Methotrexate is a chemotherapy drug that is used to treat certain types of cancer and leukaemia. When given intrathecally, it prevents leukaemia cells entering the cerebrospinal fluid (CSF) around the spine and brain. It is also used to treat leukaemia found in the CSF. This page from Great Ormond Street Hospital (GOSH) describes intrathecal methotrexate, how it is given and some of the possible side effects.Intrathecal methotrexate is given through a needle which is inserted in one of the spaces between the bones in the lower back into the CSF, usually under general anaesthesia. This is known as a lumbar puncture. When drugs are given in this way, they are said to be given intrathecally.
If your child is having intrathecal methotrexate and oral methotrexate – they should not receive oral methotrexate in the same week as intrathecal methotrexate.
What are the side effects?
This medicine causes very few side effects. When given intrathecally, most of the discomfort is as a result of the method of giving the drug.
Intrathecal methotrexate can occasionally cause headaches, dizziness, tiredness, blurred vision or loss of balance for a few hours. It may help to lie down afterwards. It is recommended children lay on their tummy for at least one hour after an intrathecal procedure as this may help distribution of the methotrexate through the CSF. The place where the needle is inserted may become sore or slightly bruised. Any plaster placed over the lumbar puncture site must be removed within 24 hours.
Up to 15 per cent of children receiving intrathecal methotrexate develop neurological changes including fits, change in level of consciousness, abnormal movements or confusion. These complications usually get better spontaneously and do not recur with further doses which may be safely given.
Unfortunately intrathecal chemotherapy is an essential part of treatment of ALL, and it is not at present possible to remove the risk.
Very rarely severe neurological changes persist, a condition called leucoencephalopathy. This is most likely in children who have had clear evidence of leukaemia in the spinal fluid, and where it has been necessary to treat with radiotherapy as well as methotrexate.
Interactions with other medicines
Some medicines can react with methotrexate, altering how well it works. Always check with your doctor or pharmacist before giving your child any other medicine, including medicines on prescription from your family doctor (GP), medicines bought from a pharmacy (chemist) or any herbal or complementary medicines.