Design and evaluation of ph sensitive minitablets for chronotherapeutic delivery of theophylline

A pH-sensitive tablet in capsule system intended to approximate the chronobiology of nocturnal asthma is proposed for site specific release to the colon. The system comprising of Eudragit S-100 coated minitablets was designed for chronotherapeutic delivery of theophylline in view to specifically target the nocturnal peak symptoms of asthma. The drug-loaded core minitablets were produced by wet granulation procedure using alcoholic solution of PVP K 30 as a binder. Different coat weights of Eudragit S-100 were applied to the drug loaded core minitablets in a conventional coating pan to produce the pH sensitive minitablets. SEM revealed a distinct continuous acrylic coat free from cracks or pores. In vitro dissolution studies performed following pH progression method demonstrated that the drug release from the coated minitablets depended on the coat weights applied and pH of the dissolution media. The studies showed that a coat weight of 10% weight gain was sufficient to impart an excellent gastro resistant property to the tablets for effective release of the drug at higher pH values.