Parenteral formulation of the kappa agonist analgesic, DuP 747, via micellar solubilization

Corticosteroid Microparticles Produced by Supercritical-Assisted Atomization: Process Optimization, Product Characterization, and “in Vitro” Performance

In this work, the production of dexametasone and dexametasone acetate microparticles is proposed using supercritical-assisted atomization (SAA). This process is based on the solubilization of supercritical carbon dioxide in a liquid solution containing the drug; then, the ternary mixture is sprayed through a nozzle and submicroparticles are formed as a consequence of the enhanced atomization. Several process parameters such as different organic solvent (methanol and acetone), solute concentration and flow rate ratio between the liquid solution and carbon dioxide are investigated; their influence is evaluated on the morphology and size of precipitated particles. Spherical corticosteroid particles with mean diameters ranging from 0.5 to 1.2 microm are produced at the optimum operating conditions and narrow particle size distributions (PSDs) have also been obtained. No drug degradation was observed after SAA processing and solvent residues of 300 and 500 ppm for acetone and methanol, respectively, were measured. Drug microparticles produced by SAA can be semi-crystalline or amorphous depending on the process condition; a micronized drug surface area ranging from about 4 to 5 m2/g was also observed. The "in vitro" activity of both untreated and SAA processed glucocorticoids was tested on the release of pro-inflammatory cytokines from stimulated cells. The results shown that SAA-glucocorticoids have retained the activity of the parent untreated compounds and, in the case of dexamethasone, SAA processing improves drug performance.

Solubilization of nicardipine hydrochloride via complexation and salt formation

The solubility behavior of nicardipine (1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic+ ++ acid methyl 2-[methyl(phenyl-methyl)amino]ethyl diester), a calcium channel blocker, used in the treatment of chronic stable angina and mild essential hypertension was investigated. Two techniques that are known to improve solubility, complexation and salt formation, were examined. Concentrations were determined with a specific reversed-phase HPLC assay. The solubility of nicardipine hydrochloride was enhanced exponentially via complexation with aliphatic carboxylic acid buffer systems in a pH dependent fashion. The solubility increased from 5 to 68.6 and 270 mg/mL as the acetate or propionate buffer concentrations, respectively, increased from 0.001 to 5 M, showing a positive deviation from linearity. The conversion of nicardipine hydrochloride to the phosphate salt resulted in a approximately 10-fold solubility improvement. The surface tension of the nicardipine phosphate in water as a function of concentration indicated a critical micelle concentration of 5-6 mg/mL. The critical micelle concentration was greater than the equilibrium solubility of the hydrochloride salt in water, suggesting that a self-association phenomena is responsible for the enhanced solubility of the phosphate salt. Both routes provided potential alternatives for the solubilization of nicardipine.