Chemistry:Methotrexate

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Short description: Chemotherapy and immunosuppressant medication
Methotrexate
Methotrexate skeletal.svg
Methotrexate-from-xtal-3D-bs-17.png
Clinical data
Pronunciation/ˌmɛθəˈtrɛkˌseɪt, ˌmiː-, -θoʊ-/ (About this soundlisten)[1][2][3]
Trade namesTrexall, Rheumatrex, Otrexup, others[4]
Other namesMTX, amethopterin
AHFS/Drugs.comMonograph
MedlinePlusa682019
License data
Pregnancy
category
  • AU: D
Routes of
administration		By mouth, intravenous (IV), intramuscular (IM), subcutaneous injection (SC), intrathecal
ATC code
Legal status
Legal status
  • AU: S4 (Prescription only)
  • CA: ℞-only
  • UK: POM (Prescription only)
  • US: ℞-only
  • EU: Rx-only
  • In general: ℞ (Prescription only)
Pharmacokinetic data
Bioavailability60% at lower doses, less at higher doses.[5]
Protein binding35–50% (parent drug),[5] 91–93% (7-hydroxymethotrexate)[6]
MetabolismHepatic and intracellular[5]
Elimination half-life3–10 hours (lower doses), 8–15 hours (higher doses)[5]
ExcretionUrine (80–100%), feces (small amounts)[5][6]
Identifiers
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
PDB ligand
Chemical and physical data
FormulaC20H22N8O5
Molar mass454.447 g·mol−1
3D model (JSmol)
  (verify)

Methotrexate (MTX), formerly known as amethopterin, is a chemotherapy agent and immune-system suppressant.[4] It is used to treat cancer, autoimmune diseases, and ectopic pregnancies.[4] Types of cancers it is used for include breast cancer, leukemia, lung cancer, lymphoma, gestational trophoblastic disease, and osteosarcoma.[4] Types of autoimmune diseases it is used for include psoriasis, rheumatoid arthritis, and Crohn's disease.[4] It can be given by mouth or by injection.[4]

Common side effects include nausea, feeling tired, fever, increased risk of infection, low white blood cell counts, and breakdown of the skin inside the mouth.[4] Other side effects may include liver disease, lung disease, lymphoma, and severe skin rashes.[4] People on long-term treatment should be regularly checked for side effects.[4] It is not safe during breastfeeding.[4] In those with kidney problems, lower doses may be needed.[4] It acts by blocking the body's use of folic acid.[4]

Methotrexate was first made in 1947 and initially was used to treat cancer, as it was less toxic than the then-current treatments.[7] In 1956 it provided the first cures of a metastatic cancer.[8] It is on the World Health Organization's List of Essential Medicines.[9][10] Methotrexate is available as a generic medication.[4] In 2020, it was the 113th most commonly prescribed medication in the United States, with more than 5 million prescriptions.[11][12]

Medical uses

Chemotherapy

Methotrexate was originally developed and continues to be used for chemotherapy, either alone or in combination with other agents. It is effective for the treatment of a number of cancers, including solid tumours of breast, head and neck, lung, bladder, as well as acute lymphocytic leukemias, non-Hodgkin's lymphoma, osteosarcoma, and choriocarcinoma and other trophoblastic neoplasms.[4][13]

Autoimmune disorders

Although originally designed as a chemotherapy drug, in lower doses methotrexate is a generally safe and well-tolerated drug in the treatment of certain autoimmune diseases.

Methotrexate is used as a disease-modifying treatment for a number of autoimmune diseases in adults, including rheumatoid arthritis,[14] psoriasis and psoriatic arthritis, reactive arthritis, enteropathic arthritis, myositis, systemic sclerosis, lupus, sarcoidosis, Crohn's disease,[15][16] eczema and many forms of vasculitis. In children, it can be used for juvenile dermatomyositis, juvenile idiopathic arthritis, uveitis and localised scleroderma.[17][18][19]

Methotrexate is one of the first-line therapies for the treatment of rheumatoid arthritis. Weekly doses of 5 to 25mg were found by a Cochrane review to be beneficial for 12-52 weeks duration of therapy, though it is used longer-term in clinical practice. Discontinuation rates are as high as 16% due to adverse effects.[20][17][21][22]

Use of low doses of methotrexate together with NSAIDs such as aspirin or analgesics such as paracetamol is relatively safe in people being treated for rheumatoid arthritis, with appropriate monitoring.[23] Methotrexate is also sometimes used in combination with other conventional DMARDs, such as sulfasalazine and hydroxychloroquine.[24]

Studies and reviews have found that most rheumatoid arthritis patients treated with methotrexate for up to one year had less pain, functioned better, had fewer swollen and tender joints, and had less disease activity overall as reported by themselves and their doctors[citation needed]. X-rays also showed that the progress of the disease slowed or stopped in many people receiving methotrexate, with the progression being completely halted in about 30% of those receiving the drug.[25] Those individuals with rheumatoid arthritis treated with methotrexate have been found to have a lower risk of cardiovascular events such as myocardial infarctions and strokes.[26]

Results of a systematic review exploring the comparative effectiveness of treatments of early rheumatoid arthritis show that treatment efficacy can be improved with combination therapy with anti-TNF or other biologic medications, compared with methotrexate monotherapy.[14][27]

Likewise, a 2016 study found the use of methotrexate, in combination with anti-TNF agents, has been shown to be effective for the treatment of ulcerative colitis.[28]

Methotrexate has also been used for multiple sclerosis[4] and is used occasionally in systemic lupus erythematosus, with tentative evidence to support such use.[29]

During pregnancy

Methotrexate is an abortifacient and is used to treat ectopic pregnancies, provided the fallopian tube has not ruptured.[4][30] Methotrexate with dilation and curettage is used to treat molar pregnancy. Rarely, it is used in combination with mifepristone to abort uterine pregnancies.[31]

Administration

Methotrexate can be given by mouth or by injection (intramuscular, intravenous, subcutaneous, or intrathecal).[4] Doses are usually taken weekly, not daily, to limit toxicity.[4] Routine monitoring of the complete blood count, liver function tests, and creatinine are recommended.[4] Measurements of creatinine are recommended at least every two months.[4]

Folic acid is commonly co-prescribed with methotrexate to minimise the risk of adverse effects.[19]

Adverse effects

The most common adverse effects include hepatotoxicity, stomatitis, blood abnormalities (leukopenia, anaemia and thromboycytopenia), increased risk of infection, hair loss, nausea, reduced appetite, abdominal pain, diarrhoea, fatigue, fever, dizziness, drowsiness, headache, acute pneumonitis and renal impairment.[4][17][32][13] Methotrexate can also cause mucositis.[33]

Methotrexate pneumonitis is a rare complication of therapy, and appears to be reducing in frequency in most recent rheumatoid arthritis treatment trials.[34] In the context of rheumatoid arthritis interstitial lung disease, methotrexate treatment may be associated with a lower incidence of ILD over time.[citation needed]

Methotrexate is teratogenic and it is advised stop taking it at least 4 weeks before becoming pregnant and it should be avoided during pregnancy (pregnancy category X) and while breastfeeding.[35] Guidelines have been updated to state that it is safe for a male partner to take at any point while trying to conceive.[36]

Central nervous system reactions to methotrexate have been reported, especially when given via the intrathecal route (directly into the cerebrospinal fluid), which include myelopathies and leukoencephalopathies. It has a variety of cutaneous side effects, particularly when administered in high doses.[37]

Another little understood but serious possible adverse effect of methotrexate is neurological damage and memory loss.[38] Neurotoxicity may result from the drug crossing the blood–brain barrier and damaging neurons in the cerebral cortex. People with cancer who receive the medication often nickname these effects "chemo brain" or "chemo fog".[38]

Drug interactions

Penicillins may decrease the elimination of methotrexate, so increase the risk of toxicity.[4] While they may be used together, increased monitoring is recommended.[4] The aminoglycosides neomycin and paromomycin have been found to reduce gastrointestinal (GI) absorption of methotrexate.[39] Probenecid inhibits methotrexate excretion, which increases the risk of methotrexate toxicity.[39] Likewise, retinoids and trimethoprim have been known to interact with methotrexate to produce additive hepatotoxicity and haematotoxicity, respectively.[39]

Other immunosuppressants like cyclosporins may potentiate methotrexate's haematologic effects, hence potentially leading to toxicity.[39] NSAIDs have also been found to fatally interact with methotrexate in numerous case reports.[39] Nitrous oxide potentiating the haematological toxicity of methotrexate has also been documented.[39]

Proton-pump inhibitors such as omeprazole and the anticonvulsant valproate have been found to increase the plasma concentrations of methotrexate, as have nephrotoxic agents such as cisplatin, the GI drug colestyramine, and dantrolene.[39]

Mechanism of action

The chemical structures of folic acid and methotrexate highlighting the differences between these two substances (amidation of pyrimidone and methylation of secondary amine)
The coenzyme folic acid (top) and the anticancer drug methotrexate (bottom) are very similar in structure. As a result, methotrexate is a competitive inhibitor of many enzymes that use folates.
Methotrexate (green) complexed into the active site of DHFR (blue)

Methotrexate is an antimetabolite of the antifolate type. It is thought to affect cancer and rheumatoid arthritis by two different pathways. For cancer, methotrexate competitively inhibits dihydrofolate reductase (DHFR), an enzyme that participates in the tetrahydrofolate synthesis.[40][41] The affinity of methotrexate for DHFR is about 1000-fold that of dihydrofolate. DHFR catalyses the conversion of dihydrofolate to the active tetrahydrofolate.[40] Tetrahydrofolate is needed for the de novo synthesis of the nucleoside thymidine, required for DNA synthesis.[40] Also, folate is essential for purine and pyrimidine base biosynthesis, so synthesis will be inhibited. Methotrexate, therefore, inhibits the synthesis of DNA, RNA, thymidylates, and proteins.[40]

For the treatment of rheumatoid arthritis, inhibition of DHFR is not thought to be the main mechanism, but rather multiple mechanisms appear to be involved, including the inhibition of enzymes involved in purine metabolism, leading to accumulation of adenosine; inhibition of T cell activation and suppression of intercellular adhesion molecule expression by T cells; selective down-regulation of B cells; increasing CD95 sensitivity of activated T cells; and inhibition of methyltransferase activity, leading to deactivation of enzyme activity relevant to immune system function.[42][43] Another mechanism of MTX is the inhibition of the binding of interleukin 1-beta to its cell surface receptor.[44] Thereby, it acts as anticytokine.

History

Image shows open bottle of methotrexate drug—one of the first chemotherapeutic drugs used in the early 1950s

In 1947, a team of researchers led by Sidney Farber showed aminopterin, a chemical analogue of folic acid developed by Yellapragada Subbarao of Lederle, could induce remission in children with acute lymphoblastic leukemia. The development of folic acid analogues had been prompted by the discovery that the administration of folic acid worsened leukemia, and that a diet deficient in folic acid could, conversely, produce improvement; the mechanism of action behind these effects was still unknown at the time.[45] Other analogues of folic acid were in development, and by 1950, methotrexate (then known as amethopterin) was being proposed as a treatment for leukemia.[46] Animal studies published in 1956 showed the therapeutic index of methotrexate was better than that of aminopterin, and clinical use of aminopterin was thus abandoned in favor of methotrexate.[citation needed]

In 1951, Jane C. Wright demonstrated the use of methotrexate in solid tumors, showing remission in breast cancer.[47] Wright's group was the first to demonstrate use of the drug in solid tumors, as opposed to leukemias, which are a cancer of the marrow. Min Chiu Li and his collaborators then demonstrated complete remission in women with choriocarcinoma and chorioadenoma in 1956,[48] and in 1960 Wright et al. produced remissions in mycosis fungoides.[49][50]

References

  1. ↑ "methotrexate – definition of methotrexate in English from the Oxford dictionary". OxfordDictionaries.com. https://www.oxforddictionaries.com/definition/english/methotrexate. 
  2. ↑ "Methotrexate". Merriam-Webster Dictionary. https://www.merriam-webster.com/dictionary/methotrexate. 
  3. ↑ "methotrexate". Dictionary.com Unabridged. Random House. https://www.dictionary.com/browse/methotrexate. 
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 "Methotrexate". The American Society of Health-System Pharmacists. https://www.drugs.com/monograph/methotrexate.html. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 "Trexall, Rheumatrex (methotrexate) dosing, indications, interactions, adverse effects, and more". Medscape Reference. WebMD. http://reference.medscape.com/drug/trexall-methotrexate-343201#showall. 
  6. ↑ 6.0 6.1 "Methotrexate in rheumatoid arthritis. An update". Drugs 47 (1): 25–50. January 1994. doi:10.2165/00003495-199447010-00003. PMID 7510620. 
  7. ↑ Drug Discovery: A History. John Wiley & Sons. 2005. p. 251. ISBN 9780470015520. https://books.google.com/books?id=jglFsz5EJR8C&pg=PA251. 
  8. ↑ "Today's anti-cancer tools are ever better wielded". The Economist. 14 September 2017. https://www.economist.com/news/technology-quarterly/21728780-they-are-sharper-too-todays-anti-cancer-tools-are-ever-better-wielded. 
  9. ↑ World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. 2019. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO. 
  10. ↑ World Health Organization model list of essential medicines: 22nd list (2021). Geneva: World Health Organization. 2021. WHO/MHP/HPS/EML/2021.02. 
  11. ↑ "The Top 300 of 2020". https://clincalc.com/DrugStats/Top300Drugs.aspx. 
  12. ↑ "Methotrexate - Drug Usage Statistics". https://clincalc.com/DrugStats/Drugs/Methotrexate. 
  13. ↑ 13.0 13.1 "Methotrexate 2.5 mg Tablets - Summary of Product Characteristics (SmPC) - (emc)". https://www.medicines.org.uk/emc/product/9945/smpc. 
  14. ↑ 14.0 14.1 Drug Therapy for Early Rheumatoid Arthritis: A Systematic Review Update. AHRQ Comparative Effectiveness Reviews. Rockville (MD): Agency for Healthcare Research and Quality (US). 2018. http://www.ncbi.nlm.nih.gov/books/NBK524950/. 
  15. ↑ "Methotrexate: underused and ignored?". Digestive Diseases 30 (Suppl 3): 112–8. 2012. doi:10.1159/000342735. PMID 23295701. 
  16. ↑ "Management of cutaneous lupus erythematosus with low-dose methotrexate: indication for modulation of inflammatory mechanisms". Rheumatol Int 18 (2): 59–62. 1998. doi:10.1515/cclm.1993.31.10.667. PMID 9782534. http://edoc.hu-berlin.de/18452/13106. 
  17. ↑ 17.0 17.1 17.2 Australian Medicines Handbook (2013 ed.). Adelaide: The Australian Medicines Handbook Unit Trust. 2013. ISBN 978-0-9805790-9-3. 
  18. ↑ Joint Formulary Committee (2013). British National Formulary (BNF) (65 ed.). London, UK: Pharmaceutical Press. ISBN 978-0-85711-084-8. https://archive.org/details/bnf65britishnati0000unse. 
  19. ↑ 19.0 19.1 "Methotrexate" (in en-gb). https://www.versusarthritis.org/about-arthritis/treatments/drugs/methotrexate/. 
  20. ↑ "Methotrexate for treating rheumatoid arthritis". The Cochrane Database of Systematic Reviews 2014 (6): CD000957. June 2014. doi:10.1002/14651858.CD000957.pub2. PMID 24916606. 
  21. ↑ "Low-dose methotrexate: a mainstay in the treatment of rheumatoid arthritis". Pharmacological Reviews 57 (2): 163–72. June 2005. doi:10.1124/pr.57.2.3. PMID 15914465. 
  22. ↑ American Rheumatoid Arthritis Guidelines (February 2002). "Guidelines for the management of rheumatoid arthritis: 2002 Update". Arthritis and Rheumatism 46 (2): 328–46. doi:10.1002/art.10148. PMID 11840435. 
  23. ↑ "Safety of non-steroidal anti-inflammatory drugs, including aspirin and paracetamol (acetaminophen) in people receiving methotrexate for inflammatory arthritis (rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, other spondyloarthritis)". The Cochrane Database of Systematic Reviews (11): CD008872. November 2011. doi:10.1002/14651858.CD008872.pub2. PMID 22071858. 
  24. ↑ "Methotrexate and its use in rheumatoid arthritis (RA)" (in en-GB). https://nras.org.uk/resource/methotrexate/. 
  25. ↑ "Methotrexate in rheumatoid arthritis: a quarter century of development". Transactions of the American Clinical and Climatological Association 124: 16–25. 2013. PMID 23874006. 
  26. ↑ "Protective effect of methotrexate in patients with rheumatoid arthritis and cardiovascular comorbidity". Therapeutic Advances in Musculoskeletal Disease 4 (3): 149–57. June 2012. doi:10.1177/1759720X11436239. PMID 22850632. 
  27. ↑ "Comparative Effectiveness of Combining MTX with Biologic Drug Therapy Versus Either MTX or Biologics Alone for Early Rheumatoid Arthritis in Adults: a Systematic Review and Network Meta-analysis". Journal of General Internal Medicine 34 (10): 2232–2245. October 2019. doi:10.1007/s11606-019-05230-0. PMID 31388915. 
  28. ↑ "Methotrexate for Inflammatory Bowel Diseases - New Developments". Digestive Diseases 34 (1–2): 140–6. 1 January 2016. doi:10.1159/000443129. PMID 26981630. 
  29. ↑ "Systemic lupus erythematosus: review of synthetic drugs". Expert Opinion on Pharmacotherapy 16 (18): 2793–806. 2015. doi:10.1517/14656566.2015.1101448. PMID 26479437. "] To date, three small [86–88] RCTs in SLE patients have been published, including in total 76 patients in the active arm". 
  30. ↑ "Current evidence on surgery, systemic methotrexate and expectant management in the treatment of tubal ectopic pregnancy: a systematic review and meta-analysis". Human Reproduction Update 14 (4): 309–19. 2008. doi:10.1093/humupd/dmn012. PMID 18522946. 
  31. ↑ "Medical abortion - Mayo Clinic" (in en). https://www.mayoclinic.org/tests-procedures/medical-abortion/about/pac-20394687. 
  32. ↑ "BNF is only available in the UK". https://www.nice.org.uk/bnf-uk-only. 
  33. ↑ "Methotrexate-induced oral mucositis and salivary methotrexate concentrations". Cancer Chemotherapy and Pharmacology 2 (3): 225–226. 1 September 1979. doi:10.1007/BF00258300. PMID 313282. 
  34. ↑ "Methotrexate-Associated Pneumonitis and Rheumatoid Arthritis-Interstitial Lung Disease: Current Concepts for the Diagnosis and Treatment". Frontiers in Medicine 6: 238. 2019. doi:10.3389/fmed.2019.00238. PMID 31709258. 
  35. ↑ "Use of methotrexate in young patients with respect to the reproductive system". Clinical and Experimental Rheumatology 28 (5 Suppl 61): S80-4. 1 September 2010. PMID 21044438. 
  36. ↑ "Executive Summary: British Society for Rheumatology guideline on prescribing drugs in pregnancy and breastfeeding: immunomodulatory anti-rheumatic drugs and corticosteroids". Rheumatology 62 (4): 1370–1387. November 2022. doi:10.1093/rheumatology/keac558. PMID 36318965. 
  37. ↑ "Three cases of toxic skin eruptions associated with methotrexate and a compilation of methotrexate-induced skin eruptions". Dermatology Online Journal 12 (7): 15. December 2006. doi:10.5070/D30NQ2C0BX. PMID 17459301. 
  38. ↑ 38.0 38.1 "Lost in the fog: understanding "chemo brain"". Nursing 39 (8): 42–5. August 2009. doi:10.1097/01.nurse.0000358574.56241.2f. PMID 19633502. 
  39. ↑ 39.0 39.1 39.2 39.3 39.4 39.5 39.6 "Methotrexate". Martindale: The Complete Drug Reference. Pharmaceutical Press. 6 January 2014. http://www.medicinescomplete.com/mc/martindale/current/ms-9550-n.htm. 
  40. ↑ 40.0 40.1 40.2 40.3 "Interaction of dihydrofolate reductase with methotrexate: ensemble and single-molecule kinetics". Proceedings of the National Academy of Sciences of the United States of America 99 (21): 13481–6. October 2002. doi:10.1073/pnas.172501499. PMID 12359872. Bibcode: 2002PNAS...9913481R. 
  41. ↑ "The molecular perspective: methotrexate". The Oncologist 4 (4): 340–1. August 1999. doi:10.1634/theoncologist.4-4-340. PMID 10476546. http://theoncologist.alphamedpress.org/content/4/4/340.full. 
  42. ↑ "Recent insights in the pharmacological actions of methotrexate in the treatment of rheumatoid arthritis". Rheumatology 47 (3): 249–55. March 2008. doi:10.1093/rheumatology/kem279. PMID 18045808. 
  43. ↑ "Increased peripheral blood B-cells expressing the CD5 molecules in association to autoantibodies in patients with lupus erythematosus and evidence to selectively down-modulate them". Biomedicine & Pharmacotherapy 58 (5): 338–43. June 2004. doi:10.1016/j.biopha.2004.04.010. PMID 15194170. 
  44. ↑ "Mechanism of action of methotrexate: experimental evidence that methotrexate blocks the binding of interleukin 1 beta to the interleukin 1 receptor on target cells". European Journal of Clinical Chemistry and Clinical Biochemistry 31 (10): 667–74. October 1993. doi:10.1515/cclm.1993.31.10.667. PMID 8292668. 
  45. ↑ "Methotrexate: historical aspects". Methotrexate. Basel: Birkhäuser. 2000. ISBN 978-3-7643-5959-1. https://books.google.com/books?id=VCAFHzHAotsC. [page needed]
  46. ↑ "Treatment of acute leukemia with amethopterin (4-amino, 10-methyl pteroyl glutamic acid)". Acta Haematologica 4 (3): 157–67. September 1950. doi:10.1159/000203749. PMID 14777272. 
  47. ↑ "An evaluation of folic acid antagonists in adults with neoplastic diseases: a study of 93 patients with incurable neoplasms". Journal of the National Medical Association 43 (4): 211–40. July 1951. PMID 14850976. 
  48. ↑ "Effect of methotrexate therapy upon choriocarcinoma and chorioadenoma". Proceedings of the Society for Experimental Biology and Medicine 93 (2): 361–6. November 1956. doi:10.3181/00379727-93-22757. PMID 13379512. 
  49. ↑ "Remissions produced with the use of Methotrexate in patients with mycosis fungoides". Cancer Chemotherapy Reports 9: 11–20. November 1960. PMID 13786791. 
  50. ↑ "Observations on the Use of Cancer Chemotherapeutic Agents in Patients With Mycosis Fungoides". Cancer 17 (8): 1045–62. August 1964. doi:10.1002/1097-0142(196408)17:8<1045::AID-CNCR2820170811>3.0.CO;2-S. PMID 14202592. 

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