as drug delivery system. Pellets consisting of Avicel PH 101 and NaCl (70%, w/w) were prepared by extrusion/spheronization. The NaCl fraction was extracted with water and after drying porous pellets were obtained (33.2% porosity). Immersion of the porous pellets in a 15% and 30% (w/v) metoprolol tartrate solution, ibuprofen impregnation via supercritical fluids and paracetamol layering via fluidized bed coating were evaluated as drug loading techniques. RESULTS: Raman spectroscopy revealed that immersion of the pellets in a drug solution and supercritical fluid impregnation allowed the drug to penetrate into the porous structure of the pellets. The amount of drug incorporated depended on the solubility of the drug in the solvent (water or supercritical CO(2)). Drug release from the porous pellets was immediate and primarily controlled by pure diffusion. CONCLUSION: The technique described in this research work is suitable for the production of porous pellets. Drug loading via immersion the pellets in a drug solution and supercritical fluid impregnation resulted in a drug deposition in the entire pellet in contrast to fluid bed layering where drugs were only deposed on the pellet surface.

Porous hydroxyapatite tablets as carriers for low-dosed drugs.

The present study evaluated an innovative technique for the manufacturing of low-dosed tablets. Tablets containing hydroxyapatite and a pore forming agent (50% (w/w) Avicel PH 200/20, 37.5% and 50% corn starch/37.5% sorbitol) were manufactured by direct compression followed by sintering. The influence of pore forming agent (type and concentration), sinter temperature and sinter time on tablet properties was investigated. Sintering (1250 degrees C) revealed tablets with an acceptable friability (<1%). Using 50% (w/w) Avicel PH 200 as pore forming agent resulted in tablets combining the highest porosity (50%) and the highest median pore diameter (5 microm). Aqueous drug solutions (metoprolol tartrate, riboflavin sodium phosphate) were spiked on the tablet surface. The maximum volume of drug solution absorbed was limited (2x100 microl), revealing that these porous carriers were ideal for low dosed formulations. Drug release from the tablets was slow, independent of the drug. To accelerate drug release, tablets were manufactured using a modified gelcasting technique yielding tablets with a median pore size of 60 and 80 microm. Release from these tablets was drastically increased indicating that the permeability of the tablets was influenced by the pore size, shape and connectivity of the porous network. Changing and controlling these parameters made it possible to obtain drug delivery systems providing different drug delivery behaviour.