Pentoxifylline-D6 is intended for use as an internal standard for the quantification of pentoxifylline by GC- or LC-MS. Pentoxifylline is a hemorrheologic agent. It increases the deformability of washed isolated human erythrocytes when used at a concentration of 100 µM. Pentoxifylline (1, 2, and 3 mM) inhibits ADP-induced platelet aggregation in isolated human whole blood. It inhibits thrombus formation induced by ADP in a hamster cheek pouch model when administered at doses of 5, 10, and 20 mg/kg. Formulations containing pentoxifylline have been used in the treatment of intermittent claudication.