METHOTREXATE SODIUM

(meth-oh-trex'ate)

MTX
Classifications: antineoplastic agent; antimetabolite, antifolate; immunosuppressant;
Therapeutic: antineoplastic; immunosuppressant; antifolate
Pregnancy Category: X

Availability

2.5 mg tablets; 2.5 mg/mL, 25 mg/mL injection

Action

Antimetabolite and folic acid antagonist. Blocks folic acid participation in nucleic acid synthesis, thereby interfering with mitotic process. Rapidly proliferating tissues (malignant cells, bone marrow) are sensitive to interference of the mitotic process by this drug.

Therapeutic Effect

In psoriasis, reproductive rate of epithelial cells is higher than in normal cells. Induces remission slowly; use often preceded by other antineoplastic therapies. Also has immunosuppressant effects.

Uses

Principally in combination regimens to maintain induced remissions in neoplastic diseases. Effective in treatment of gestational choriocarcinoma and hydatidiform mole and as immunosuppressant in kidney transplantation, for acute and subacute leukemias and leukemic meningitis, especially in children. Used in lymphosarcoma, in certain inoperable tumors of head, neck, and pelvis, and in mycosis fungoides. Also used to treat severe psoriasis nonresponsive to other forms of therapy, rheumatoid arthritis.

Unlabeled Uses

Psoriatic arthritis, SLE, polymyositis.

Contraindications

Pregnancy (category X), men and women in childbearing age; lactation; hepatic and renal insufficiency; concomitant administration of hepatotoxic drugs and hematopoietic depressants; alcohol; ultraviolet exposure to psoriatic lesions; pre-existing blood dyscrasias.

Cautious Use

Infections; peptic ulcer, ulcerative colitis; very young or old patients; cancer patients with preexisting bone marrow impairment; poor nutritional status.

Route & Dosage

Trophoblastic Neoplasm
Adult: PO/IM 15–30 mg/d for 5 d, repeat for 3–5 courses

Leukemia
Adult: IM/IV Loading Dose 3.3 mg/m²/d PO/IM/IV Maintenance Dose 30 mg/m² weekly in 2 doses

Meningeal Leukemia
Child: Intrathecal 10–15 mg/m²

Lymphoma
Adult: PO 10–25 mg/kg for 4–8 d

Osteosarcoma
Adult: IV 12 g/m², dose repeated at weeks 4, 5, 6, 7, 11, 12, 15, 16, 29, 39, 44, 45

Psoriasis/Rheumatoid Arthritis
Adult: PO 2.5 mg q12h for 3 doses each wk or 7.5 mg once/wk
Child: PO/IM 5–15 mg/m²/wk as single dose or in 3 divided doses 12 h apart

Mycosis Fungoides
Adult: PO/IM 5–50 mg weekly

Administration

Oral

Give 1 h before or 2 h after meals.
Use a test dose (5–10 mg parenterally) 1 wk before therapy for treatment of psoriasis.
Avoid skin exposure and inhalation of drug particles.

Intravenous

Note: Verify correct IV concentration and rate of infusion for administration to children with physician.

PREPARE: Direct: Reconstitute powder vial by adding 2 mL of NS or D5W without preservatives to each 5 mg to yield 2.5 mg/mL. Reconstitute 1 g high-dose vial with 19.4 mL D5W or NS to yield 50 mg/mL. IV Infusion: Further dilute contents of 1 g high-dose vial in D5W or NS.

ADMINISTER: Direct: Give at rate of 10 mg or fraction thereof over 60 sec. IV Infusion: Give over 1–4 h or as prescribed.

INCOMPATIBILITIES Solution/additive: Bleomycin, metoclopramide, prednisolone, ranitidine. Y-site: Chlorpromazine, droperidol, gemcitabine, idarubicin, ifosfamide, midazolam, nalbuphine, promethazine, propofol.

Preserve drug in tight, light-resistant container.

Adverse Effects (≥1%)

CNS: Headache, drowsiness, blurred vision, dizziness, aphasia, hemiparesis; arachnoiditis, convulsions (after intrathecal administration); mental confusion, tremors, ataxia, coma. GI: Hepatotoxicity, GI ulcerations and hemorrhage, ulcerative stomatitis, glossitis, gingivitis, pharyngitis, nausea, vomiting, diarrhea, hepatic cirrhosis. Urogenital: Defective oogenesis or spermatogenesis, nephropathy, hematuria, menstrual dysfunction, infertility, abortion, fetal defects. Hematologic: Leukopenia, thrombocytopenia, anemia, marked myelosuppression, aplastic bone marrow, telangiectasis, thrombophlebitis at intraarterial catheter site, hypogammaglobulinemia, and hyperuricemia. Skin: Erythematous rashes, pruritus, urticaria, folliculitis, vasculitis, photosensitivity, depigmentation, hyperpigmentation, alopecia. Body as a Whole: Malaise, undue fatigue, systemic toxicity (after intrathecal and intraarterial administration), chills, fever, decreased resistance to infection, septicemia, osteoporosis, metabolic changes precipitating diabetes and sudden death, pneumonitis, pulmonary fibrosis.

Diagnostic Test Interference

Severe reactions may occur when live vaccines are administered because of immunosuppressive activity of methotrexate.

Interactions

Drug: Acitretin, alcohol, azathioprine, sulfasalazine increase risk of hepatotoxicity; chloramphenicol, etretinate, salicylates, nsaids, sulfonamides, sulfonylureas, phenylbutazone, phenytoin, tetracyclines, PABA, penicillin, probenecid may increase methotrexate levels with increased toxicity; folic acid may alter response to methotrexate. May increase theophylline levels; cholestyramine enhances methotrexate clearance. Herbal: Echinacea may increase risk of hepatotoxicity. Food: Caffeine >180 mg/d (3–4 cups) may decrease effectiveness for rheumatoid arthritis.

Pharmacokinetics

Absorption: Readily absorbed from GI tract. Peak: 0.5–2 h IM/IV; 1–4 h PO. Distribution: Widely distributed with highest concentrations in kidneys, gallbladder, spleen, liver, and skin; minimal passage across blood–brain barrier; crosses placenta; distributed into breast milk. Metabolism: In liver. Elimination: Primarily in urine. Half-Life: 2–4 h.

Nursing Implications

Assessment & Drug Effects

Lab tests: Obtain baseline liver and kidney function, CBC with differential, platelet count, and chest x-rays. Repeat weekly during therapy. Monitor blood glucose and HbA_1C periodically in diabetics.
Prolonged treatment with small frequent doses may lead to hepatotoxicity, which is best diagnosed by liver biopsy.
Monitor for and report ulcerative stomatitis with glossitis and gingivitis, often the first signs of toxicity. Inspect mouth daily; report patchy necrotic areas, bleeding and discomfort, or overgrowth (black, furry tongue).
Monitor I&O ratio and pattern. Keep patient well hydrated (about 2000 mL/24 h).
Prevent exposure to infections or colds during periods of leukopenia. Be alert to onset of agranulocytosis (cough, extreme fatigue, sore throat, chills, fever) and report symptoms promptly.
Be alert for and report symptoms of thrombocytopenia (e.g., ecchymoses, petechiae, epistaxis, melena, hematuria, vaginal bleeding, slow and protracted oozing following trauma).

Patient & Family Education

Report promptly any abnormal symptoms to physician.
Avoid or moderate alcohol ingestion, which increases the incidence and severity of methotrexate hepatotoxicity.
Practice fastidious mouth care to prevent infection, provide comfort, and maintain adequate nutritional status.
Do not self-medicate with vitamins. Some OTC compounds may include folic acid (or its derivatives), which alters methotrexate response.
Use contraceptive measures during and for at least 8 wk following therapy.
Avoid exposure to sunlight and ultraviolet light. Wear sunglasses and sunscreen.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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