Subcutaneous administration of carrier erythrocytes: slow release of entrapped agent.

Carrier erythrocytes administered subcutaneously in mice release encapsulated molecules at the injection site and through cells that escape the injection site. One day postinjection, the efflux of encapsulated [14C]sucrose, [3H]inulin, and 51Cr-hemoglobin from the injection site was 45, 55, and 65%, respectively. Intact carrier erythrocytes escaped the injection site and entered the blood circulation carrying with them the encapsulated molecules. Most of the encapsulated [3H]inulin that reached whole blood circulated within erythrocytes. Small but measurable numbers of encapsulated molecules were trapped within lymph nodes. Subcutaneous injection of carrier erythrocytes may allow for limited extravascular tissue targeting of drugs.