What Is Intrathecal Methotrexate?

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  • Written By: S. Berger
  • Edited By: Shereen Skola
  • Last Modified Date: 02 September 2019
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    Conjecture Corporation
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Intrathecal methotrexate is an injectable drug meant to combat diseases like cancer, psoriasis, and rheumatoid arthritis. This preparation is for lumbar punctures, so that the drug can be injected into the cerebrospinal fluid (CSF) around the spinal cord. This drug can prevent cancerous leukemia cells from propagating in the spine and brain, and can kill any cancerous cells that have entered the CSF.

The act of injecting intrathecal methotrexate is a complex one, and this form of the drug is only administered by doctors in a clinical setting. After entering the body, this medication inhibits an enzyme needed to produce deoxyribonucleic acid (DNA). Preventing the formation of DNA keeps cancerous cells from reproducing, although other non-cancer cells are prevented from reproducing, as well. Non-cancer tissue may be damaged as a result, which accounts for some of the side effects of this drug.

Side effects of intrathecal methotrexate are somewhat rare, since the medication is localized to the CSF, away from normal tissue in the process of cell division. Oral methotrexate can sometimes cause tissue damage due to its wide distribution, but the main side effect of the intrathecal version is pain surrounding the injection site. Headaches, fatigue, blurred vision, and dizziness may all occur shortly after administration. Children given this drug may have neurological effects such as confusion or altered consciousness, but these tend to disappear on their own accord after a short time.


Despite a usual lack of tissue damage or severe side effects from intrathecal methotrexate, doctors will usually carefully monitor a patient receiving this therapy. Regular tests to ensure proper functioning of the kidneys and liver are often performed, along with blood work to ensure that red and white blood cell counts are within reasonable ranges. Frequent tests can allow doctors to detect if a patient is suffering from toxic levels of this medication, and to change the dosage or provide other therapies quickly.

Doctors must also pay attention to any other medication that a patient is taking, since there are many drugs that can interact with intrathecal methotrexate. Non-steroidal anti-inflammatory drugs like ibuprofen or aspirin can cause severe liver damage in the presence of methotrexate. Certain antibiotics may reduce the rate at which methotrexate is cleared from the body, which can increase the risk of dangerous side effects. Vitamins such as folic acid can make this medication less effective by competing with it for enzyme sites that methotrexate normally affects.



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