A drug pump including a housing, reservoir, access port, flow restrictor mechanism, and refill port. The housing defines a discharge outlet, and maintains the reservoir in fluid communication with the refill port. The access port is fluidly connected to the discharge outlet. The flow restrictor mechanism is fluidly connected between the discharge outlet and the access port, positioned to establish outflow and inflow directions. The flow restrictor mechanism has flow restriction characteristics in the outflow direction that differ from flow restriction characteristics in the inflow direction. The flow restrictor mechanism partially restricts fluid flow in the outflow direction such that a clinician can sense a difference between an available injection rate through the access port as compared to through the refill port. Further, the flow restrictor mechanism does not overtly impede fluid withdrawal procedures via the access port.
