A micropump for delivery of medication by infusion, comprising: a pump housing; a piston positioned in the pump housing having a longitudinal piston axis; and a motor adapted to rotate the piston about the piston axis; the pump housing having an axial opening receiving the piston, a first aperture positioned radially with respect to the piston axis and communicating with a reservoir, and a second aperture radially positioned with respect to the piston axis communicating with a cannula; the piston having an eccentric cam surface at one end thereof, said cam surface adapted to sequentially open and close the first aperture and the second aperture at respective rotational positions of the piston; wherein the axial position of the piston inside the pump housing determines a pump volume space; wherein the pump housing is stationary, and further comprising an axial position cam surface on the piston, between the motor and the eccentric cam surface, engaging a stationary member on the pump housing, and adapted to translate the piston axially within the pump housing when the piston rotates characterized in that the first aperture and the second aperture each contain an O-ring seal (34, 34') and a spring loaded valve actuator (28, 28'), each valve actuator (28, 28') having a tip, the tips of both actuators (28, 28') being in clearance with the eccentric cam in a normally closed position, and a spring force on the seals (34, 34') being high enough to ensure that the valve actuators (28, 28') do not open under operating pressures of the micropump, wherein the eccentric cam sequentially biases each actuator (28, 28') upon rotation of the piston, releasing compression on the O-ring seal (34, 34') and permitting fluid flow through the first aperture and the second aperture, respectively. a pump housing; a piston positioned in the pump housing having a longitudinal piston axis; and a motor adapted to rotate the piston about the piston axis; the pump housing having an axial opening receiving the piston, a first aperture positioned radially with respect to the piston axis and communicating with a reservoir, and a second aperture radially positioned with respect to the piston axis communicating with a cannula; the piston having an eccentric cam surface at one end thereof, said cam surface adapted to sequentially open and close the first aperture and the second aperture at respective rotational positions of the piston; wherein the axial position of the piston inside the pump housing determines a pump volume space; wherein the pump housing is stationary, and further comprising an axial position cam surface on the piston, between the motor and the eccentric cam surface, engaging a stationary member on the pump housing, and adapted to translate the piston axially within the pump housing when the piston rotates characterized in that the first aperture and the second aperture each contain an O-ring seal (34, 34') and a spring loaded valve actuator (28, 28'), each valve actuator (28, 28') having a tip, the tips of both actuators (28, 28') being in clearance with the eccentric cam in a normally closed position, and a spring force on the seals (34, 34') being high enough to ensure that the valve actuators (28, 28') do not open under operating pressures of the micropump, wherein the eccentric cam sequentially biases each actuator (28, 28') upon rotation of the piston, releasing compression on the O-ring seal (34, 34') and permitting fluid flow through the first aperture and the second aperture, respectively.