Effect of sodium alginate chain length and Ca2+ and Al3+ on the release of diltiazem from matrices

Sustaining diltiazem hydrochloride decreases its frequency of daily dosage, side effects and enhances patient compliance. In order to control the release of diltiazem, the effect of sodium alginate, Na Alg., chain length as well as Al3+ and Ca2+ on the drug release was studied. Matrices with various amounts of Na Alg. containing 120mg drug with different amounts of Al3+ and Ca2+ were prepared and the drug release was measured in distilled water using USP II dissolution tester. The amount of dissolved drug was assayed spectrophotometrically. The release data of various matrices was fitted to some kinetic models (Higuchi, Peppas and Weibull). Various amounts of Na Alg. had different effects on drug release. The most sustained formulations (without cations) were matrices containing 100 mg Na Alg. in both 250 and 3500 grade. The percent of drug dissolved in 240 min for matrices containing 100mg alginate 250 cps and 3500 cps were 83.4 and 59.8, respectively. Due to the ability of Al3+ to crosslink with anionic sites of Na Alg, it may sustain the drug release. Although the addition of Al3+ up to 0.25 meq, sustained the drug release, but the amounts more than 0.25 meq increased the release rate. The release pattern of matrices containing Ca2+ was almost comparable to one of drug alone. The release of diltiazem from matrices can be controlled at any desired rate applying suitable Na Alg. grade together with proper amount of Al3+.