effect of various surfactatnts on release behavior of procainamide HCL from ethylcellulose based matrices

The effect of different kinds of surfactants in various concentrations incorporated in an inert matrix, on the release of procainamide hydrochloride, as a cationic model compound, was investigated in this study. Sodium lauryl sulfate and sodium stearate as anionic surfactants, cetyl pyridinium chloride and cetyltrimethyl ammonium bromide as cationic and span 60 and tween 80 as non-ionic surfactants were selected. Hydrophobic matrices were prepared using procainamide HCl, ethyl cellulose, dicalcium phosphate and different percentages of each surfactant and the dissolution rate of drug from various matrices was determined in pH values1.2 [for 2 h] and 7.2 [up to 10 h]. The results showed that incorporation of anionic surfactants in matrix preparations resulted in a remarkable decrease in the release rate of procainamide HCl [P < 0.05], which was attributed to the formation of a poorly soluble complex between the cationic drug and the anionic surfactant. The formation of complex was confirmed by the precipitation titration test. On the other hand, presence of cationic surfactants considerably increased the drug release rate and it was noted that by raising the percentage of surfactant, a faster drug release rate release was achieved. With span 60 there was no change in drug release rate, probably due to its lower wetting capability. While in the case of tween 80, as a hydrophilic non-ionic surfactant, the drug release rate was increased, although statistically not significant. In general, it seems that the influence of cationic and non-ionic surfactants on drug release rate was in accordance with the ability of each surfactant in wetting the matrices and producing a greater number of channels for the dissolution fluid to leach out the drug. Kinetics evaluation of the release profiles showed that the Higuchi equation is the main model, fitting the data

effect of solvent and crystallization conditions on habit modification of carbamazepine

Physical characteristics of carbamazepine crystals grown from pure ethanol or acetone under different conditions were studied for the morphology of crystals by scanning electron microscope, x-ray powder diffraction and FT-IR, and for thermodynamic properties by differential scanning calorimeter. Also the dissolution behavior and compaction properties of crystals were studied. The results showed that crystallization of carbamazepine using watering-out method produced needle shape crystals while by the other methods such as reducing temperature or solvent evaporation produced polyhedral crystals in alcohol and thin plate-like crystals in acetone. The crystals which were grown from acetone were larger than those from alcohol. Differential scanning calorimetery and x-ray powder diffraction showed no evidence of poly-morphism for carbamazepine crystallized by reducing the temperature or by the solvent evaporation in contrast with the crystals produced by the watering out technique. Crystallization of carbamazepine by different methods especially watering-out technique improved its dissolution rate and compactibility and produced high crushing strength compacts without capping