A needle assembly includes a needle member (10) and a blunting member (26), the needle member (10) containing a needle cannula (12), the needle cannula (12) having a puncture tip (14) and having a needle passageway therethrough. The blunting member (26) contains a blunting probe (28) having a blunt end (28a). The needle cannula (12) and the blunting probe (28) are disposed telescopically one within the other without obstructing flow through the needle passageway, and are movable between a sharpened configuration in which the puncture tip (14) of the needle cannula (12) is exposed and a blunted configuration in which the blunt end (28a) of the blunting probe (28) extends beyond the puncture tip (14) to blunt the needle assembly. The assembly may be combined with an accessory device (such as a catheter hub, guide wire, etc.) to produce an apparatus that is lockable in a blunted configuration and that can be released by the associated accessory, or may be configured to be released by manual manipulation.