1) The document discusses the therapeutic drug monitoring of cyclosporine, an immunosuppressant commonly used following organ transplantation. 2) Cyclosporine has variable absorption and significant inter-patient variability requiring therapeutic drug monitoring to maintain trough concentrations between 100-400 mcg/L. 3) Factors like CYP3A inhibitors/inducers and foods can impact cyclosporine levels, requiring dosage adjustments to be made based on concentration monitoring.