Measurements obtained during 3-day courses of high dose methotrexate are used in monitoring drug clearance to ensure appropriate therapy.
Clinical details: 
Methotrexate is an anti-cancer drug used solely or in combination with other anti-cancer drugs for the therapy of leukaemia and other malignancies. The initial high dose is given to the patient intravenously and over the next 72 hours. Methotrexate (~90%) is excreted unchanged via the kidney. Relatively low doses have been used in the treatment of rheumatoid arthritis, sarcoidosis and transplantation therapy. Chronic low dose can cause cirrhosis and reversible increase in ALT. High doses results in metabolites (7-hydroxy MTX) and polyglutamate metabolites accumulates intracellularly. Renal impairment worsens toxicity.
High plasma concentrations (>1 μmol/L) after 48 hours require high dose leucovorin rescue.
Reference range: 

Therapeutic range is not established for low dose group. The lowest measurable range is <0.04 umol/L.

Sample type and Volume required: 
Clotted (yellow SST tube). Serum.
Call in advance: 
Urgent out of hours requests should be pre-arranged and/or discussed with the Consultant on-call.
Turnaround time: 
1 day
Blood Sciences Department-Guy's And St Thomas' Hospital
Result Query: 020 7188 8008
St Thomas' Hospital
North Wing - 5th Floor
Westminster Bridge Road
London SE1 7EH
Contact: 020 7188 9247

Guy's Hospital
Southwark Wing - 4th Floor
Great Maze Pond
London SE1 9RT
Contact: 020 7188 4781
Automated Chemistry Laboratory at Guy's and St Thomas' Clinical Advisory Service
Monday – Friday, 09:00-17:00 h: 07738897061
Out of hours, weekends & bank holidays: find details on Rotawatch on Trust intranet GTi, or contact via GSTT switchboard.
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 07/08/2015