A metering assembly (4, 4a) for an implantable infusion apparatus comprising: an inlet conduit configured for fluid connection with a pressurized infusate reservoir of the infusion apparatus; an outlet conduit configured for fluid connection with an infusate dispensing member of the infusion apparatus; an infusate accumulator (7, 7a) having an accumulator volume; an inlet valve (9, 9a) in fluid communication with the inlet conduit and the accumulator volume; an outlet valve (10, 10a) in fluid communication with the accumulator volume and the outlet conduit; wherein the inlet valve (9, 9a) and the outlet valve (10, 10a) are both normally closed; and an actuator device configured for actuating the inlet valve (9, 9a) and the outlet valve (10, 10a) between a first state and a second state, wherein in the first state, the inlet valve (9, 9a) is open and the outlet valve (10, 10a) is closed, thereby allowing an infusate flow through the inlet conduit into the accumulator volume while blocking an infusate flow from the accumulator volume through the outlet conduit, and wherein in the second state, the inlet valve (9, 9a) is closed and the outlet valve (10, 10a) is open, thereby allowing an infusate flow from the accumulator volume through the outlet conduit while blocking an infusate flow through the inlet conduit into the accumulator volume; characterized in that the actuator device comprises an actuator (12, 12a) movable between a first position and a second position for alternating actuation of the inlet valve (9, 9a) and the outlet valve (10, 10a) between the first state and the second state, wherein in the first position, the actuator (12, 12a) mechanically actuates the inlet valve (9, 9a) and does not actuate the outlet valve (10, 10a), and wherein in the second position, the actuator (12, 12a) mechanically actuates the outlet valve (10, 10a) and does not actuate the inlet valve (9, 9a). an inlet conduit configured for fluid connection with a pressurized infusate reservoir of the infusion apparatus; an outlet conduit configured for fluid connection with an infusate dispensing member of the infusion apparatus; an infusate accumulator (7, 7a) having an accumulator volume; an inlet valve (9, 9a) in fluid communication with the inlet conduit and the accumulator volume; an outlet valve (10, 10a) in fluid communication with the accumulator volume and the outlet conduit; wherein the inlet valve (9, 9a) and the outlet valve (10, 10a) are both normally closed; and an actuator device configured for actuating the inlet valve (9, 9a) and the outlet valve (10, 10a) between a first state and a second state, wherein in the first state, the inlet valve (9, 9a) is open and the outlet valve (10, 10a) is closed, thereby allowing an infusate flow through the inlet conduit into the accumulator volume while blocking an infusate flow from the accumulator volume through the outlet conduit, and wherein in the second state, the inlet valve (9, 9a) is closed and the outlet valve (10, 10a) is open, thereby allowing an infusate flow from the accumulator volume through the outlet conduit while blocking an infusate flow through the inlet conduit into the accumulator volume; characterized in that the actuator device comprises an actuator (12, 12a) movable between a first position and a second position for alternating actuation of the inlet valve (9, 9a) and the outlet valve (10, 10a) between the first state and the second state, wherein in the first position, the actuator (12, 12a) mechanically actuates the inlet valve (9, 9a) and does not actuate the outlet valve (10, 10a), and wherein in the second position, the actuator (12, 12a) mechanically actuates the outlet valve (10, 10a) and does not actuate the inlet valve (9, 9a).