Cyclodextrins and their derivatives play an important role in improving the therapeutic efficacy of drugs with poor solubility and/or stability problems. They are capable of alleviating the undesirable properties of drug molecules through the formation of inclusion complexes (1). Hydroxypropyl-b-cyclodextrin (HPbCD) is mainly selected for its higher solubility than other cyclodextrins and this generally results in more extensive solubilization ability toward lipophilic molecules, with a good safety profile (2). Ternary complexes of meloxicam (ME) (a poorly water soluble anti-inflammatory drug) with hydroxypropyl-b--cyclodextrin (HPbCD) and either a hydrophilic polymer, namely, polyvinyl pyrrolidone (PVP) or a basic amino acid such as L-arginine, were prepared by the spray-drying technique. The solubilizing efficiency, physical properties and dissolution behaviour of each ternary system of ME--HPbCD with either PVP or L-arginine were compared with those of the corresponding binary system of ME--HPbCD. Tablets compressed from the ternary system of ME-HPbCD-L-arginine were compared with plain and commercial tablets. Phase solubility experiments suggested the formation of an inclusion complex of A L type. Ternary system of ME-HPbCD-L-arginine exhibited a stability constant 30.3 times higher than the binary system of ME-HPbCD, while the ternary system of ME-HPbCD--PVP increased the stability constant 2.2 times only. The prepared complexes were characterized by scanning electron microscopy, differential scanning calorimetry and infra red spectroscopy. Ternary solid complexes indicated the presence of strong interactions between the components. The dissolution behaviour of ME from different ternary complexes was higher than its dissolution from the binary system. Tablets compressed from ternary complexes of ME-HPbCD-L-arginine highly improved drug release compared to plain and commercial tablets.

Ketoprofen powder was encapsulated with Eudragit RL/RS polymer solutions in isopropanol-acetone 1:1, using a simple and rapid method. Microcapsules were prepared using Eudragit solutions with different RL/RS ratios. The encapsulation process produces free-flowing microcapsules with good drug content and marked decrease in dissolution rate. The retardation in release profile of ketoprofen from microcapsules was a function of the polymer ratio employed in the encapsulation process. In vitro release of ketoprofen from microcapsules either filled in gelatin capsules or compressed into tablets, using calcium sulphate as diluent, confirmed the efficiency of the encapsulation process for preparing prolonged release medication. A capsule formulation with optimum sustained-release profile was suggested.

Trials to induce complex coacervation between two grades Gantrez-AN polymer (G-AN), and Type A gelatin were made. Physical parameters influencing the coacervation process were studied. Maximum coacervation was attained when the pH of the gelatin solution was at 6.8. Increasing the molecular weight of Gantrez decreased the ratio of combination of both polymers. The ratio for optimum coacervation was 1:4 for Gantrez-AN 119-gelatin system and 2:3 for Gantrez-AN 149-gelatin system with total colloid concentration of 2.5 g per cent w/v in both cases. High stirring speed gave almost spherical uniform coacervates. Recovery of the product as water-insoluble discrete units required the use of formaldehyde and isopropanol for coacervate denaturation and flocculation, respectively.

Nitrofurantoin crystals were encapsulated in a Gantrez-gelatin complex coacervation system. The encapsulation process was reproducible and inexpensive and the microcapsules were free flowing and directly compressible into tablets. In vitro release of nitrofurantoin from Gantrez-gelatin microcapsules was studied as a function of the core:coat ratio, the molecular weight of Gantrez and the particle size of the microcapsules. The release of the drug was significantly reduced using G149-gelatin microcapsules of core:coat ratio of 1:2. Release data were examined kinetically and were found to follow a diffusion-controlled model. In vitro release of the drug from the microcapsules filled in capsules and compressed into tablets confirmed the efficiency of the encapsulation process for preparing prolonged release formulations.

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