Effect of orlistat on blood cyclosporin concentration in an obese heart transplant patient

Objective: We detected markedly decreased cyclosporin blood levels in a hea rt-transplanted patient after the gastrointestinal lipase inhibitor orlista t was accidentally added to the treatment program to control for his obesit y. Therefore, we determined cyclosporin plasma concentration time kinetics with and without orlistat reexposition in this patient. Methods: Plasma concentration time kinetics of whole blood cyclosporin leve ls in an obese heart-transplant patient were measured using a standard mono clonal fluorescence polarisation immunoassay. Results were obtained in hour ly intervals up to 12 h without and with co-therapy of 3 x 120 mg orlistat (Xenical, Roche Ltd., Switzerland). The orlistat re-exposition was started the day before taking blood samples. Results: Cyclosporin trough levels (98 ng/ml vs 52 ng/ml). maximum concentr ations (532 ng/ml vs 74 ng/ml) and the area under the blood drug concentrat ion-time curve (2832 ng h ml(-1) vs 700 ng h ml(-1)) were greatly reduced w ith orlistat. Conclusions: Orlistat markedly decreased blood cyclosporin concentrations, possibly due to an interference with its absorption in the small intestine. To avoid potential dangerous under-immunosuppression, orlistat should not be used in patients taking cyclosporin.