A 55-year-old man diagnosed in 2006 with CLL who received immunochemotherapy treatment in 2008 with Rituximab-Cyclophosphamide-Fludarabine, achieving a partial response. In 2011, there was evidence of disease progression and he started second-line treatment with Rituximab 375mg/m2 day 1 of the cycle and Bendamustine 90 mg/m2 days 1 and 2 every 28 days. Four hours after administration of day 1 of the second immunochemotherapy cycle, the patient attended the emergency department with a dysthermic sensation, fever of 38oC and an urticarial reaction with pruritus and scaly erythroderma over 50% of the body surface that persisted for 15 days. It was decided to perform skin tests with bendamustine because of the possibility of an allergic reaction to this cytostatic. The stock solution used was bendamustine 2.5mg/ml, with 1/10, 1/100, 1/1000 and 1/10000 dilutions for intradermal administration.
Given the previous good tolerance to rituximab for 6 cycles, the skin reaction was associated with bendamustine. The toxicoderma was classified as grade 4 according to the Common Toxicity Criteria (version 4.0)9 and reported by yellow card to the Spanish Pharmacovigilance System. Skin tests were negative for all dilutions. However, following the benefit/risk assessment between the severity of the toxicoderma and the potential benefit of bendamustine treatment, it was decided to develop a PD for the administration of the next cycles of bendamustine.
The PD consisted of 12 steps for the administration of the full dose of the drug (186.3mg). The protocol consisted of progressively increasing the infusion rate and drug concentration until the total therapeutic dose was reached. Three solutions A, B, and C were prepared from 1/100, 1/10 and 1/1 dilutions respectively. Each of the solutions was used for four steps, increasing the infusion rate every 15 minutes, so that with each step twice as much drug was administered as in the previous step. In the last step, the rate was kept constant until the total defined dose was administered. Table 1 summarises the solutions and the administration schedule of the desensitisation protocol.

The administration was performed on the haematology ward under medical supervision, with a total duration of 5 hours and 37 minutes. The patient received 6 cycles of immunochemotherapy with bendamustine using this PD with mild skin pruritus but no serious complications.