Gamma scintigraphic studies on guar gum-based compressed coated tablets for colonic delivery of theophylline in healthy volunteers

The purpose of the present study was the development and in vitro/in vivo evaluation of the guar gum-based colon-specific compression-coated tablet formulation of theophylline, which can be used for the treatment of nocturnal asthma. The core tablets containing 100 mg of theophylline were compression coated with various amounts of guar gum. The physical properties of the tablets were tested and in vitro release studies were performed. Samarium oxide (152-Sm) was added to the core tablet as the tracer. Scintigraphy was used to monitor the tablet's movement and distribution through the GI system of six healthy volunteers. In vivo scintigraphic studies showed that the tablets reached the colon at 5,6 and 8 h in three of the six subjects. Theophylline delivery to the terminal ileum or colon can be achieved and the theophylline-guar gum compression coated tablets may be a promising system for the treatment nocturnal asthma. But, more formulation work may be necessary for the determination of the exact coating thickness and the development of optimum formulation.

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