Syringe assemblies (100) having a passive disabling system to prevent reuse are provided. In one embodiment, the passive disabling system activates after completion of an injection cycle. An exemplary syringe assembly incorporates a stopper (160) and plunger rod (140) attached in a manner to prevent users from disassembling the syringe prior to completion of the injection cycle. The barrel (120) may also include an annular extension (400) or collar that extends from the proximal end of the barrel. In a specific configuration, the annular extension at least partially envelopes a portion of the thumb press to prevent the user from accessing the thumb press and moving the plunger rod in a proximal direction Syringe assemblies of one or more embodiments also include visual indicators or markers indicating whether a syringe assembly is used or the plunger rod is locked within the barrel.
