The invention relates to the use of plasma treated silicone oil as a coating in a medical injection device (1) comprising a barrel (2) and a stopper (3) in gliding engagement within the barrel, for limiting the number of particles present on the surface of the coating and for limiting the number of particles released in a pharmaceutical composition contained in the injection device. The invention also relates to a medical injection device having: a barrel having an inner surface； a stopper in gliding engagement with the barrel； and a pharmaceutical composition within the medical injection device and in contact with the inner surface of the barrel, the inner surface of the barrel comprising a coating of plasma treated silicone oil in contact with the composition, wherein the plasma treatment of silicone oil reduces the number of particles present on the surface of the coating and the number of particles released into the pharmaceutical composition contained in the medical injection device as compared to silicone oil that is not plasma treated. The invention further relates to a method of treating a medical injection device, the device comprising a barrel having a coated inner surface, a stopper in gliding engagement with the barrel, and to a method of reducing a number of particles present on a surface of a coating or a number of particles released into a pharmaceutical composition contained in such a medical injection device.La présente invention concerne l'utilisation d'huile de silicone traitée au plasma comme revêtement dans un dispositif médical d'injection comprenant un cylindre et un bouchon glissant par contact à l'intérieur du cylindre, destinée à limiter le nombre de particules présentes à la surface du revêtement et à limiter le nombre de particules libérées dans une composition pharmaceutique contenue à l'intérieur du dispositif d'injection. L'invention concerne également un dispositif médical d'injection comprenant : un cylindre ayant une surface interne
