Trexan Dosage/Direction for Use

Methotrexate should only be prescribed by physicians with expertise in the use of methotrexate and a full understanding of the risks of methotrexate therapy.
The prescriber should ensure that patients or their carers will be able to comply with the once weekly regimen.
Dosage for Cancer Treatment: Fatal cases of intoxication have been reported after administration of incorrectly calculated doses. Health care professionals and patients should be fully informed about toxic effects.
Oral administration: A test dose of 5 - 10 mg parenterally is recommended, one week prior to therapy to detect idiosyncratic adverse events. Low doses not exceeding 30 mg/m² on five successive days. Thereafter an interval of at least two weeks is recommended to allow the bone marrow to recover.
Doses in excess of 100 mg are usually given parenterally, when the injectable preparation should be used. Doses in excess of 70 mg/m² should not be administered without leucovorin rescue (folinic acid rescue) or assay of serum methotrexate levels 24 - 48 hours after dosing. If methotrexate is administered in combination chemotherapy regimens, the dosage should be reduced, taking into consideration any overlapping toxicity of the other drug components.
Dosage for Psoriasis and Rheumatoid arthritis: The prescriber should specify the day of intake on the prescription.
Psoriasis: Before starting treatment it is advisable to give the patient a test dose of 2.5-5.0 mg to exclude unexpected toxic effects. If, one week later, appropriate laboratory tests are normal, treatment may be initiated.
The usual dose is 7.5 - 15 mg once a week. For the treatment of severe psoriasis, the total weekly dosage can be raised to 20 - 25 mg administered orally as necessary. Dosage should be adjusted according to the patient's response and the haematological toxicity.
Rheumatoid Arthritis: In adults with severe, active, classical or definite rheumatoid arthritis who are unresponsive or intolerant to conventional therapy, methotrexate tablet should be taken as 7.5-15 mg once a week. The total weekly dosage can be raised to 20-25 mg as necessary. Dosage should be adjusted according to the patient's response and the haematological toxicity.
Dosage for Polyarticular Juvenile Idiopathic Arthritis: The recommended starting dosage of methotrexate tablet is 10 mg/m² orally once weekly with escalation to achieve optimal response. Dosages of more than 30 mg/m² once weekly result in an increased risk of serious adverse reactions, including myelosuppression. When responses are observed, the majority occurred between 3 and 6 weeks from initiation of treatment; however, responses have occurred up to 12 weeks after treatment initiation.
Paediatric population: Treatment should follow currently valid protocols for children. Safety and effectiveness in children have not been established, other than in cancer chemotherapy and polyarticular juvenile idiopathic arthritis. In clinical trail experience, the most common adverse reactions reported in patients 2 to 18 years of age with pJIA treated with methotrexate 5 mg/m² to 20 mg/m² orally once weekly or 0.1 to 0.65 mg/kg orally once weekly were as follows: elevated liver tests 14%; gastrointestinal reactions (e.g., nausea, vomiting, diarrhea) 11%; stomatitis 2%; leukopenia 2%; headache 1.2%; alopecia 0.5%; dizziness 0.2%; rash 0.2%. Most patients received concomitant NSAIDs and some also received corticosteroids.
Use in Elderly: Methotrexate should be used with extreme caution in elderly patients. A reduction in dosage should be considered due to reduced liver and kidney function as well as lower folate reserves, which occur with increased age.
Use in patients with renal impairment - dose adjustments: Methotrexate is excreted to a significant extent by the kidneys, and therefore should be used with caution in patients with impaired renal function (see Contraindications and Precautions). The health care provider may need to adjust the dose to prevent accumulation of drug. The table as follows provided recommended starting doses in renally impaired patients; dosing may need further adjustment due to wide intersubject pK variability. (See table.)

Click on icon to see table/diagram/image

Patients with hepatic impairment: Methotrexate should be administered with great caution, if at all, to patients with significant current or previous liver disease, especially if due to alcohol (see Contraindications and Precautions).
Use in a patient with a third distribution space (pleural effusions, ascites): As the half-life of methotrexate can be prolonged to 4 times the normal length in patients who possess a third distribution space dose reduction or, in some cases, discontinuation of methotrexate administration may be required.
Special note: If changing the oral application to parenteral administration a reduction of the dose may be required due to the variable bioavailability of methotrexate after oral administration.
Method of Administration: Oral.