Development and in vitro-in vivo evaluation of a multiparticulate sustained release formulation of diltiazem

Drug-polymer mixed coating: a new approach for controlling drug release rates in pellets

A new approach to developing a drug-polymer mixed coat for highly water-soluble diltiazem pellets was investigated at different coating levels. Drug layering and the coating procedures were performed using a bottom spray fluidized bed coater. Drug pellets were coated with Eudragit NE40 (NE40) alone and in combination with diltiazem and hydrophilic cellulose derivatives. Dissolution studies revealed that incorporation of hydrophilic substances such as methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), and the drug itself considerably increased the release rates. The release from mixed polymer coatings was fast compared to pellets coated with NE40 only. The major portion of the drug was released in about 2 hours in case of MC and NE40 mixed coat compared to hours from coated pellets containing HPMC or diltiazem. Incorporation of 15% to 25% drug with respect to the polymer coat helped to achieve a drug-release profile at a desirable rate over a 12 hour period. Moreover, the test formulation comprising 25% diltiazem with respect to 7% NE40 had a dissolution profile that matched the commercial product, Herbesser SR capsules. The release of diltiazem from the coated pellets was slightly affected by the pH of dissolution media.

Influence of pluronic F-68 on dissolution and bioavailability characteristics of multiple-layer pellets of nifedipine for controlled release delivery

A multiple-layer design of pellets for nifedipine was developed using pluronic F-68 to enhance dissolution rate. The influence of ratios of nifedipine in the inner layer to that in the outer layer, the ratios of pluronic F-68 to nifedipine in the solid dispersion, and the thickness of the control membrane on dissolution characteristics were investigated. With an increasing ratio of pluronic F-68 to nifedipine, the dissolution rate of nifedipine was gradually promoted and the extent of release was enhanced as well. DSC thermograms illustrate the gradual disappearance or broadening of the nifedipine melting peak with the presence of pluronic F-68. The decrease of the nifedipine ratio in the inner layer and the increase of the ratio of pluronic F-68 to nifedipine in the outer layer can enhance the release of nifedipine. With a fixed nifedipine ratio of 1.5 between the inner layer and the outer layer, increasing the ratio of pluronic F-68 to nifedipine in the outer layer significantly increased the initial release rate of nifedipine. By increasing the nifedipine ratio of the inner layer to the outer layer to 1:1, the increase of coating percentage referenced to the total weight decreased the release rate of nifedipine from the inner layer. The pharmacokinetic bioequivalence between the test product (Cardilate, N-6) and Coracten was found with a multiple-dose oral administration of 20 mg in 12 healthy, normal Chinese male volunteers.

Preparation and in vitro dissolution profile of dual polymer (Eudragit RS100 and RL100) microparticles of diltiazem hydrochloride

A microparticulate dosage form for a highly soluble drug, diltiazem hydrochloride, was formulated with Eudragit RS100 and RL100 using a novel dual polymer technique. A mixture of diltiazem with Eudragit RS100 (low water permeability) in acetone was coacervated into soft polymer microdrops, following which a mixture of diltiazem and RL100 (high water permeability) was added to produce microparticles consisting of both polymers with diltiazem dispersed in the matrix. A second formulation was developed using the same method except using Eudragit RS100 for both steps. For a comparative study, diltiazem, Eudragit RS100 and RL100 were combined together in a single matrix and formulated into microparticles. In vitro drug release profiles using USP paddle dissolution apparatus 2 revealed that dual polymer matrix microparticles containing Eudragit RS100 in the inner and Eudragit RL100 in the outer core exhibit a suitable release profile with an initial release of the drug followed by a plateau level for the test period of 5 h. Differential scanning calorimetric analysis showed no interaction of the drug with the polymers.