Implants may have an outer rate-controlling membrane for extended release. This feature is associated with which dosage form?

Implants may have an outer rate-controlling membrane for extended release. This feature is associated with which dosage form?

• A. In situ Gels
• B. Implants
• C. Liposomes
• D. Microparticles

Answer: (B)

Extended-release systems often control how fast a drug comes out by having a barrier that regulates the rate at which it can pass. The outer rate-controlling membrane is a design feature most characteristic of implants, where a semipermeable outer layer surrounds a drug core and governs release—water permeates through the membrane and drives the drug out over time, enabling long-term, controlled delivery. In situ gels rely on gel formation in place and release through the gel matrix rather than a fixed outer membrane. Liposomes consist of lipid bilayer vesicles whose release is governed by vesicle permeability, not a surrounding rate-controlling layer. Microparticles may be coated to modify release, but the explicit outer rate-controlling membrane around a core is most strongly associated with implants.

Extended-release systems often control how fast a drug comes out by having a barrier that regulates the rate at which it can pass. The outer rate-controlling membrane is a design feature most characteristic of implants, where a semipermeable outer layer surrounds a drug core and governs release—water permeates through the membrane and drives the drug out over time, enabling long-term, controlled delivery.

In situ gels rely on gel formation in place and release through the gel matrix rather than a fixed outer membrane. Liposomes consist of lipid bilayer vesicles whose release is governed by vesicle permeability, not a surrounding rate-controlling layer. Microparticles may be coated to modify release, but the explicit outer rate-controlling membrane around a core is most strongly associated with implants.