Utilization of a single experimental design for the optimization of furosemide modified release tablet formulations.

The loop diuretic drug furosemide is widely used for the treatment of edema in various conditions, such as pulmonary, cardiac and hepatic edema as well as cardiac infarction. Furosemide, due to its poor water solubility and low bioavailability after oral administration of conventional dosage form, is categorized as class IV in the biopharmaceutical classification system.In the case if furosemide, this release profile is responsible for various physiological problems, acute diuresis being the most serious. This adverse effect can be circumvented by the modified release of furosemide from tablet formulations compared to those forms designed for immediate release.In this report, a D-optimal combined experimental design was applied for the development of furosemide containing bilayer and compression coated tablets, aiming at lowering drug's burst release in the acidic environment of the stomach. A D-optimal combined design was selected in order to include all requirements in one design with many levels for the factors examined. The following responses were selected as the ones reflecting better the criteria for the desired drug release: dissolution at 120 min (30-40%), 300 min (60-70%) and 480 min >95%. The new formulations, suggested by the D-optimal combined design, incorporated different grades of Eudragit® polymers (Eudragit® E100 and Eudragit® L100-55), lactose monohydrate and HPMC K15M. The dissolution profile of furosemide from these systems was probed via in vitro dissolution experiments in buffer solutions simulating the pH of the gastrointestinal tract.The results indicate that the use of Eudragit® E100 in conjunction with lactose monohydrate led to 21.32-40.85 % drug release, in the gastric medium, in both compression-coated and bilayer tablets. This is lower than the release of the main stream drug Lasix® (t=120 min, 44.5% drug release), implying longer gastric retention and drug waste minimization.Furosemide's release in the intestinal environment, from compression coated tablets incorporating Eudragit® L100-55 and HPMC K15M in the inner core or in one of the two layers of the bilayer tablets, was delayed, compared to Lasix®.