Abstract: A medical locking device securely fits onto finger grips of a syringe. The locking device is axially aligned with the syringe along a defined longitudinal axis wherein the syringe receives a plunger. The locking device includes a centrally positioned aperture which receives the shaft of the plunger. A retaining member is positioned around the aperture and receives the finger grips of the syringe by engaging at least three sides of the finger grips. This eliminates shifting of the medical locking device and there are opposed cutting members which are chordally positioned in the aperture. The cutting members taper as fine cutting edges for wedging into the plunger during execution of a locking position. To utilize the device, the user twists the plunger into a locking position so that the cutting members wedge into the plunger. This locking position eliminates and prevents any further plunger movement in either direction along the longitudinal axis.