Which system is also known as a monolith, where the drug is homogeneously dispersed in a rate-controlling medium?

• A. Ion exchange resin
• B. OROS
• C. Matrix tablet
• D. Spansules

Answer: (C)

A monolithic matrix system distributes the drug evenly throughout a single rate-controlling medium, so the release comes from diffusion or erosion through that one continuous polymer matrix. This makes a matrix tablet the best description, since the drug is uniformly dispersed inside the tablet and the matrix itself controls how fast it comes out. Ion-exchange resins release the drug via ion exchange with GI fluids, not through a uniform dispersed matrix. Osmotic release (OROS) uses a membrane and an orifice to pump the drug, not a single monolithic phase. Spansules are multiple small beads inside a capsule, a multiparticulate system rather than one continuous matrix.