Methotrexate

Chemical Pathology

Notes

High dose methotrexate chemotherapy is used in conjunction with other chemotherapy agents in the treatment of lymphomas and some haematological malignancies.

For patients receiving high dose intravenous methotrexate, methotrexate levels must be checked 48 hours after the start of the infusion and then every 24 hours until methotrexate levels fall to a specified value (check relevant chemotherapy protocol for actual value)

In some patients a more rapid infusion rate is used in which case methotrexate levels must be checked 24 hours after the end of the infusion and then every 24 hours until levels fall to a specified value.

This test is not suitable for patients receiving low dose methotrexate for other reasons e.g. for rheumatoid arthritis or psoriasis.

Sample requirements

• Please inform the laboratory when an infusion is being started (specifying the type of infusion) to ensure that samples are included on the lunchtime Bristol transport run where possible.

For adults, 5 ml of blood taken into a narrow gold top tube (or rust top for the Acute Unit)

Storage/transport

Do not store. Send sample immediately to the laboratory at ambient temperature.

Required information

Relevant clinical details, including date and time of start of infusion and date and time of blood sample.

Turnaround times

Samples are sent for analysis to Bristol Royal Infirmary with results normally available within 24 hours.

Further information

For further information see National Cancer Institute Methotrexate Information

Healthcare professionals: please contact Pharmacy for treatment protocols for high dose methotrexate therapy or refer to specific trial protocols as applicable.