Methotrexate
Brand Name: Amethoptertin, Folex, Trexall
Classification: Antineoplastic, antirheumatic, immunosuppressant, antimetabolite
Indications
- Trophoblastic neoplasms (choriocarcinoma, Hydatidiform Mole)
- Leukemia
- Breast, head and neck carcinoma
- Severe psoriasis and rheumatoid arthritis unresponsive to conventional therapy
- Ectopic pregnancy
- Lymphosarcoma
- Mycosis fungoides
Methotrexate Pill
Action
Methotrexate works against folic acid metabolism which leads to the inhibition of DNA synthesis and cell production. The drug’s principal mechanism is through competitive inhibition of the enzyme folic acid reductase. For the cells to proliferate and replicate, folic acid must be reduced to tetrahydrofolic acid by this enzyme (folic acid reductase) in the process of DNA synthesis and cellular replication. With the administration of Methotrexate, the reduction of folic acid to tetrahydrofolic acid is inhibited thus, interfering with the tissue cell reproduction.
Because of this function, death of rapidly replicating cells (e.g. cancer cells, choriocarcinoma, leukemia, carcinoma in different body parts and ectopic pregnancy) specifically the malignant ones is made possible. It also has an immunosuppressive activity.
Contraindications
- Known allergic hypersensitivity to the drug
- Pregnancy
Methotrexate has caused fetal death and/or congenital anomalies, therefore, it is not recommended in women of childbearing potential unless there is imperative medical evidence that the benefits can be expected to outweigh the considered risks. Pregnant psoriatic patients should not receive this drug.
- Concomitant use of other drugs that has a hepatotoxic potential (including alcohol) should be avoided.
Adverse Reactions
- Dizziness
- Drowsiness
- Headaches
- Malaise
- Anorexia
- Nausea and vomiting
- Hepatoxicity
- Alopecia
- Ulcerative stomatitis
- Leukopenia
- Chills and fever
- Photosensivity
- Thrombocytopenia
- Hyperurecemia
Dosage
Choriocarcinoma and similar trophoblastic neoplasms
PO/IM: 15-30 mg daily for a 5-day course. The courses are usually repeated 3-5 times as required with a rest period of 1 week or more in between.
Leukemia
PO (adults): 3.3 mg/m2 in combination with Prednisone 60 mg/m2 daily for the induction phase of the therapy.
PO/IM (adults): 20-30 mg/m2 twice weekly for the maintenance phase of the therapy.
IV (adults): 2.5 mg/kg every 2 weeks
IT (adults): 12 mg/m2 or 15 mg
IT (children >3 years): 12 mg
IT (children >3 years): 12 mg
IT (children 2 years): 10 mg
IT (children 1 yr): 8 mg
IT (children <1 yr): 6 mg
Psoriasis
PO (Adults): 2.5-5 mg every 12 hours for 3 doses or every 8 hours for 4 doses once weekly (not to exceed 30 mg/week)
Nursing Considerations
Assessment
Monitor the client taking Methotrexate for:
- Abdominal pain, diarrhea or ulcerative stomatitis.
Therapy may be discontinued with the presence of these toxic effects otherwise, hemorrhagic enteritis and death from intestinal perforation may occur.
- Symptoms of pulmonary toxicity, which may manifest early as a dry and nonproductive cough.
- Symptoms of gout due to increased uric acid. (edema, joint pain)
Laboratory Tests
- CBC (WBC and Platelet)
- Renal function (BUN and Creatinine)
- Hepatic function (AST, ALT, bilirubin)
- Serum Uric Acid concentration
Precautions
Extra precautions in administering Methotrexate should be observed in the following conditions:
- Preexisting liver damage or impaired hepatic function
Methotrexate may be hepatotoxic. Even without previous signs of GI or hematologic toxicity such as liver atrophy, necrosis and cirrhosis. Special caution should be observed in clients with preexisting liver damage or impaired hepatic function.
- Presence of infection, peptic ulcer, ulcerative colitis, geriatric patients or patients with chronic debilitating illnesses.
This drug has an immunosuppressive action. Thus, extreme caution should be observed in patients where immune responses may be vital for healing from a certain disease.
- Impaired renal function
Toxicity and Overdose
If Methotrexate is administered in high doses, the patient must receive Leucovorin Calcium rescue within 24-48 hours to prevent fatal toxicity.
Interventions
- Solutions for injection must be prepared in a biologic cabinet. Gloves, gown and mask are worn while preparing and handling the medication.
- Administer Allopurinol per doctor’s order to decrease uric acid levels.
- Instruct patient to avoid caffeine as it may decrease the efficacy of the drug.
- To prevent hematologic toxicity (platelet levels are decreased) salicylates, NSAIDs, phenytoin, tetracycline and chlorampenicol should be avoided.
images from bedfordlabs.com, johnsonintegrativehealth.com
