Vincristine in the etiology of toxicity of high‐dose methotrexate therapy

A 14‐year‐old boy received a six‐hour infusion of methotrexate (7 ½ g/M²) with vincristine (2 mg) and citrovorum rescue according to a standard protocol for adjunctive chemotherapy of osteogenic sarcoma. Signs of mild vincristine toxicity occurred from 2–5 days following the infusion; these included jaw pain, decreases in deep tendon reflexes, and a transient ileus. Clearance of serum methotrexate was delayed during the period of ileus and severe methotrexate toxicity was observed.