An internal standard for clinical testing of Cyclosporin A by LC-MS/MS. This Certified Spiking Solution® is suitable for critical quantitative applications in clinical and diagnostic testing such as therapeutic drug monitoring assays to ensure patients remain within Cyclosporin A’s narrow therapeutic range. The Snap-N-Spike® format allows laboratories to eliminate weighing operations of these hazardous substances, significantly reducing occupational exposure hazards related to handling of acutely toxic powders, and provides the ability to spike into their matrix of choice just before use.