Methotrexate Levels, Serum Test
Methotrexate Levels, Serum Test
The methotrexate serum test evaluates the level of methotrexate in the blood.
Methotrexate is an antimetabolite used to treat various types of cancers, adult rheumatoid arthritis (RA), severe Crohn's disease, and psoriasis. It is also prescribed for patients with organ transplantation due to its anti-inflammatory and immunomodulatory properties.
Methotrexate works differently depending on the condition being treated. As an anticancer agent, it interferes with folate, hindering DNA synthesis and slowing cancer cell growth. In RA, it suppresses the immune system to help minimize the damage to the joints. However, methotrexate has a narrow therapeutic range, with side effects possible even at low doses. At high doses, it can cause toxicity, potentially damaging the liver, kidneys, lungs, and bone marrow. Therefore, careful monitoring is essential when starting methotrexate therapy.
Along with a methotrexate blood test, your doctor may also order tests to monitor complete blood count, blood urea and creatinine to evaluate kidney function and liver parameters to evaluate liver function.
What is Methotrexate Serum Test Used For?
The Methotrexate Serum Test is used
To check methotrexate blood levels and verify if it is within therapeutic range during high-dose therapy
To find out if methotrexate is being cleared properly and reached a safe concentration after treatment
To guide the amount and timing of leucovorin as rescue treatment
Symptoms of Methotrexate toxicity
According to the dose, methotrexate use can have varying side effects At low doses, methotrexate use can cause
Loss of appetite
Nausea and vomiting
Thinning of hair
Soreness in the mouth
Excessive tiredness
Headaches
Diarrhea
More severe signs and symptoms may develop with high doses of methotrexate and include
Jaundice
Increased risk of infection
Bruising and bleeding in the gum and gut (a sign of blood disorder)
Inflammation of pancreas
Fever and chills
Persist cough, chest pain, and difficulty in breathing
Swollen hands, ankles or feet
Blurred vision or sudden loss of vision
Confusion
Preparation for Test
No specific preparation is required for the methotrexate blood test. You can eat or drink as usual. However, it's important to let your doctor know when you last took or were given a dose of methotrexate because the timing of sample collection for testing is crucial.
Interpretation of Test Results
No specific preparation is required for the methotrexate blood test. You can eat or drink as usual. However, it's important to let your doctor know when you last took or were given a dose of methotrexate because the timing of sample collection for testing is crucial.
Interpretation of Test Results
Following a high dose of methotrexate, the serum drug concentration is reported as micromoles per liter (μmol/L), with the criteria indicating potential toxicity as follows:
|
Methotrexate serum concentration after a high dose |
Interpretation |
|
>10 µmol/L at 24 hrs |
Poor drug elimination, indicates methotrexate toxicity |
|
>1 µmol/L at 48 hrs |
High risk of toxicity |
|
>0.1 µmol/L after 72 hours |
High risk of developing toxicity |
|
< 0.1 µmol/L after 72 hours |
No risk of toxicity |
FAQs
What factors can influence the results of the Methotrexate blood test?
A variety of prescription and over-the-counter medications, including salicylates, penicillin, warfarin, valproate, proton pump inhibitors, cyclosporine, cisplatin, aminoglycosides, and neomycin, are known to interact or interfere with the absorption of methotrexate in the body. Thus, taking these drugs can influence the results of the blood test.
When is the methotrexate test requested?
A methotrexate test is typically requested at 24 hours, 48 hours, and 72 hours following the administration of a high dose of the drug. It may also be requested whenever a person has symptoms or signs that suggest methotrexate toxicity.
Why should I take a folate supplement when I am taking methotrexate?
Methotrexate is a folic acid antagonist that reduces folate stores in the body, leading to various side effects. To minimize the likelihood of these side effects, your doctor may suggest folic acid supplementation. It can also prevent abnormalities in your blood work, including abnormal blood counts and liver tests. However, keep in mind that you can still experience nausea and vomiting even if you take folic acid.
Are there any risks involved in the Methotrexate Test?
Being a blood test, there is a slight possibility that you may have swelling, tenderness, slight pain, or excessive bleeding at the site of needle insertion and, on extremely rare occasions, infection. However, most symptoms go away quickly.
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