Cyclosporine is a potent immunosuppressive drug. It has a narrow therapeutic index, and therefore the measurement of cyclosporine’s blood concentration is essential to obtain optimal therapy. Measurement of the area under the blood concentration-time curve (AUC) is reflective of total drug exposure. However, for organ transplant patients, the measurement of AUC involves many problems and difficulties. Thus, it is more clinically acceptable to use a single blood sample as a surrogate index of total drug exposure. Fifty-four adults bone marrow transplant Iraqi patients were given cyclosporine every 12 h as prophylaxis using Neoral® oral solution. Steady-state blood concentrations were monitored for each patient at zero time and then at 1, 2, 3, 4, 6, 8, 10, and at 12 h post-dosing. Cyclosporine blood levels were determined by using AXSYM automated immuno-analyzer which is a fluorescence polarization immunoassay (FPIA). The present investigation demonstrated the best correlation between C2 and the corresponding AUC0–4h and AUC0–12h compared to other concentrations. After two months of cyclosporine therapy, no unexpected biochemical changes and adverse effects were registered. It is concluded from this study that a single blood sample obtained at 2 h post-dosing (C2) and possibly at 3 h post dosing (C3) are ideal surrogate indexes for reflecting total drug exposure, and therefore may be used in clinical practice for predicting therapeutic and toxic effects of cyclosporine.

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