Abstract
Objective: This study was undertaken to formulate a floating drug delivery system of theophylline hydrochloride using different concentrations of a chosen polymer and then investigate how polymer concentration affects buoyancy and drug release properties of the tablets.
 Methods: Hydroxypropyl methylcellulose (HPMC) at different concentration levels of 15% (F1), 20% (F2) and 30% (F3) was used to form the three formulation batches of floating tablets. Wet granulation method was used for the granule preparation while Sodium bicarbonate and citric acid were used as the gas generating agent. The physical properties of the granules and the floating tablets were evaluated. Also determined were the physicomechanical properties, buoyancy and swelling characteristics of the tablets. The in vitro drug release study was carried out according to the USP I (basket method) for 8h in 900 ml 0.1N HCl at 50 rpm. Samples withdrawn at the regular predetermined time were analyzed spectrophotometrically at a wavelength of 271 nm and data obtained statistically analyzed by one-way analysis of variance (ANOVA). The differences between means were considered significant at P<0.05.
 Results: The result showed that polymer (HPMC) concentration significantly (p>0.05) increased swelling index and improved floating lag time, it had no significant effect on the total floating time. Percentage drug release at the end of 8 h was 100%, 98.2% and 96.13% for formulation F1, F2 and F3, respectively. All three formulations followed the Higuchi drug release kinetics model and the mechanism of drug release was the non Fickian diffusion with exponents of 0.46, 0.51 and 0.56 for the respective batch.
 Conclusion: Batch F3 gave a better-controlled drug release and floating properties in comparison to batch F1 and F2 thus Polymer concentration influenced the onset of floating and controlled the release of Theophylline.
Highlights
Oral delivery is the most popular route of drug administration due to its versatility, ease of administration and patient compliance [1]
Drugs with short half-lives and that are absorbed from the gastrointestinal tract (GIT) are, eliminated quickly from systemic circulation after oral administration
Gastric emptying of dosage forms is an extremely variable process, being able to influence the emptying time can be a valuable asset for dosage forms that can reside in the stomach for a longer period of time than the conventional ones [4]
Summary
Oral delivery is the most popular route of drug administration due to its versatility, ease of administration and patient compliance [1]. After oral administration, sustained release dosage forms are retained in the gastrointestinal tract, releasing the drug in a controlled manner, so that its absorption sites in the tract are continuously supplied These drug delivery systems suffer mainly from two physiological events: (i) the unpredictable short gastric emptying time and (ii) the brief gastric retention time. Theophylline is a methylxanthine derivative that is very effective in the treatment of chronic bronchial asthma and bronchospastic reaction It has a narrow therapeutic concentration range (from 1020 μg/ml) with a short half-life, which necessitates frequent dosing with conventional dosage forms [6]
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