Preparation of modified release diltiazem HCl capsule by complexation with ion exchange resin


Background: Diltiazem HCl is a calcium channel blocker drug used in the treatmentof angina pectoris and hypertension.Objective: To prepare a sustained release diltiazem HCl capsule by complexationwith polystyrene sulfonate strong cation exchange resin (dowex®50wx4) as acomplexing and retarding agent.Methods: The effect of stirring time and drug: resin ratio on diltiazem HCl loading ondowex®50wx4 was studied. Drug resin complexes were characterized by FourierTransform Infrared (FT-IR) spectroscopy. The release of drug from the complexeswas examined in pH 1.2 and pH 6.8 separately in comparison with pure drug and withcommercially available sustained release products Tildia® 120mg capsule and BITildiem® 120mg tabletsResults and conclusion: Most efficient loading was obtained using 1:2 and 1:2.5drug:resin ratio with stirring time of 60 and 30 minutes respectively. The resultantcomplexes only retard the release of diltiazem HCl when compared with pure drugwhile the sustained release product was obtained by coating the complex withcarnauba wax and the retardation increased as a function of wax concentration. 20%of wax coated complex gave the release profile approximately similar to the marketedsustained release product of diltiazem HCl, Bi-Tildiem® (Sanofi-France) 120 mgtablets.