Đăng xuất
Important warning concerning the dosing of methotrexate: See Warnings.
Rheumatoid arthritis: The usual dose is 7.5-15 mg once weekly. The dose may be adjusted gradually to achieve an optimal response but should not exceed a total weekly dose of 25 mg. Doses exceeding 20 mg per week can be associated with a significant increase in toxicity, especially bone marrow suppression. Thereafter the dose should be reduced to the lowest possible effective dose which in most cases is achieved within 6 weeks.
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 taken once weekly. As necessary, the total weekly dose can be increased up to 25 mg. Doses exceeding 20 mg per week can be associated with a significant increase in toxicity, especially bone marrow suppression. Thereafter the dose should be reduced to the lowest effective dose according to therapeutic response which in most cases is achieved within 4 to 8 weeks.
The patient should be fully informed of the risks involved and the clinician should pay particular attention to the appearance of liver toxicity by carrying out liver function tests before starting methotrexate treatment, and repeating these during therapy. The aim of therapy should be to reduce the dose to the lowest possible level with the longest possible rest period. The use of methotrexate may permit the return to conventional topical therapy.
Cytostatic: Dosage in acute lymphoblastic leukemia: Low-dose methotrexate is used in the maintenance treatment of acute lymphoblastic leukemia in children aged 3 years and over, adolescents and adults within complex protocols in combination with other cytostatic medicinal products. Treatment should follow current therapy protocols.
Common accepted single doses lie in the range of 20-40 mg/m2 body surface area and are usually given once weekly.
If methotrexate is administered in combination with chemotherapy regimens, the dosage should take into consideration any overlapping toxicity of the other medicinal product components.
Higher dosages should be given parenterally.
Pediatric population: Methotrexate should be used with caution in pediatric patients. Treatment should follow currently valid therapy protocols for children.
Doses are usually based on the patient's body surface area and maintenance treatment represents a long-term treatment.
The use in children below 3 years of age is not recommended as insufficient data on efficacy and safety are available for this population.
Special populations: Use in elderly patients: Methotrexate should be used with extreme caution in elderly patients, a dose reduction should be considered due to reduced liver and kidney function as well as lower folate reserves which occur with increased age.
Patients with renal impairment: Methotrexate should be used with caution in patients with impaired renal function. The dose should be adjusted as follows: Dosage recommendations (see Table 1).
Click on icon to see table/diagram/imagePatients 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. Methotrexate is contraindicated in patients with significantly impaired hepatic function.
Use in patients 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.
Folic acid or folinic acid supplementation may be considered according to current treatment guidelines.
