Treatment of intrathecal methotrexate overdose with folinic acid rescue and lumbar cerebrospinal fluid exchange: A report of two cases.

We report two male cases (4- and 5-years-old) of intrathecal methotrexate overdose. The two boys with acute lymphoblastic leukemia were to receive intrathecal injection of methotrexate. Instead of the prescribed 12 mg, they both received a dose of 120 mg. The initial cerebrospinal fluid samples showed methotrexate concentration of 2.24x10-2M in case 1 and 1.32x10-2M in case 2. The cases were successfully treated with cerebrospinal fluid (CSF) exchange and intravenous folinic acid rescue. The favorable outcome in our cases suggests that CSF exchange is safe and that folinic acid rescue may be adequate to prevent sequelae in patients subjected to intrathecal MTX overdoses up to 120 mg. We propose CSF exchange and intravenous folinic acid as the mainstay of treatment. In addition to the staff's failure to check the drug label carefully, the marked resemblance of the two dose preparations of MTX may have been contributory.