Of the group of folate antagonists, methotrexate is the most important in cancer chemotherapy or treatment.
Although its initial use was in the treatment of childhood leukaemia, it is now a primary agent in the treatment of choriocarcinoma osteosarcoma, head and neck carcinoma, psoriasis, rheumatoid arthritis and ectopic pregnancy.
The brand names of methotrexate are Rheumatrel and Trexall.
Methotrexate is a potent inhibitor of dihydrofolate reductase, the enzyme responsible for the reduction of folic acid to tetrahydrofolic acid.
It thus reduces the intracellular pool of reduced folates necessary for thymidylate and purine biosynthesis, resulting in inhibition of
DNA synthesis.
The degree of inhibition of DNA synthesis i.e. the cytotoxicity of the drug, depends on the duration of exposure to specific inhibitory levels of the drug, each tissue manifesting a specific threshold level.
Clinical toxicity of methotrexate observed with conventional dosage includes nausea and vomiting, abdominal pain, stomatitis, haemorrhagic enteritis, and myelosuppression.
Poor risk patients are those with renal function impairment, liver disease or a history of peptic ulcer disease.
Encouraging result,have been reported in the use of high dose regimens for the treatment of certain neoplasia utilizing doses up to 5000mg/m2 IV with leucovorin (citrovorum factor) rescue from drug toxicity.
Leucovorin factor (a commercially available analogue of tetrahydrofolic acid) provides substrate for thymidine symhesis and thus acts as an antidote of methotrexate.
It may be given orally, parenterally and intrathecally. The dose and roule depend on the condition being treated. The dose for choriocarcinoma is 30~60mg/m2 weekly.
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A single dose exhibits cure for a good number of patients. For poor risk patients, other drugs may be added. Any regression of tumour that occurs during the toxic phase of the first cycle warrants additional cycles of the drug.
Methotrexate is also effective in the treatment of mycosis fungoidis, acute lymphoblastic leukaemia, Burkitt’s and other Non-Hodgkin’s lymphoma and head and neck carcinoma.
It has also assumed importance in the combination chemotherapy of osteosarcoma, breast, lung, gastrointestinal and genitourinary cancers.
lntrathecally administered trexall is useful in chemotherapy of meningeal leukaemia and Burkitt’s lymphoma.
COST
A vial of methotrexate cost about #8,000 while 100 tablets of 2.5mg tablet cost about #10,000 Naira.
METHOTREXATE IS USED TO INDUCE AN ABORTION
According to Women on Wave, an abortion with the combined use of Methotrexate and Misoprostol is more effective than the use of Misoprostol alone. Methotrexate can be administered as an injection in your muscle or orally.
If you can find a doctor to do an injection of methotrexate, you should get 50 mg/m2 of methotrexate intramuscularly followed by 800 microgram of misoprostol under the tongue 3-7 days after Rheumatrex.
You can also use Rheumatrex orally (75 mg). Most tablets contain 5 or 10 mg that means you will have to swallow quite a lot of tablets. You can also just drink the fluid in the vials that use used for the injections.
About 3 to 7 days after using methotrxate you have to take Misoprostol 800 microgramme under the tongue for half an hour.
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