A plug-in connection system for a two-piece plug-in connection, comprising a plug-in connector and a matching mating connector, wherein the plug-in connector includes a latching unit with latching hooks provided thereon, which engage in groove areas on the mating connector. A main balloon and a side balloon are positioned at the distal end portion of the catheter shaft. The flexible contact element is protected from damage by prohibiting access to its leading edge. The interference portion can have an abutment surface configured to blockingly engage the base member proximate the lower opening to the receiving passage. The resolution agent is employed in special concentration conditions, which provides stability, reproducibility and high enantiomeric purity to the precipitated diasteromer salt, making feasible the industrial production of the S-cetamine and its pharmaceutically acceptable salts.