A portable pump assembly for medical uses, and more particularly a portable micropump designed for the parenteral administration of medicamentous solutions includes a first module (2) provided with a container (8) designed for cooperating with a second motor module (4), the functioning of the pump being ensured by the assembling of the two modules. The first module (2) is provided with a removable filtering and sterilizing device (3), fastened to the filling septum orifice (10) of the container and including a filtering sterile plug (25) and a needle (28) surrounded by a flexible sleeve (29). A support arm (33) includes a guiding part (34) for guiding the device (3) when piercing the septurn and an anchoring casing (40) closing the housing (39) for the second module (4). The first module (2) with the device (3) is provided in a sterile sealed pouch. The assembly is very easy to use, and aseptic conditions are guaranteed during the filling of the container (8).