Medical devices comprising a syringe barrel, a stopper and a two piece plunger rod are provided. According to one or more embodiments, the two piece plunger rod includes a first plunger rod piece slidably mounted to a second plunger rod piece. The first and second plunger rod pieces include locking elements which allow the length of the plunger rod to be extended during use or injection or compressed during storage or packaging. In one or more embodiments, the medical device is further packaged in a compressed position.
