concentration measurements were only available in two cases (patients 1 and 3). Patient 1 had a sirolimus blood concentration of 67.9 μg/L four hours after overdose. Patient 3 underwent serial drug concentration monitoring in order to determine the time for recommencing treatment with sirolimus. The maximum measured whole-blood sirolimus concentration was127.6μg/L 24 h after overdose. The concentration-time profile is shown in Fig 1. The patient did not receive sirolimus again until at least 20 days after the overdose. As sirolimus has an oral bioavailability of 15% (when co-administered with cyclosporine) [1], the intravenous application of 1.1 mg in patient 5 was considered approximately equivalent to an oral dose of 6.7mg (Table 1).