At a Glance
Why Get Tested?
To detect and evaluate toxic concentrations of methotrexate
When to Get Tested?
At specific timed intervals after a high dose of methotrexate to monitor blood levels and guide treatment and whenever symptoms suggest methotrexate toxicity
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None, but timing of the sample for testing is important; when having your blood drawn, tell the laboratorian when you took your last dose of methotrexate.
The Test Sample
What is being tested?
Methotrexate is a drug that has been in use since the 1960s to treat childhood acute lymphocytic leukemia, lymphoma, and cancers of the lung, head, neck, and breast. This test measures the amount of methotrexate in the blood.
Methotrexate prevents cells from using folate to make DNA and RNA, slowing growth of new cancer cells. Because it can also deter growth of new skin cells, methotrexate is also used to treat psoriasis. The drug blocks several enzymes involved in the immune system and can minimize joint damage associated with rheumatoid arthritis (RA).
Methotrexate must be carefully monitored. Even when used correctly, it can cause significant side effects. Increased concentrations can be toxic, potentially damaging the liver, kidneys, and lungs and suppressing cell production in the bone marrow.
Methotrexate dosing depends upon the condition being treated. Methotrexate levels in the blood typically rise after a dose and then fall gradually. Methotrexate is eliminated from the body by the kidneys, so any condition that decreases kidney function or interferes with drug clearance has the potential to increase blood concentrations.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed, but timing of the sample for testing is important and a health practitioner may specify collection at a certain number of hours after a methotrexate dose.
Ask a Laboratory Scientist
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
Methotrexate. American Cancer Society. Available online at http://www.cancer.org/treatment/treatmentsandsideeffects/guidetocancerdrugs/methotrexate through http://www.cancer.org. Last revised December 29, 2011. Accessed January 10, 2014.
Methotrexate (Rheumatrex, Trexall). American College of Rheumatology. Available online at http://www.rheumatology.org/Practice/Clinical/Patients/Medications/Methotrexate_(Rheumatrex,_Trexall)/ through http://www.rheumatology.org. Last updated May 2012. Accessed January 10, 2014.
Methotrexate for psoriasis. WebMd. Available online at http://www.webmd.com/skin-problems-and-treatments/psoriasis/methotrexate-for-psoriasis through http://www.webmd.com. Last updated November 9, 2010. Accessed January 10, 2014.
Methotrexate (Injection Route, Subcutaneous Route). Mayo Clinic. Available online at http://www.mayoclinic.org/drugs-supplements/methotrexate-injection-route-subcutaneous-route/description/DRG-20064776 through http://www.mayoclinic.org. Last updated December 1, 2013. Accessed January 10, 2014.
Sources Used in Previous Reviews
(Revised 2009 April 1). Methotrexate. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682019.html. Accessed April 2010.
(Reviewed 2008 September 1). Methotrexate Injection. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682018.html. Accessed April 2010.
(Revised 2009 July). Patient Education, METHOTREXATE – ORAL. Medscape [On-line information]. Available online through http://www.medscape.com. Accessed April 2010.
Rotondo, N. (2008 August 13). When Is it Appropriate to Use Methotrexate for Ectopic Pregnancy in the Emergency Department? Medscape Today [On-line information]. Available online at http://www.medscape.com/viewarticle/576935 through http://www.medscape.com. Accessed April 2010.
Ranganathan, P. (2008 July 14). An Update on Methotrexate Pharmacogenetics in Rheumatoid Arthritis. Medscape Today from Pharmacogenomics. 2008;9(4):439-451. [On-line information]. Available online at http://www.medscape.com/viewarticle/576224 through http://www.medscape.com. Accessed April 2010.
(Updated 2009 November 1). Methotrexate (Oral Route, Injection Route). MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/drug-information/DR600919 through http://www.mayoclinic.com. Accessed April 2010.
Brauna, J. and Rau, R. (2009 July 29). An Update on Methotrexate. Medscape from Curr Opin Rheumatol. 2009;21(3):216-223.[On-line information]. Available online at http://www.medscape.com/viewarticle/706105 through http://www.medscape.com. Accessed April 2010.
Cannon, M. (Updated 2009 August). Methotrexate (Rheumatrex, Trexall). American College of Rhematology [On-line information]. PDF available for download at http://www.rheumatology.org/practice/clinical/patients/medications/methotrexate.pdf through http://www.rheumatology.org. Accessed April 2010.
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 361-364.
Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 462-463.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 1400-1403.