A syringe assembly, comprising: a syringe barrel having a forward end and a rearward end and being arranged along a longitudinal axis, wherein the syringe barrel comprises a bypass protrusion disposed at an intermediate location of the syringe barrel along the longitudinal axis, wherein the bypass protrusion extends radially outwardly from an outer surface of the syringe barrel and is configured to allow fluid passage between two or more chambers formed within the syringe barrel; a restricting element, moveably supported onto a portion of said syringe assembly and positionable in one of an injection disabling position and an injection enabling position in different operative orientations of said syringe assembly, and wherein said restricting element has a flat portion that extends transversely with respect to said longitudinal axis; a plunger rod assembly displaceable within the syringe barrel and operatively coupled with said restricting element; wherein the plunger rod assembly has a forwardly facing shoulder that extends transversely with respect to said longitudinal axis; the plunger rod assembly having a first restricting feature adapted to cooperate with said restricting element, such that when said restricting element is in said injection disabling position, the plunger rod assembly is permitted to be displaced axially forwardly only up to a certain longitudinal extent relative to said syringe barrel in order to perform medicament mixing, and is prevented from further axial displacement and when said restricting element is in said injection enabling position, the plunger rod assembly is permitted to be further displaced axially forwardly relative to said syringe barrel and relative to said restricting element, wherein in order to position said restricting element in said injection enabling position, said restricting element is displaced rotatably about said longitudinal axis, characterized in that the first restricting feature is formed along a portion of the length of said plunger rod assembly and defines a flat wall, and wherein said restricting element has a slot with a flat edge, whereas said flat edge is guided along said flat wall of said first restricting feature of said plunger rod assembly when said restricting element is positioned in said injection disabling position, and further wherein upon engagement of said forwardly facing shoulder with said flat portion, the restricting element is operative to be rotated about said longitudinal axis and thereby positioned in said injection enabling position. a syringe barrel having a forward end and a rearward end and being arranged along a longitudinal axis, wherein the syringe barrel comprises a bypass protrusion disposed at an intermediate location of the syringe barrel along the longitudinal axis, wherein the bypass protrusion extends radially outwardly from an outer surface of the syringe barrel and is configured to allow fluid passage between two or more chambers formed within the syringe barrel; a restricting element, moveably supported onto a portion of said syringe assembly and positionable in one of an injection disabling position and an injection enabling position in different operative orientations of said syringe assembly, and wherein said restricting element has a flat portion that extends transversely with respect to said longitudinal axis; a plunger rod assembly displaceable within the syringe barrel and operatively coupled with said restricting element; wherein the plunger rod assembly has a forwardly facing shoulder that extends transversely with respect to said longitudinal axis; the plunger rod assembly having a first restricting feature adapted to cooperate with said restricting element, such that when said restricting element is in said injection disabling position, the plunger rod assembly is permitted to be displaced axially forwardly only up to a certain longitudinal extent relative to said syringe barrel in order to perform medicament mixing, and is prevented from further axial displacement and when said restricting element is in said injection enabling position, the plunger rod assembly is permitted to be further displaced axially forwardly relative to said syringe barrel and relative to said restricting element, wherein in order to position said restricting element in said injection enabling position, said restricting element is displaced rotatably about said longitudinal axis, characterized in that the first restricting feature is formed along a portion of the length of said plunger rod assembly and defines a flat wall, and wherein said restricting element has a slot with a flat edge, whereas said flat edge is guided along said flat wall of said first restricting feature of said plunger rod assembly when said restricting element is positioned in said injection disabling position, and further wherein upon engagement of said forwardly facing shoulder with said flat portion, the restricting element is operative to be rotated about said longitudinal axis and thereby positioned in said injection enabling position.