Circulating Interferon in Rabbits after Administration of Human Interferon by Different Routes

Abstract

SUMMARY Human leucocyte interferon was rapidly cleared from the circulation of rabbits receiving 3 million units intravenously, but the clearance rate was greatly decreased after I h. The early half-time was 13 min and the late half-time 73 rain. No circulating interferon was detected beyond 6 h. Repeated injections did not affect the clearance rate. Intramuscular injection of 3 million units of human or rabbit interferon main- tained a relatively stable interferon level in the serum for I2 h. Higher doses raised the level and prolonged the persistence of circulating interferon. A single intra- muscular injection of 3o million units of human interferon maintained a detectable interferon level in the serum for 48 h. Subcutaneous injections resulted in even longer persistence of measurable interferon in the blood. No interferon was detected in the serum after oral administration of 6 million units of human interferon.