Xatmep (Page 4 of 5)

8.2 Lactation

Risk Summary

Limited published literature report the presence of methotrexate in human milk in low amounts. The highest breast milk to plasma concentration ratio demonstrated was 0.08:1. No information is available on the effects of methotrexate on a breastfed infant or on milk production. Because of the potential for serious adverse reactions, including myelosuppression, from methotrexate in breastfed infants, advise women not to breastfeed during XATMEP therapy.

8.3 Females and Males of Reproductive Potential

Pregnancy Testing

Test for pregnancy prior to initiating therapy with XATMEP.

Contraception

Females

XATMEP can cause fetal harm when administered to a pregnant woman [see Use in Specific Populations (8.1)].

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

Males

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

Infertility

Females

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

Males

Based on published reports of male infertility after therapy with methotrexate, advise males of reproductive potential that XATMEP can cause oligospermia or infertility during and after cessation of therapy. It is not known if the infertility may be reversed in all affected males.

8.4 Pediatric Use

Safety and effectiveness of XATMEP in pediatric patients have been established for the treatment of pediatric patients with acute lymphoblastic leukemia (ALL) as part of a multi-phase, combination chemotherapy maintenance regimen and for the management of pediatric patients with active polyarticular juvenile idiopathic arthritis (pJIA) [see Clinical Studies (14)].

8.6 Renal Impairment

Methotrexate elimination is reduced in patients with impaired renal function. Monitor patients with renal impairment for an extended period of time. Consider a dose reduction or, in some cases, discontinue XATMEP administration [see Warnings and Precautions (5.3)].

8.7 Hepatic Impairment

The effect of hepatic impairment on methotrexate pharmacokinetics has not been studied. Patients with hepatic impairment may be more susceptible to hepatotoxicity [see Warnings and Precautions (5.5)]. Consider dose adjustments or alternative treatments in patients with baseline hepatic impairment.

10 OVERDOSAGE

Manifestations

Fatal overdosage has occurred with methotrexate. Manifestations of overdosage include adverse reactions reported at pharmacologic doses, particularly hematologic and gastrointestinal reactions (e.g., leukopenia, thrombocytopenia, anemia, pancytopenia, bone marrow suppression, mucositis, stomatitis, oral ulceration, nausea, vomiting, gastrointestinal ulceration, or gastrointestinal bleeding). In some cases, no symptoms were reported.

Management

Leucovorin and levoleucovorin are indicated to diminish the toxicity and counteract the effect of inadvertently administered overdosages of methotrexate. Administer leucovorin or levoleucovorin as soon as possible after overdosage (refer to the leucovorin or levoleucovorin Prescribing Information). Monitor serum methotrexate concentrations closely to guide leucovorin or levoleucovorin therapy. Monitor serum creatinine concentrations closely because high serum methotrexate concentrations may cause renal damage leading to acute renal failure.

Glucarpidase is indicated for the treatment of toxic methotrexate concentrations in patients with delayed methotrexate clearance due to impaired renal function (refer to the glucarpidase Prescribing Information). If glucarpidase is used, do not administer leucovorin within 2 hours before or after a dose of glucarpidase because leucovorin is a substrate for glucarpidase.

In cases of massive overdosage, hydration and urinary alkalinization may be necessary to prevent the precipitation of methotrexate and/or its metabolites in the renal tubules. Neither hemodialysis nor peritoneal dialysis has been shown to improve methotrexate elimination. However, effective clearance of methotrexate has been reported with acute, intermittent hemodialysis using a high-flux dialyzer.

11 DESCRIPTION

XATMEP contains methotrexate, a folate analog metabolic inhibitor.

Chemically methotrexate is N-[4-[[(2,4-diamino-6-pteridinyl)methyl]methylamino]-benzoyl]-L-glutamic acid. The structural formula is:

Structural Formula
(click image for full-size original)

XATMEP is a clear yellow to orange oral solution that contains 2.5 mg of methotrexate per milliliter (equivalent to 2.74 mg of methotrexate sodium/mL). Inactive ingredients include purified water, sodium citrate, citric acid, methylparaben sodium, propylparaben sodium, and sucralose. It may also contain sodium hydroxide or hydrochloric acid for pH adjustment.

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 pJIA is unknown; it may affect immune function.

12.2 Pharmacodynamics

Two reports describe in vitro methotrexate inhibition of DNA precursor uptake by stimulated mono-nuclear cells, and another describes in animal polyarthritis partial correction by methotrexate of spleen cell hyporesponsiveness and suppressed IL 2 production. Other laboratories, however, have been unable to demonstrate similar effects.

12.3 Pharmacokinetics

Absorption

In pediatric patients with ALL, oral absorption of methotrexate appears to be dose dependent; the absorption of doses greater than 40 mg/m2 is significantly less than that of lower doses. The extent of oral absorption ranges from 23% to 95%, and the time to peak concentration (Tmax ) ranges from 0.7 hours to 4 hours after an oral dose of 15 mg/m2.

In pediatric patients with pJIA, mean serum concentrations were 0.59 micromolar (range, 0.03 to 1.40) at 1 hour, 0.44 micromolar (range, 0.01 to 1.00) at 2 hours, and 0.29 micromolar (range 0.06 to 0.58) at 3 hours following oral administration of methotrexate at a dose of 6.4 mg/m2 /week to 11.2 mg/m2 /week.

Effect of Food

The administration of XATMEP with food did not affect the area under the curve (AUC), but decreased the maximal concentrations (Cmax ) by 50% and delayed the absorption.

Distribution

After intravenous administration, the initial volume of distribution is approximately 0.18 L/kg (18% of body weight) and steady-state volume of distribution is approximately 0.4 to 0.8 L/kg (40% to 80% of body weight).

Methotrexate competes with reduced folates for active transport across cell membranes by means of a single carrier-mediated active transport process. At serum concentrations greater than 100 micromolar, passive diffusion becomes a major pathway by which effective intracellular concentrations can be achieved.

Methotrexate in serum is approximately 50% protein bound.

Methotrexate does not penetrate the blood-cerebrospinal fluid barrier in therapeutic amounts when given orally.

Elimination

In adults, the half-life of methotrexate following administration of low dose methotrexate (less than 30 mg/m2) ranges from 3 hours to 10 hours.

In pediatric patients receiving methotrexate for ALL (6.3 mg/m2 to 30 mg/m2), the terminal half-life has been reported to range from 0.7 hours to 5.8 hours.

In pediatric patients receiving methotrexate for JIA (3.75 mg/m2 to 26.2 mg/m2), the terminal half-life has been reported to range from 0.9 hours to 2.3 hours.

Metabolism

Methotrexate undergoes hepatic and intracellular metabolism to polyglutamated forms which can be converted back to methotrexate by hydrolase enzymes. These polyglutamates act as inhibitors of dihydrofolate reductase and thymidylate synthetase. Small amounts of methotrexate polyglutamates may remain in tissues for extended periods. The retention and prolonged drug action of these active metabolites vary among different cells, tissues and tumors. A small amount of metabolism to 7‑hydroxymethotrexate may occur at doses commonly prescribed. The aqueous solubility of 7‑hydroxymethotrexate is 3- to 5-fold lower than the parent compound. Methotrexate is partially metabolized by intestinal flora after oral administration.

Excretion

Renal excretion is the primary route of elimination and is dependent upon dosage and route of administration. With IV administration, 80% to 90% of the administered dose is excreted unchanged in the urine within 24 hours. There is limited biliary excretion amounting to 10% or less of the administered dose. Enterohepatic recirculation of methotrexate has been proposed.

Renal excretion occurs by glomerular filtration and active tubular secretion. Nonlinear elimination due to saturation of renal tubular reabsorption has been observed in patients at doses between 7.5 mg and 30 mg. Impaired renal function, as well as concurrent use of drugs such as weak organic acids that also undergo tubular secretion, can markedly increase methotrexate serum levels.

Methotrexate clearance decreases at higher doses. Delayed drug clearance has been identified as one of the major factors responsible for methotrexate toxicity. When a patient has delayed drug elimination due to compromised renal function, a third-space effusion, or other causes, methotrexate serum concentrations may remain elevated for prolonged periods.

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