DOSES LARGER THAN 100 MG ARE USUALLY GIVEN PARTLY OR WHOLLY BY INTRAVENOUS INFUSION OVER NOT MORE THAN 24 HOURS.
ACUTE LYMPHOBLASTIC LEUKAEMIA : MAINTENANCE THERAPY:15 MG/M2 ONCE OR TWICE WEEKLY, BY MOUTH OR INTRAMUSCULARLY, WITH OTHER AGENTS SUCH AS MERCAPTOPURINE; 20 TO 30 MG/M2 TWICE WEEKLY HAS ALSO BEEN GIVEN. ALTERNATIVELY, 2.5 MG/KG MAY BE GIVEN INTRAVENOUSLY EVERY 14 DAYS.
MENINGEAL LEUKAEMIA : INTRATHECAL INJECTION OF 12 MG/M2 (MAXIMUM 15 MG) ONCE WEEKLY FOR 2 TO 3 WEEKS, THEN ONCE MONTHLY; AN ALTERNATIVE IS 200 TO 500 MICROGRAMS/KG AT INTERVALS OF 2 TO 5 DAYS UNTIL THE CELL COUNT OF THE CSF RETURNS TO NORMAL. ANOTHER REGIMEN HAS BEEN RECOMMENDED FOR CHILDREN BASED ON AGE, WITH CHILDREN UNDER THE AGE OF 1 YEAR RECEIVING 6 MG, 8 MG FOR THOSE 1 YEAR OF AGE, 10 MG IN 2-YEAR-OLDS, AND 12 MG IN THOSE 3 YEARS OF AGE OR OLDER. INTRATHECAL DOSES HAVE ALSO SOMETIMES BEEN GIVEN PROPHYLACTICALLY TO PATIENTS WITH LYMPHOBLASTIC LEUKAEMIA IN ASSOCIATION WITH INTRATHECAL CYTARABINE AND HYDROCORTISONE. METHOTREXATE IN INTRAVENOUS DOSES OF ABOUT 500 MG/M2, FOLLOWED BY FOLINIC ACID RESCUE, MAY ALSO PRODUCE EFFECTIVE CONCENTRATIONS IN THE CSF AND HAS BEEN USED FOR MENINGEAL LEUKAEMIA.
CHORIOCARCINOMA: DOSES OF 15 TO 30 MG DAILY BY MOUTH OR INTRAMUSCULARLY FOR 5 DAYS REPEATED AFTER AN INTERVAL OF 1 WEEK OR MORE, FOR 3 TO 5 COURSES. ALTERNATIVELY 0.25 TO 1 MG/KG UP TO A MAXIMUM OF 60 MG HAS BEEN GIVEN INTRAMUSCULARLY EVERY 48 HOURS FOR 4 DOSES, FOLLOWED BY FOLINIC ACID RESCUE, AND REPEATED AT INTERVALS OF 7 DAYS FOR 4 OR MORE COURSES. COMBINATION CHEMOTHERAPY MAY BE NECESSARY IN PATIENTS WITH METASTASES.
BREAST CANCER: DOSES OF 10 TO 60 MG/M2 ARE GIVEN IV, OFTEN WITH CYCLOPHOSPHAMIDE AND FLUOROURACIL.
LYMPHOSARCOMA : DOSES OF 0.625 TO 2.5 MG/KG DAILY HAVE BEEN SUGGESTED WITH OTHER ANTINEOPLASTICS. ALTERNATIVELY, HIGHER DOSES OF UP TO 30 MG/KG HAVE BEEN GIVEN INTRAVENOUSLY, FOLLOWED BY FOLINIC ACID RESCUE.
BURKITT'S LYMPHOMA : 10 TO 25 MG OF METHOTREXATE HAS BEEN GIVEN DAILY BY MOUTH FOR 4 TO 8 DAYS, REPEATED AFTER AN INTERVAL OF 7 TO 10 DAYS.
MYCOSIS FUNGOIDES : MAY BE GIVEN 2.5 TO 10 MG DAILY BY MOUTH TO INDUCE REMISSION; ALTERNATIVELY 50 MG MAY BE GIVEN WEEKLY AS A SINGLE DOSE OR TWO DIVIDED DOSES, BY INTRAMUSCULAR INJECTION.
OSTEOSARCOMA: VERY HIGH DOSES, IN THE RANGE 12 TO 15 G/M2 HAVE BEEN GIVEN BY INTRAVENOUS INFUSION, FOLLOWED BY FOLINIC ACID, AS PART OF COMBINED ADJUVANT THERAPY IN PATIENTS WITH. HIGH-DOSE REGIMENS HAVE BEEN TRIED IN OTHER MALIGNANCIES, INCLUDING CARCINOMA OF THE LUNG AND OF THE HEAD AND NECK.
PSORIASIS : SINGLE WEEKLY DOSES OF 10 TO 25 MG MAY BE GIVEN BY MOUTH OR BY INTRAMUSCULAR OR INTRAVENOUS INJECTION IN THE TREATMENT OF PSORIASIS AND ADJUSTED BY RESPONSE.
RHEUMATOID ARTHRITIS : DOSES OF 7.5 MG BY MOUTH ONCE WEEKLY ARE USED, ADJUSTED BY RESPONSE AND NOT EXCEEDING 20 MG/WEEK.
SLE : GIVEN ONCE WEEKLY IN LOW TO MODERATE DOSES OF METHOTREXATE SIGNIFICANTLY DECREASED DISEASE ACTIVITY.
ECTOPIC PREGNANCY : MANAGEMENT WITH INTRAMUSCULAR METHOTREXATE MAY BE APPROPRIATE FOR SELECTED WOMEN WITH SMALL UNRUPTURED TUBAL PREGNANCIES WHO ARE HAEMODYNAMICALLY STABLE, HAVE LOW SERUM-CHORIONIC GONADOTROPHIN CONCENTRATIONS, AND LACK CONTRA-INDICATIONS TO METHOTREXATE USE. SURGERY IS PREFERRED WHERE THERE IS CARDIAC ACTIVITY IN THE CONCEPTUS, SINCE A LIVING EMBRYO INCREASES RESISTANCE TO METHOTREXATE. TWO REGIMENS OF INTRAMUSCULAR METHOTREXATE HAVE BEEN DESCRIBED. A MULTIPLE-DOSE REGIMEN OF 1 MG/KG ON 4 ALTERNATE DAYS, WITH FOLINIC ACID RESCUE, HAS SIMILAR EFFICACY TO SURGERY. A SINGLE DOSE OF 50 MG/M2 CAN BE USED INSTEAD BUT SYSTEMATIC REVIEWS HAVE INDICATED THAT IT HAS A HIGHER FAILURE RATE THAN SURGERY AND ABOUT 20% OF PATIENTS WILL REQUIRE MORE THAN ONE CYCLE OF TREATMENT. THE ADDITION OF AN ORAL DOSE OF MIFEPRISTONE TO SINGLE-DOSE METHOTREXATE HAS BEEN INVESTIGATED AND MAY REDUCE TREATMENT FAILURE RATES.
CHROHN'S DISEASE : METHOTREXATE GIVEN INTRAMUSCULARLY ONCE WEEKLY IN A DOSE OF 25 MG)
MULTIPLE SCLEROSIS : 7.5 MG BY MOUTH WEEKLY MAY BE OF BENEFIT IN SLOWING THE PROGRESSION OF MULTIPLE SCLEROSIS