Controlled Release of Cyclosporine from Microspheres

Microspheres containing neutralizing antibodies to tumor necrosis factor-alpha and interleukin-1 beta protect rats from Staphylococcus aureus-induced peritonitis

Previous studies using microencapsulated neutralizing antibodies (NA) to tumor necrosis factor (TNF) and interleukin-1 (IL-1) in combination with gentamicin have demonstrated improved survival in a peritonitis model of gram-negative septic shock. Microencapsulation has been shown to improve the effectiveness of NA by delivering them intracellularly, taking advantage of the natural phagocytic activity of the macrophage. It is the purpose of this study to see if microencapsulated NA to TNF and IL-1 in combination with vancomycin can improve survival compared with NA in solution in Staphlococcus aureus-induced septic shock. Groups of 10 rats received the following treatments: (1) S. aureus plus no treatment, (2) S. aureus plus blank microspheres, (3) S. aureus plus vancomycin, (4) S. aureus plus a microsphere form of NA and vancomycin, (5) S. aureus plus a solution form of NA and vancomycin, (6) S. aureus plus a microsphere form of NA, and (7) S. aureus plus a solution form of NA. Survival was monitored for 5 days, and plasma TNF and IL-1 levels were measured for 48 h after S. aureus administration. All (100%) animals that received the microsphere form of NA plus vancomycin, 20%-70% of the animals that received the microsphere form of NA alone, and 20% of the animals that received antibiotics alone survived for 5 days or more. None of the animals in the no treatment group or blank microsphere treatment group and only 10% of the animals in the solution form of NA plus or minus vancomycin group survived for more than 5 days. Plasma TNF and IL-1 levels were significantly increased after S. aureus treatment. Simultaneous and delayed treatment with the microsphere form of NA plus or minus vancomycin significantly reduced TNF and IL-1 levels, and the solution form of NA significantly reduced only TNF levels after immediate treatment. The survival rate was higher in animals with lower TNF levels and IL-1 levels. The results demonstrate that the microsphere form of cytokine NA is 100% effective in combination with vancomycin in protecting rats from S. aureus-induced peritonitis. The microsphere form was also more efficient in attenuating both TNF and IL-1 levels.

Improved efficacy of a microencapsulated macrophage colony stimulating factor and methotrexate in melanoma

This study examines the effects of a combination therapy of both methotrexate (MTX) and albumin microspheres containing recombinant human macrophage colony-stimulating factor (rhM-CSF) in melanoma tumors. Melanoma tumors were induced in C57BL/6 male mice with subcutaneous injection of B-16 tumor cells. Therapy started once the tumor size reached 0.5 cm in diameter. Mice were divided into several groups, and dosing was carried out daily until death. Group I received MTX solution (2 mg/kg or 15 mg/kg), group II received rhM-CSF solution (100 micrograms), group III received albumin rhM-CSF microspheres (100 micrograms), and groups V-XV received different combinations of both agents daily. The weight, tumor size, and survival time (in days) were recorded. From the results, the control (no rhM-CSF administered) group survived for 11.8 +/- 1.92 days, and the group that received MTX solution survived for 19.4 +/- 5.03 days. However, the group that received both the MTX solution (15 mg/kg) and albumin rhM-CSF microspheres (100 micrograms/kg) demonstrated a significant increase (p < .05) in the survival time (30.4 +/- 3.27 days). The concentrations of cytokines (tumor necrosis factor alpha [TNF-alpha] and interleukin-1 beta [IL-1 beta]) in the different treatment groups were monitored to determine the effect of rhM-CSF on the immune system. The TNF-alpha concentration was significantly higher in the group that received the combination therapy (204 +/- 54.6 pg/ml) versus the control group (31.5 +/- 7.02 pg/ml). The IL-1 beta concentration was significantly higher (p < .05) in the rhM-CSF microsphere (100 micrograms/kg) treated group (62 +/- 17.2 pg/ml) versus the rhM-CSF solution (29.1 +/- 8.7 pg/cc).

Drug delivery systems for cyclosporine: achievements and complications

The review deals with the preparation, properties, and analysis of different kinds of cyclosporine delivery systems, such as solid formulations, liposomes, emulsions and microemulsions and targeted cyclosporine formulations. The review points out a key role of delivery systems in increasing the therapeutic effectiveness of cyclosporine. Comparative studies of the prior marketed formulation, Sandimmune, with a new microemulsion formulation, Neoral, are discussed including some data on clinical development of Neoral.

Surface pressure-area isotherms of mixed cyclosporin-poly(isobutylcyanoacrylate) monolayers spread at the air/water interface

The pi-A isotherms of mixed monolayers of cyclosporin and poly(isobutylcyanoacrylate) (PIBCA) show that the molecular areas of cyclosporin and PIBCA are additive regardless of the pH of the substrate or the physical state of the monolayers. All these mixed films collapse at the same surface pressure; therefore, application of the two-dimensional phase rule implies that cyclosporin and PIBCA are immiscible at the interface. This conclusion may have important implications with regard to the formulation of PIBCA-cyclosporin nanoparticles for cyclosporin administration, though further research in this direction will require consideration of the role played by the coadjuvants used for PIBCA polymerization during nanoparticle formation.

Formation and characterization of cyclosporine-loaded nanoparticles

The commercially available formulations of cyclosporine (cyclosporin A, CyA) are associated with acute hemodynamic changes that result in high nephrotoxicity. Among colloidal vectors, nanoparticles (NPs) are receiving much attention as potential drug carriers that would avoid the therapeutic risks of conventional formulations. Two different mechanisms for obtaining polymeric NPs loaded with CyA were studied with regard to their preparation and physicochemical characterization. Isobutyl-2-cyanoacrylate monomer (IBCA) was polymerized, whereas poly-E-caprolactone (PCL, a preformed polymer) was precipitated; both reactions took place in an aqueous medium containing Pluronic F-68 (polyoxypropylene polyoxyethylene block copolymer) as a surface active agent. The encapsulation efficiencies were 78.49 +/- 5.87 and 84.85 +/- 5.02%, respectively, and they remained stable over a wide range of drug concentrations. The polymeric NP had average sizes of 81 +/- 25 and 95 +/- 25 nm for poly-IBCA and PCL, respectively, as confirmed by photon correlation spectroscopy. Poly-IBCA NPs were built from oligomers with molecular weights of 157 to 2644 that joined to form a polymeric nanomatrix. In vitro activity of the drug and the carrier was tested by inhibition of lymphocyte proliferation induced by Concanavalin A. Drug-loaded PCL NPs and free CyA inhibited lymphocyte proliferation by 91.40 and 86.19%, respectively. However, drug-free NPs also exhibited statistically significant (p < 0.05) immunosuppressive activity.

Analysis of release data in the evaluation of the physical state of progesterone in matrix systems

Ethylene-vinyl acetate microspheres were prepared by an emulsion solvent-evaporation method as sustained delivery carriers of progesterone. Physical state of the drug in the microspheres was affected by drug loading level. As thermal analysis and mathematical release models showed, low payloads of the matrix supported the molecularly dispersed drug. Crystalline drug appeared only as the drug loading level increased. The release process of the crystalline drug produced a porosity increase in the polymeric system; thus, the drug could diffuse through pores and channels. Hence, the porosity of the matrix structure was affected by the payload. This hypothesis could justify the increasing goodness-of-fit of the release data to the square-root model as the drug loading level of the microspheres increased.