INTRATHECAL METHOTREXATE OVERDOSE

We report two cases of intrathecal methotrexate overdose. A 3-y-old gi rl with acute lymphoblastic leukaemia and a 4-y-old boy with Burkitt's lymphoma were to receive an intrathecal injection of methotrexate aft er completion of intravenous methotrexate infusion. Instead of 12.5 mg , they both received a dose of 125 mg. Both children developed general ized convulsion 3 h after the overdose, but afterwards recovered compl etely. intravenous folinic acid and dexamethasone rescue were employed , but no attempt was made to exchange the cerebrospinal fluid. In addi tion to the staffs failure to check the drug label carefully, the mark ed resemblance of the two dose preparations of methotrexate (50 mg/5 m i and 500 mg/5 mi) may have been contributory.