Pentoxifylline increases tissue oxygen delivery in patients, with athe
rosclerotic arterial disease by several mechanisms, including lowering
blood viscosity and increasing erythrocyte flexibility. Since tumor n
eo-vessels are also abnormal and associated with intra-tumoral hypoxia
and, thus, with radiation failure, pentoxifylline might also be usefu
l as a radiation sensitizer. The mouse is frequently used to study suc
h drugs, but the pharmacokinetics of pentoxifylline in the mouse have
not been determined. We investigated this in three separate experiment
s by administering pentoxifylline intraperitoneally, subcutaneously, o
r orally. Plasma was assayed for the parent drug and its metabolites b
y capillary gas chromatography. High plasma levels of pentoxifylline a
nd both major derivatives occurred within several minutes after intrap
eritoneal or subcutaneous injection, but plasma levels were low after
oral administration.