- Start Date
- Expiration Date
- Amethopterin; Mexate
- CPT Codes
- Reference Test
- Transport Info
If specimen will not be sent to SBMF on day collected
– Clot 30 minutes
– Promptly centrifuge 15 minutes
– Immediately transfer serum to separate plastic tube
PROTECT FROM LIGHT (WRAP IN FOIL OR USE AMBER PLASTIC TUBE)
- Fasting Required?
- Patient Instructions
- Reference Range
Monitor therapeutic drug level. Evaluate toxicity.
Methotrexate is an antineoplastic drug used solely or in combination with other antineoplastic drugs for the treatment of leukemia and other diseases. Relatively low doses of methotrexate (approximately 7.5-25 mg/week) have been used in the treatment of nonmalignant diseases such as severe psoriasis, asthma, rheumatoid arthritis, sacroidosis, and transplantation therapy. Intermediate to high doses of methotrexate (approximately 35 mg/m2-12 g/m2) with leucovorin (citrovorum-factor) rescue have been used with favorable results in the treatment of osteogenic sarcoma, leukemia, non-Hodgkin’s lymphoma, lung and breast cancer. The efficacy of methotrexate in the treatment of other tumors such as prostatic cancer is being investigated.No precise relationship between methotrexate serum levels and antineoplastic efficacy has been established, although levels below approximately 0.02 µmol/L were seen as necessary for resumption of DNA synthesis. The correlation between serum methotrexate drug concentration and duration of tumor cell exposure in predicting methotrexate toxicity has been demonstrated. Following a 4-6 hour intravenous methotrexate infusion with dosages ranging from 50 mg/m2-15 g/m2, a patient with a 24-Hour serum concentration of greater than 0.5-1.0 µmol/L, and a 72-hour level greater than 0.2 µmol/L is at an increased risk of toxicity if conventional low-dose leucovorin rescue would be indicated. Toxicity is typically present in the form of myelosuppression, stomatitis, nausea, vomiting, convulsions, and liver and renal abnormalities. Anemia, leukopenia, thrombocytopenia, osteoporosis, skin and mucosal involvement with a fatal outcome have also been reported. Neurotoxicity and leukoencephalopathy are also reported as toxic effects involving methotrexate.