Antimetabolite/Antineoplastic Agent-- Drugs of this class prevent the growth of abnormal cells and tissues.
Mechanism of Action
Methotrexate is a medication associated with chemotherapy that works against folic acid. It inhibits the enzyme dihydrofolate reductase, that converts folic acid to tetrahydrofolic acid. This causes interference with DNA replication and cell reproduction. Methotrexate is used to treat cancers and lesions associated with psoriasis. It also has been shown to have immunosuppressive qualities and thus has been used in the treatment of rheumatoid arthritis and systemic lupus erythematosus.
Dosage Regimens
| Condition | Information | Oral Dosage |
Rheumatoid arthritis |
Severe; for active RA with insufficient response to first line therapy |
7.5 mg once weekly or |
Wegener’s granulomatosis |
|
5-20 mg/week |
Contraindications
You should not take this medication if you are allergic to methotrexate. You should also not take this medication if you are pregnant or breastfeeding. Patients who have experienced alcoholism, chronic liver disease, preexisting blood abnormailities or immunodeficiency syndromes, should NOT take this medication, unless directed to do so after consultation with their physician.
Common Side Effects
- Kidney dysfunction
- Vasculitis
- Headache
- Drowsiness
- Blindness
- Seizures
- Gastrointestinal disturbances
- Inflammation in the mouth (mucositis)
- Reduced white and red blood cells (leukopenia and anemia) and platelets (thrombocytopenia)
- Liver dysfunction
Drug Interactions
| Drug Name | Interaction |
Aspirin, cyclosporine (Gengraf®, Neoral®, sandimmmune®), sulfa antibiotics, penicillins |
Increases methotrexate toxicity secondary to reduced excretion by the kidneys. |
Ibuprofen (Motrin®), Naproxen (Alleve®, Naprosyn®) |
Increases methotrexate toxicity. |
Azathioprine (Imuran®), sulfasalazineAzulfidine®) |
Increases the risk of liver toxicity. |
Steroids |
May reduce efficacy of methotrexate |
Vaccines: |
May increase the risk of infection secondary to vaccines derived from live viruses |
Patient Instructions
- You should not take this medicine if you are pregnant or breastfeeding, have liver disease or have reduced blood counts or immune dysfunction.
- If you forget to take your medicine or miss a dose, take it as soon as possible. If it is close to the time for your next dose, skip the missed dose and take the medicine on schedule. Do not take extra medicine to make up for missed doses. If you take this medication weekly and miss a dose, skip the missed dose and return to your regular schedule the next week.
- This drug should be stored in a closed container at room temperature, away from heat, moisture and direct light.
