Objective: Evaluate the effect and safety of a desensitization protocol to methotrexate in an adolescent with acute lymphoblastic leukemia L2 (ALL L2) and allergy to methotrexate.
Methods: Desensitization protocol consisted in 2 phases. First phase consisted in premedication with hydrocortisone (IV) 1mgkgdo, cetirizine (PO) 0.2mgkgdo, chlorpheniramine (IV) 0.35mgkgdo and montelukast (PO) 10mgdo at 13, 7 and 1 hour prior to desensitization phase which consisted in an 8 hr scheme of IV infusion of 12 dilutions with increasing concentrations starting at 1:1,000,000 at 30 minutes intervals up to the full dose was completed
Results: Patient was admitted to pediatric intensive care unit and was successfully desensitized, the full protocol was completed as expected, including pre-medication, the desensitization phase lasted 8 hours; at the second dilution (1:100,000) the patient presented nausea, requiring one extra dose of chlorpheniramine, no other adverse reactions were presented in the next 48 hours observation period. He was maintained with 50mg/m2 IV MTX weekly for the full anti-leukemia treatment duration (1-2 years) using the same protocol and stayed out of MTX-related adverse reactions. Today he is followed as an outpatient by our service.
Conclusions: This 12 steps MTX-desensitization protocol was effective and safe. In selected cases of severe allergic reactions to chemotherapeutic agents there where no other equally effective treatment option available, desensitization is effective and safe.