A luer lock adaptor including a housing defining an axis, an internal luer lock element having a threading, the internal luer lock element being located internally of the housing and being rotatably mounted thereto for rotation about the axis relative to the housing, in a manner which permits rotation of the luer lock element relative to the housing in a first rotation direction about the axis and limits rotation of the luer lock element relative to the housing in a second rotation direction about the axis, opposite to the first rotation direction, whereby the location of the internal luer lock element internally of the housing prevents manual access to the internal luer lock element for limiting rotation thereof in the first rotation direction.