Abstract
A means of providing constant drug delivery of theophylline in vitro from a multiple-unit oral capsule dosage form over a 12-h period and up to 95% release of the total drug content is described. Uniform concave mini-tablets (0.3 cm in diameter × 0.2 cm thick) of theophylline, weighing 20 ± 1 mg, were produced, and evenly film-coated with polymers. Coating was carried out by fluidized-bed technology, using organic solvents and a bottom spray coating method. The fluidization dynamics were optimised for reproducibility and film uniformity. The coating composition consisted of insoluble polymers such as Eudragit RS, Eudragit RL and ethylcellulose-containing soluble channelizing agents such as PEG, Eudragit L, CAP and polysorbate 20. Scanning electron micrographs displayed a smooth continuous film of polymer. The dissolution characteristics of 20 mini-tablets with different coating thicknesses enclosed in hard gelatin capsules were evaluated and a slow-release profile corresponding to 95% of total drug content was achieved. The significance of slight variation in coating composition on drug release has been demonstrated.
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