Natural rubber blends for floating theophylline beads

Natural rubber (NR)'s value has become increasingly important for human applications. This study prepared NR beads as floating drug delivery system by dripping NR latex into hardening solution to obtain spherical beads. Theophylline was loaded as a model drug. NR latex formed into harden beads suddenly after dripping droplets in acidic medium. These NR beads floated instantly and buoyant in HCl buffer for over 8 h with prolonged theophylline release. Their morphologies, crystallinity and thermal properties were observed using microscope, X-ray diffractometer, and thermogravimetry, respectively. Addition of 100 phr sodium bicarbonate increased drug release owing to liberation of carbon dioxide promoting porous NR matrix. Composite of 50 and 200 phr shellac in NR beads floated in HCl buffer for over 12 h. Moreover, 200 phr shellac efficiently retarded release of theophylline from NR composite beads (lower than 10 % in 8 h), whereby promoting theophylline release in phosphate buffer (pH 6.8) (approximately 80 % in 8 h). NR-shellac beads had greater water sorption (2.5 times) and erosion (4.9 times) in phosphate buffer than in HCl buffer. Thus, NR beads exhibited desirable attributes as floating drug delivery system. Both sodium bicarbonate and shellac modified matrix properties and drug release of NR beads.

Automated summary

In this study, natural rubber (NR) beads were prepared as a floating drug delivery system by dripping NR latex into a hardening solution. The beads showed instant floating and prolonged drug release in HCl buffer. Sodium bicarbonate and shellac were used to modify the properties of the NR matrix and drug release of the beads. The NR-shellac beads exhibited desirable attributes for a floating drug delivery system.