Methotrexate (Page 5 of 8)

8.2 Lactation

Risk Summary

Limited published literature report the presence of methotrexate in human milk in low amounts, with the highest breast milk to plasma concentration ratio reported to be 0.08:1. There are no data on the effects of methotrexate or its metabolites on the breastfed child or their effects on milk production. Because of the potential for serious adverse reactions in a breastfed child, instruct women not to breastfeed during treatment with methotrexate tablets and for 1 week after the final dose.

8.3 Females and Males of Reproductive Potential

Methotrexate can cause malformations and fetal death at doses less than or equal to the recommended clinical doses [see Use in Specific Populations (8.1)].

Pregnancy Testing

Verify the pregnancy status of females of reproductive potential prior to initiating methotrexate tablets [see Contraindications (4), Use in Specific Populations (8.1)].

Contraception

Females

Advise females of reproductive potential to use effective contraception during treatment with methotrexate tablets and for 6 months after the final dose.

Males

Methotrexate can cause chromosomal damage to sperm cells. Advise males with female partners of reproductive potential to use effective contraception during treatment with methotrexate tablets and for 3 months after the final dose.

Infertility

Females

Based on published reports of female infertility after methotrexate, advise females of reproductive potential that methotrexate can cause impairment of fertility and menstrual dysfunction during treatment with methotrexate tablets and after the final dose. It is not known if the infertility may be reversed in all affected females.

Males

Based on published reports of male infertility after methotrexate, advise males that methotrexate can cause oligospermia or infertility during treatment with methotrexate tablets and after the final dose. It is not known if the infertility may be reversed in all affected males.

8.4 Pediatric Use

The safety and effectiveness of methotrexate tablets in pediatric patients have been established for the treatment of ALL as part of the combination chemotherapy maintenance regimen and the treatment of pJIA [see Indications and Usage (1), Dosage and Administration (2)]. No new safety signals have been observed in pediatric patients in clinical studies [see Adverse Reactions (6.1)].

The safety and effectiveness of methotrexate tablets have not been established in pediatric patients for the other indications [see Indications and Usage (1)].

8.5 Geriatric Use

Clinical studies of methotrexate did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.

8.6 Renal Impairment

Methotrexate elimination is reduced in patients with renal impairment [see Clinical Pharmacology (12.3)]. Patients with renal impairment are at increased risk for methotrexate adverse reactions. Closely monitor patients with renal impairment [creatinine clearance (CLcr) less than 90 mL/min, Cockcroft-Gault] for adverse reactions. Reduce the dosage or discontinue methotrexate tablets as appropriate [see Warnings and Precautions (5.8)].

8.7 Hepatic Impairment

The pharmacokinetics and safety of methotrexate in patients with hepatic impairment is unknown. Patients with hepatic impairment may be at increased risk for methotrexate adverse reactions based on the elimination characteristics of methotrexate [see Clinical Pharmacology (12.3)]. Closely monitor patients with hepatic impairment for adverse reactions. Reduce the dosage or discontinue methotrexate tablets as appropriate [see Warnings and Precautions (5.5)] .

10 OVERDOSAGE

Overdosage, including fatal overdosage, has occurred with methotrexate [see Warnings and Precautions (5.9)].

Manifestations: Manifestations of methotrexate overdosage include adverse reactions reported at pharmacologic doses, particularly hematologic and gastrointestinal reactions (e.g., leukopenia, thrombocytopenia, anemia, pancytopenia, myelosuppression, mucositis, stomatitis, oral ulceration, nausea, vomiting, gastrointestinal ulceration, or gastrointestinal bleeding). In some cases, no symptoms were reported; however, sepsis or septic shock, renal failure, and aplastic anemia were also reported.

Management: Leucovorin and levoleucovorin are indicated for diminishing the methotrexate adverse reactions of methotrexate overdosage. Administer leucovorin or levoleucovorin as soon as possible after methotrexate overdosage). Monitor serum creatinine and methotrexate levels to guide leucovorin or levoleucovorin therapy. Refer to the leucovorin or levoleucovorin prescribing information for additional dosage information.

Glucarpidase is indicated for the treatment of toxic plasma methotrexate concentrations (> 1 micromole per liter) in patients with delayed methotrexate clearance due to impaired renal function. Refer to the glucarpidase prescribing information for additional dosage information.

Administer concomitant hydration and urinary alkalinization.

Neither hemodialysis nor peritoneal dialysis has been shown to improve methotrexate elimination; however, methotrexate has been effectively cleared with acute, intermittent hemodialysis using a high-flux dialyzer.

11 DESCRIPTION

Methotrexate is dihydrofolate reductase inhibitor with the chemical name of N-[4-[[(2,4 diamino-6-pteridinyl) methyl]methylamino]benzoyl]-L glutamic acid. The molecular formula is C 20 H 22 N 8 O 5 and the molecular weight is 454.4 g/mol. The structural formula is:

Methotrexate Structural Formula
(click image for full-size original)

Methotrexate Tablets, USP for oral use are available in bottles of 100 tablets. Each methotrexate tablet contains 2.5 mg methotrexate equivalent to 2.74 mg methotrexate sodium and the following inactive ingredients: colloidal silicon dioxide, FD&C Red No. 40 Aluminum Lake, lactose monohydrate, magnesium stearate, microcrystalline cellulose, pregelatinized starch (corn), sodium carbonate (monohydrate), sodium lauryl sulfate and sodium starch glycolate (potato).

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Methotrexate inhibits dihydrofolic acid reductase. Dihydrofolates must be reduced to tetrahydrofolates by this enzyme before they can be utilized as carriers of one-carbon groups in the synthesis of purine nucleotides and thymidylate. Therefore, methotrexate interferes with DNA synthesis, repair, and cellular replication. Actively proliferating tissues such as malignant cells, bone marrow, fetal cells, buccal and intestinal mucosa, and cells of the urinary bladder are in general more sensitive to this effect of methotrexate.

The mechanism of action in rheumatoid arthritis and in psoriasis is unknown.

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