Tablets with material gradients fabricated by three-dimensional printing.

Complex tablets with zero-order drug release characteristics were fabricated using three-dimensional printing processes. The matrix tablets exhibited material gradients in radial direction and had drug-free release-barrier layers on both bases. The content of model drug acetaminophen incorporated in the tablets through premixing reached up to 68% of the tablets' weight. Tablets with ethylcellulose gradients showed acceptable mechanical and pharmacotechnical properties, as indicated by crushing strength, friability, and content uniformity tests. The structure and the gradients of ethylcellulose in the tablets were envisaged through environmental scanning electron microscopy and fluorescence tracing technique. Erosion and dissolution studies in vitro indicated that drug was released via a two-dimensional surface erosion mechanism, and 98% of the drug could be released linearly in 12 h. Tablets with other release-retardation material gradients such as sodium lauryl sulfate, stearic acid, and Eudragit RS-100 showed similar release-retardation effects by different release-retardation mechanisms. Through the printing of release-retardation materials, 3DP processes could easily prepare tablets with high dosage and special design features for furnishing the desired drug release characteristics.