Neomycin inhibits thrombin-stimulated release of inositol 1,4,5-trisphosphate (IP₃), by selectively binding PIP₂, but does not inhibit ³²P incorporation into PI or initiation of DNA synthesis^[1]. Neomycin (10 μM-1 mM) induces considerable release of [³H]arachidonic acid from phosphatidylinositol, phosphatidylcholine and phosphatidylethanolamine in saponin-permeabilized human platelets prelabeled with [³H]arachidonic acid. Moreover, neomycin enhances arachidonic acid release induced by thrombin.