Circulating carrier erythrocytes: slow-release vehicle for an antileukemic drug, cytosine arabinoside.

The human anti-cancer drug Cytosine arabinoside (ana-C) was encapsulated in canine erythrocytes. When these autologous carrier cells were injected into dogs, the drug was slowly released into plasma. Erythrocyte encapsulation increased the plasma half-life of ara-C in dogs about 50-fold over that of the injected free drug. The whole blood half-life of encapsulated drug was 4.6 days and the elimination constant was 0.150 day-1. Erythrocyte encapsulation holds promise as a drug-delivering technique for treatment of some human and animal diseases, particularly with drugs that are highly toxic or have normally short biological half-life. It also could be used to sustain given concentrations of drugs.