Device for administering a fluid without a needle, comprising a cylinder (16, 116) which has open dispensing end, a piston which is displaceable between a front and rear end position in the cylinder (16, 116) and is connected to a piston rod that protrudes along a first direction beyond a rear end of the cylinder (16, 116) opposite the open dispensing end and is guided in a receiving block, a nonreturn valve closing the open dispensing end, and a tensioning device which is connected to the piston rod (35, 135) and is arranged in the receiving block, wherein the tensioning device, when the piston is in its front end position, can move the piston rod (35, 135) in a tensioning operation along the first direction until the piston is in its rear end position in order thereby to fill the cylinder (16, 116) with the fluid to be administered and in order to pretension the piston rod (35, 135) towards the open dispensing end, and wherein the tensioning device, when the piston is in its rear end position, can release the piston rod (35, 135) in a dispensing operation, and therefore the piston moves counter to the first direction as far as its front end position because of the applied pretension and, in the process, fluid in the cylinder (16, 116) is dispensed via the nonreturn valve for administering, wherein the cylinder (16, 116) together with the nonreturn valve is in the form of an exchangeable front assembly (13, 14) which is releasably connected to the receiving block, and wherein the device has a nozzle for administering the fluid without a needle, said nozzle being connected to the open dispensing end of the cylinder (16, 116) via the nonreturn valve and being part of the front assembly (13, 14). a cylinder (16, 116) which has open dispensing end, a piston which is displaceable between a front and rear end position in the cylinder (16, 116) and is connected to a piston rod that protrudes along a first direction beyond a rear end of the cylinder (16, 116) opposite the open dispensing end and is guided in a receiving block, a nonreturn valve closing the open dispensing end, and a tensioning device which is connected to the piston rod (35, 135) and is arranged in the receiving block, wherein the tensioning device, when the piston is in its front end position, can move the piston rod (35, 135) in a tensioning operation along the first direction until the piston is in its rear end position in order thereby to fill the cylinder (16, 116) with the fluid to be administered and in order to pretension the piston rod (35, 135) towards the open dispensing end, and wherein the tensioning device, when the piston is in its rear end position, can release the piston rod (35, 135) in a dispensing operation, and therefore the piston moves counter to the first direction as far as its front end position because of the applied pretension and, in the process, fluid in the cylinder (16, 116) is dispensed via the nonreturn valve for administering, wherein the cylinder (16, 116) together with the nonreturn valve is in the form of an exchangeable front assembly (13, 14) which is releasably connected to the receiving block, and wherein the device has a nozzle for administering the fluid without a needle, said nozzle being connected to the open dispensing end of the cylinder (16, 116) via the nonreturn valve and being part of the front assembly (13, 14).