Heparin IV Flush Heparin Lock Prefilled Syringes 5 mL, 60/Box (Rx)Heparin IV Flush Heparin Lock Prefilled Syringes 5 mL is sterile, single dose, disposable, plastic pre filled syringe. The DEVICE consists of a hypodermic syringe with a hypodermic barrel, stopper plunger, plunger rod, tip cap and Heparin Lock Flush Solution USP. Heparin I. V. Flush Syringe. Heparin is an anticoagulant (blood thinner) that prevents the formation of blood clots. Heparin flush is used to flush (clean out) an intravenous (IV) catheter,