The bilayer floating capsule: a stomach-directed drug delivery system for misoprostol

A bilayer floating dosage unit is proposed to achieve local delivery of misoprostol, a prostaglandin E1 analogue, at the gastric mucosa level. The system is a capsule consisting of a floating layer maintaining the dosage unit buoyant upon the gastric content and a drug layer formulated to act as a sustained-delivery system. The differential design of the two layers allows the optimization of both floating capability and drug release profile. The layers are both composed of a hydrophilic matrix based upon hydroxypropylmethyl cellulose (HPMC). Parameters influencing the release profiles are described. The use of a large capsule increases the gastric residence time (GRT), as it impedes passage through the pylorus opening. gamma-Scintigraphic studies were performed to visualize cohesion of the two layers in vivo and to determine GRT as a function of meal regimen. The average GRTs were 199 +/- 69 min after a single meal (breakfast) and 618 +/- 208 min after a succession of meals.