A medical device for delivering a medicament to a patient. The device includes a syringe barrel assembly having a syringe barrel with a plunger movably insertable therein to expel medicament in the barrel. A needle cannula is connected to a needle cannula hub which is slidably arranged in the barrel for moving between an initial position in which the forward tip is exposed and a retracted position in which the forward tip is contained within the barrel. A retainer engages an annular groove defined in an inner surface of the barrel and secures the needle cannula hub at the initial position proximate the front end of the barrel. An urging member is arranged between the front end of the barrel and the needle cannula hub for urging the needle cannula hub toward the retracted position. The retainer is released in response to the application of medicament delivery force when the stopper is in a fully inserted position.
