Preparation and characterization of a sustained release buccoadhesive system for delivery of terbutaline sulfate

Terbutaline sulfate exhibits extensive first pass metabolism and a short elimination half life which makes frequent oral administration of the drug inevitable. A novel buccoadhesive controlled delivery system of the drug can easily overcome the problem. A two-layered core tablet composed of a fast release layer made of mannitol, lactose, PEG and the drug attached to a sustained release layer composed of drug, varying ratios of HPMC, Carbomer 934 (CP), and lactose capped with a buccoadhesive cup coated with an impermeable backing layer was developed. Buccoadhesive cup initially optimized for bioadhesion strength using HPMC and CP with various ratios. Drug transport through buccal membrane indicated a high permeability coefficient (0.00105 cm/sec). All tablets were acceptable with regard to drug contents, thickness, weight variations, hardness and drug content uniformity. The CP:HPMC 2:1 mixture showed the best mucoadhesion properties and was selected as excipient for the cup layer. Swelling index was higher for formulations containing greater amount of lactose and lower percentage of polymers. Fast release layer released its entire content within 15 min while sustained release layer lasted for 12 h. Drug release controlled by a combination of diffusion and chain relaxation mechanism.