THERAPEUTICS
Brands
• Amethopterin, Emthexate, Ledertrexate, Maxtrex, Mexate, MTX, Otrexup, Trexall, Rheumatrex, Metoject
Generic?
• Yes
Class
• Antineoplastic agent, immunosuppressant
Commonly Prescribed for
(FDA approved in bold)
• Treatment of malignancies, including non-Hodgkin lymphoma, gestational choriocarcinoma, head and neck epidermoid cancer, and lung and breast cancer
• Psoriasis
• Rheumatoid arthritis
• Inflammatory myopathies: polymyositis (PM) and dermatomyositis (DM)
• Vasculitis, including Wegener’s granulomatosis
• Relapsing-remitting or chronic progressive multiple sclerosis (MS)
• Primary CNS lymphoma
• Ulcerative colitis or Crohn's disease
• Systemic lupus erythematosus
• Psoriatic arthritis
How the Drug Works
• Inhibits dihydrofolic acid reductase. Prevents synthesis of purine nucleotides and thymidylate. This interferes with DNA synthesis, repair, and replication
How Long Until It Works
• Within a week, but effect on neurological diseases may take months
If It Works
• DM/PM: improves strength, and may allow discontinuation or reduced dose of corticosteroids. Corticosteroids are tapered first. Taper slowly over 6 months if clinical remission occurs
• MS: may reduce relapses and new lesions on MRI
• Other disorders: Improves symptoms and clinical markers of the disease
If It Doesn't Work
• DM/PM: question the diagnosis (inclusion-body myositis, hypothyroidism, muscular dystrophy), rule out corticosteroid-induced myopathy, and evaluate for undiagnosed malignancy (especially in DM). Change to azathioprine
• MS: if clearly not helpful, change to another agent
Best Augmenting Combos for Partial Response or Treatment-Resistance
• Usually used in combination with corticosteroids (to reduce corticosteroid dose) in DM and PM. Occasionally combined with other treatments for the treatment of MS
Tests
• Obtain CBC, liver and renal function tests, and chest x-ray at baseline and at dosage adjustments, or for any clinical symptoms. Use serum level and WBC to assess response to treatment
ADVERSE EFFECTS (AEs)
How the Drug Causes AEs
• Folic acid antagonism
Notable AEs
• Ulcerative stomatitis, nausea, abdominal distress
• Malaise, fatigue, chills and fever, dizziness
• Headache, speech impairment, convusions, encephalopathy
• Rash or photosensitivity
• Elevated liver function tests (up to 15%)