AbstractA prefilled, ready to use, disposable syringe wherein a fluid medicament and a diluent therefor are sealed in two separate telescoping syringe barrels. A medicinal powder is sealed in an outer barrel adjacent the nozzle section by means of a pierceable stopper and the diluent is sealed in an inner barrel between another pierceable stopper and a plunger stopper. A double-pointed cannula is positioned between the two pierceable stoppers by means of a telescoping guide arrangement. Movement of the plunger stopper inwardly in the inner barrel initially effects a piercing of both pierceable stoppers and intermixing of the medicinal powder with the diluent. Continued movement of the plunger stopper will expel the mixed medicament from the syringe.