A lock for an outpatients peripherally inserted central catheter (PICC) line limits access to the catheter by patients seeking to abuse injectable narcotics. The lock has two plastic housing halves which slide together, and which define an interior enclosure which receives the catheter line injection port. The housing halves have overlying flanges, through which a fastener extends to secure the device in a closed configuration. The fastener interacts with the flanges in such a way that it cannot be removed without distorting the device and giving evidence of tampering. A zippered sleeve may be provided which surrounds the line leading to the injection port and which has a pull tab which may be engaged within the housing to further prevent access to the line directly.
