IMMEDIATE REACTION AFTER METHOTREXATE AND VINCRISTINE WITH URGENT AND PROLONGED INTERMITTENT NEED FOR THE DRUGS

Introduction Immediate reactions to methotrexate (MTX) and vincristine (VCR) are rare. Proposed mechanisms include IgE mediated and anaphylactoid. In a case series, VCR was tolerated after immediate reactions. Given common use of MTX as a first-line chemotherapeutic agent, urgent action and further evaluation is useful. Case Description A 14-year-old male with T cell ALL with CNS involvement received intrathecal MTX followed by intravenous (IV) VCR 6.25 hours later. Both medications were previously tolerated. Fifteen minutes later, the patient received his first dose of IV MTX. Five minutes into the MTX infusion, he experienced throat pruritus, urticarial rash, and lip angioedema. Infusions were discontinued, and diphenhydramine and epinephrine were administered with symptom resolution. Since VCR was tolerated monthly for the past several months, it was administered again without adverse reaction. The patient underwent successful 16-step MTX desensitizations, following premedication with antihistamines, every 2 weeks for 4 doses. Per protocol, patient required IV MTX again 3 months later followed by oral weekly doses in the future. Prior to administration, performed skin prick testing with 0.25, 2.5, and 25 mg/mL MTX and intradermal testing using 0.25, 2.5, and 10 mg/mL MTX, which were negative. Three-step IV MTX graded challenge was performed without adverse reaction. The patient has continued to receive VCR and MTX without reactions. Discussion Immediate reactions to drugs can complicate the chemotherapy course. The reaction could have been due to either VCR or MTX. VCR was tolerated, and without MTX skin testing and subsequent graded challenge, weekly desensitization or second line treatment may have been pursued.