Abstract:Fluosol‐DA 20%, a perfluorochemical emulsion consisting of 7 parts perfluorodecalin (FDC) and 3 parts perfluorotripropylamine (FTPA), has been used as an oxygen carrier in clinical studies. The emulsion, however, must be stored frozen because it is not stable for long in a liquid state. To increase the stability of perfluorochemical emulsions, a series of experiments on stability, elimination, and toxicity were conducted on different perfluorochemicals. F‐4‐Methyloctahydroquinoli‐dizine (FMOQ) was selected as the best material. The tissue half‐life of FMOQ in rats was estimated to be 7 days, which is the same as that of FDC, a perfluorochemical in Fluosol‐DA 20%. FMOQ emulsified with a mixture of yolk phospholipid and Pluronic F‐68 was stable at 4d̀C for 6 months. Rats exchange‐transfused to a hematocrit of 4% with this emulsion survived for 13 weeks.Summary:The results of this study indicate that the molecular size of and presence of heteroatoms in the PFCs affect excretion rate and emulsion stability. The presence of heteroatoms in the structure probably increases the emulsion stability. Based on those findings, several kinds of bicyclic amines were studied to find PFCs that have a high excretion rate and form a stable emulsion.FMOQ emulsified with a mixture of 2% Pluronic F‐68 and 2% yolk phospholipid is more stable than Fluosol‐DA 20% during thermal stress and over long‐term storage. This emulsion can be sterilized by heating and can be stored at 4d̀C for>6 months without deterioration. The elimination rate of this compound from the organs is about five times higher than that of FTPA and similar to that of FDC. The half‐life in the tissue of rats given 4 g/kg FMOQ was calculated to be ˜7 days. All of the 10 rats exchange‐transfused with FMOQ emulsion at a hematocrit of 4% survived, and the hematocrit and hemoglobin levels normalized rapidly. Three months after the exchange transfusion, no histological changes were found even in the liver and spleen, although a small amount of FMOQ was detected in these organs.From the results obtained, it is concluded that. FMOQ is the most suitable candidate for a second g