The system consisting of a drug core and an osmotically active substance surrounded by a semipermeable membrane with a laser-drilled orifice for drug exit is called:

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

Answer: (B)

Osmotic-controlled release using a semipermeable membrane pump is what this describes. The drug core contains an osmotically active substance and is encased by a semipermeable membrane with a laser-drilled exit orifice. Water from the GI tract permeates the membrane, creating osmotic pressure that pushes the drug out through the small hole at a relatively constant rate, giving a nearly zero-order release. This system is known as the osmotic release oral system (OROS). It releases independently of pH and GI motility, offering predictable, controlled delivery. It differs from ion-exchange resins (drug release by ion exchange), matrix tablets (diffusion/erosion from a polymer matrix), and spansules (beads releasing by dissolution/diffusion without an osmotic pump).