Equis ISSN 2398-2977

Methotrexate

Synonym(s): MTX, Amethopterin

Contributor(s): Graham Munroe, Carla Sommardahl

Introduction

Name

  • Type Trade names in the USA include Trexall, Rheumatrex and Amethopterin.
  • Available as 100 mg and 500 mg bottles of methotrexate solution at 25 mg/ml concentration.
  • Also 2.5 mg tablets.

Class of drug

  • Prescription only human medicine in UK, USA, Canada and Australia.

Description

Chemical name

  • 4-amino-N10-methylpteroyl glutamic acid.

Molecular formula

  • C20H22N805.

Molecular weight

  • 454.45 g/mol.

Physical properties

  • Supplied as a solid powder, which is mixed with sterile water.
  • It is soluble at 19°C/66.2°F.
  • It is also soluble in dimethyl sulfoxide.
  • Tablet formulations are also available.

Storage requirements

  • The powder should be stored at -20°C/-4°F.
  • Tablets can be stored at 25°C/77°F and protected from light.

Uses

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Indications

  • In humans it is used intravenously in the treatment of cancer (acute leukemia, osteogenic sarcoma, non-Hodgkin lymphoma and breast carcinoma), autoimmune disease (rheumatoid arthritis, psoriasis, lupus, sarcoidosis), ectopic pregnancy, and for the induction of medical abortions in early pregnancy.
  • In the horse, it has been used off licence for the treatment of arthritis. This is not based on any equine scientific literature but on the mistaken assumption that because it is used in humans for the treatment of rheumatoid arthritis it will be of use in equine osteoarthritis. Anecdotally it has been used for the treatment of equine high ringbone (osteoarthritis of the proximal interphalangeal joint) and to make racehorses move more freely.
  • It is also reported to be used alongside human recombinant erythropoietins in doping racehorses. It is believed that the methotrexate is given to prevent the doped horse from mounting an immune response to the foreign human recombinant protein.

Administration

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Pharmocokinetics

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Precautions

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Interactions

With other drugs

Adverse Reactions

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Hazlewood G S et al (2016) Methotrexate monotherapy and methotrexate combination therapy with traditional and biologic disease modifying anti-rheumatic drugs for rheumatoid arthritis: A network meta-analysis. Cochrane Database Syst Rev 29, 8 BMJ.
  • Bello T R, Amborski G F & Torbert B J (1973) Effects of the immunosuppressant methotrexate in ponies. Am J Vet Res 34 (10), 1291-1297 PubMed.
  • Ward J M & Whitlock R H (1967) Chemotherapy of equine leukemia with amethopterin. Vet Med Small Anim Clin 62 (10), 1003-1008 PubMed.

Other sources of information


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