Natural gums such as karaya and alginate modulate release via gel formation and swelling. Which natural gum is cited?

• A. Eudragit
• B. Karaya gum
• C. HPMC
• D. Ethyl cellulose

Answer: (B)

Natural gums that swell and form a gel layer in contact with fluids slow drug release by creating a barrier through gel formation and diffusion control. Karaya gum is a classic natural gum with strong swelling and gel-forming properties, making it a common release-modifying excipient in matrix systems. Its hydrated gel layer reduces drug diffusion and can also slow erosion, providing sustained release. The other materials listed are not natural gums: Eudragit refers to synthetic acrylic polymers used mainly for coatings or synthetic matrices; HPMC is a semi-synthetic cellulose ether that forms gels but is not a natural gum; Ethyl cellulose is a hydrophobic, water-insoluble polymer that slows release without forming a swelling gel. So karaya gum is the natural gum cited.