2 Recommended Dose and Dosage Adjustment Impaired methotrexate Elimination or Accidental Overdosage: LEDERLE LEUCOVORIN rescue should begin as soon as possible after an inadvertent overdosage and within 24 hours of methotrexate administration when there is delayed excretion (see 7 WARNINGS AND PRECAUTIONS).
As the time interval between the administration of antifolate and LEDERLE LEUCOVORIN rescue increases, the effectiveness of LEDERLE LEUCOVORIN in counteracting toxicity decreases. There are no fixed guidelines regarding the dose of methotrexate that triggers an automatic subsequent calcium folinate administration, since tolerance to this folate antagonist depends on various factors.
The dose of methotrexate varies, nevertheless folinate rescue is necessary when methotrexate is given at doses exceeding 500 mg/m2 and has to be considered with doses of 100 mg - 500 mg/m2. Calcium folinate rescue treatment should commence approximately 24 hours after the beginning of methotrexate infusion.
Dosage regimens vary depending upon the dose of methotrexate administered. In general, calcium folinate should be administered at a dose of 15 mg (approximately 10 mg/m2) every 6 hours for 10 doses, either parenterally by intramuscular injection, bolus intravenous injection, intravenous infusion, or orally using calcium folinate tablets.
Monitoring of the serum methotrexate (MTX) concentration is essential in determining the optimal dose and duration of therapy. If serum creatinine increases after methotrexate therapy or if methotrexate plasma concentrations are above certain threshold (see Table 1), the dose of calcium folinate should be increased according to the plasma methotrexate concentrations as soon as the risk is recognized.
In the presence of gastrointestinal toxicity, nausea, or vomiting, calcium folinate should be administered parenterally. In the case of intravenous administration, no more than 160 mg of calcium folinate should be injected per minute due to the calcium content of the solution.
Further, oral administration of doses greater than 25 mg is not recommended since the digestive absorption of calcium folinate is saturable; these doses should be administered parenterally. In addition to calcium folinate administration, measures to ensure the prompt excretion of methotrexate are an integral part of the calcium folinate rescue treatment.
These measures include: a) Maintenance of urine output above 2,500 mL/24 hr in adults by increased oral or intravenous fluids 12 hours before and for 36 hours after the end of methotrexate infusion. 0 before methotrexate infusion. Foods, drinks and drugs that may increase urinary acidity should be avoided during the therapy.
c) Plasma methotrexate concentration and serum creatinine should be measured at least 24, 48, and 72 hours after the initiation of the methotrexate infusion. These measurements must be continued until the plasma methotrexate level is less than 5 x 10-8 molar.
05 μm). LEDERLE LEUCO VORIN (calcium folinate) – Product Monograph Page 6 of 21 Delayed methotrexate excretion may be seen in some patients. This may be caused by a third space accumulation (as seen in ascites or pleural effusion for example), renal insufficiency or inadequate hydration (see 7 WARNINGS AND PRECAUTIONS).
Under such circumstances, higher doses of calcium folinate and/or prolonged administration may be indicated. Some dosage and administration guidelines are given in Table 1. 1 μM at 72 hours. 15 mg PO, IM, or IV every 6 hours for 60 hours (10 doses starting at 24 hours after start of methotrexate infusion).
1 μM at 96 hours after administration. 1 μM. Delayed early methotrexate elimination and/or evidence of acute renal failure Serum methotrexate level of > 10 μM at 24 hours, or > 1 μM at 48 hours after administration OR a 100% or greater increase in serum creatinine level at 24 hours after methotrexate administration.
1 μM. Hydration (3 L/d) and urinary alkalinization with NaHC03 should be employed concomitantly. 0 or greater.
Megaloblastic Anemia Due to Folic Acid Deficiency:
Doses up to 15 mg daily have been suggested. Health Canada has not authorized an indication for pediatric use. 4 Administration Tablets are administered orally. LEDERLE LEUCO VORIN (calcium folinate) – Product Monograph Page 7 of 21