Alteration of therapeutic efficacy of lipid microspheres incorporating prostaglandin E₁ by mixing with aqueous solution

To clarify whether the therapeutic efficacy of lipid microspheres incorporating prostaglandin E₁ (lipo-PGE₁) is altered when mixed and coinfused with clinical solutions, the original lipo-PGE₁ solution (20 μg/mL) was mixed with three clinical infusion solutions: 0.9% sodium chloride solution, Hartmann's solution, and fat emulsion for parenteral nutrition. These diluted lipo-PGE₁ (2 μg/mL) solutions were administered to rats, and their hemodynamic and antiplatelet effects were examined. Peripheral blood flow was increased by 76 ± 4% from the control level when the lipo-PGE₁ solution diluted with the fat emulsion was administered, while it was increased by 43 ± 6% and 36 ± 7%, respectively, when the lipo-PGE₁ solutions diluted with 0.9% sodium chloride and Hartmann's solution were administered. As for the antiplatelet effects of the lipo-PGE₁ solutions, the progression of digit gangrene in thromboangiitis obliterans (TAO) rats was significantly suppressed by the administration of lipo-PGE₁ solution diluted with the fat emulsion, but it was not suppressed by lipo-PGE₁ solution diluted with 0.9% sodium chloride. These findings indicate that the therapeutic efficacy of lipo-PGE₁ is decreased when it is mixed with an aqueous solution such as 0.9% sodium chloride.