Shock absorber for a medication delivery device, the device comprising - a container (12) containing medication, - a stopper (14) disposed in said container and mobile for expelling said medication through a dose delivery means (16) , - a piston rod (18) acting on said plug, and means of force that can exert a force on said piston rod, wherein said shock absorber comprises - a tubular sleeve having the opposite proximal and distal ends； said sleeve comprises a compartment (22) formed by a closed end wall at the proximal end of the sleeve and the proximal end of the piston rod which is located at an open end at the distal end of the sleeve； - a fluid disposed within said compartment (22)； - at least one passage (26) formed between said compartment and an annular space (32) between said sleeve and the inner wall of said container (12)； characterized in that - said fluid has a high viscosity； - an elastic and hermetic pad, comprising a waterproof surface (29) disposed against said fluid, the pad being located in said compartment and arranged and designed to cover said at least one step when said elastic pad is in a released position, by means of which, when said force means are activated to exert an applied force on said compartment by means of said piston rod for expelling medicaments, said elastic pad is compressed so that said at least one passage is released, expelling said fluid in a space (32 ) annul between said piston rod (18) and the inner wall of said container (12), thereby creating a damping force, and in which at least one groove (30) having a predetermined length extends axially over the outer circumference surface of the piston rod forming at least one passage between the distal inner circumferential surface of the sleeve and the proximal outer circumferential surface of the piston rod to guide any air trapped inside the compartment.Amortiguador para un dispositivo de administración de medicamentos, comprendiendo el dispositivo - un recipiente (12) que c
