Methotrexate

Treatment of cancer and rheumatoid arthritis

Methotrexate is a drug used for the treatment of cancer, also known as cytotoxic drugs. In order to reduce its cytotoxicity, it can be used in conjunction with calcium leucovorin. It is primarily used for the treatment of acute leukemia (acute lymphocytic leukemia), breast cancer, malignant mole and choriocarcinoma, head and neck cancer, bone cancer, leukemia, spinal cord meningeal infiltration, lung cancer, reproductive system cancer, liver cancer, refractory psoriasis vulgaris, dermatomyositis, body myositis, ankylosing spondylitis inflammation, Crohn's disease, psoriasis and psoriatic arthritis, Behcet's disease and autoimmune disease. In Rheumatic Arthritis:
Methotrexate is an immunosuppressant and can be used for easing the process of rheumatism with a particularly excellent efficacy in treating synovial inflammation of rheumatoid arthritis and is the most frequently used drugs for treating rheumatoid diseases.

• Methotrexate (MTX), is one of first line DMARDs(disease-modifying antirheumatic drugs).The order of agent selection is not clearly defined, but MTX is often chosen initially because long-term data suggest superior outcomes compared with other DMARDs and lower cost than biologic agents.
• MTX inhibits cytokine production and purine biosynthesis, which may be responsible for its antiinflammatory properties. Its onset is relatively rapid (as early as 2 to 3 weeks), and 45% to 67% of patients remained on it in studies ranging from 5 to 7 years.
• Toxicities are GI (stomatitis, diarrhea, nausea, vomiting), hematologic (thrombocytopenia, leukopenia), pulmonary (fibrosis, pneumonitis), and hepatic (elevated enzymes, rare cirrhosis). MTX is contraindicated in pregnant and nursing women, chronic liver disease, immunodeficiency, pleural or peritoneal effusions, leukopenia, thrombocytopenia, preexisting blood disorders, and creatinine clearance <40 mL/min.

History of discovery

Methotrexate is the first effective anti-metabolites for treatment of tumor with good efficacy in treating choriocarcinoma and acute lymphoblastic leukemia. In 1940s, the scientists discovered that the active ingredient of Lactobacillus casei in inhibiting mice tumor-transplanted sarcoma S180 and spontaneous breast cancer is pterin tri-glutamic acid with the later one having a weak anti-folate effect. It has also observed of bone marrow suppression upon lack of folic acid. Folic acid can promote the development of leukemia. Therefore, people initially tried to identify anti-cancer drugs from folate antimetabolites. In 1947, aminopterin had been subject to clinical trials and found to be effective in treating childhood leukemia. Then it was found of that methotrexate has high therapeutic index in treating the mouse leukemia L1210. In 1950s, it had been applied to the clinical trial and had quickly substituted the aminopterin for the treatment of leukemia and had been later further expanded for treating other tumors. It has been one of the most intensively studied anticancer drugs.
In the field of rheumatoid, though in 1951, Gubner had successfully applied aminopterin for the methotrexate treatment of rheumatoid arthritis and psoriasis. However, at the time, methotrexate was still considered as the anti-metabolic anti-cancer drugs, therefore, it is natural that people think it has a really high toxicity. Another reason is the emergence of hormones, resulting in almost all the attention being focused on hormone therapy. Only a few researchers in the field of rheumatology include Rex Hoffmeister et al had began to apply a small dose of methotrexate for treatment of autoimmune diseases.
The above information is edited by the Chemicalbook of Dai Xiongfeng.

Immunosuppressants

Methotrexate is an anti-folate anti-metabolite with a strong immunosuppressive effect. It is first anti-folate agents that have been successfully applied to clinical field. It is effective for not only treating leukemia but also for treating solid tumors and is a kind of basic clinical anti-tumor drugs. Methotrexate can selectively act on the proliferation of cells, preventing cell division and proliferation of immune mother cells. It has inhibitory effect against humoral and cellular immunity and also has strong anti-inflammatory effect. It has inhibitory effect on the primary immune response and secondary immune response, delayed hypersensitivity and graft-versus-host reaction. Applying medication at the same time of antigen-stimulation or after one to two days can yield the strongest immunosuppressive medication with being invalid prior to antigen stimulation. Clinically it is mainly used in treatment of autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus and dermatomyositis. In addition, methotrexate is also effective for treating acute leukemia, choriocarcinoma, osteosarcoma, breast cancer, and testicular cancer and so on. It is a commonly used cycle specific drugs in combination chemotherapy.

Pharmacological effects

Methotrexate is an antifolate antineoplastic drug with inhibitory effect on a variety of animal tumor. Experiments have shown that this drug work through competitive inhibition on the dihydrofolate reductase. Dihydrofolate reductase is a key enzyme in DNA synthesis, and in particular being indispensable in the process of conversion of folate to tetrahydrofolate and deoxyuridine methylation into thymidine. This drug can selectively act on the DNA synthesis period (i.e. S phase), belonging to a cycle specific drugs. Recently it has been considered that the product has a second point of action, namely G1/S transition period; it can also inhibit IL-2 synthesis and neutrophil chemotaxis, therefore having immunosuppressive and anti-inflammatory effects. Upon large doses, it can further have direct toxicity on non-proliferating cells especially liver cells. It is clinically commonly used in as an antidote.
Methotrexate (MTX for short) has a similar structure as folic. The 4’ hydroxy and 10’ hydrogen in NH respectively correspond to the NH3 group and CH3 in the MTX. MTX can bind with the dihydrofolate reductase, blocking the reduction of folate and dihydrofolate into activated form of tetrahydrofolate, thereby inhibiting the intracellular one-carbon transfer, and affecting the newly synthesized purine nucleotide and conversion of deoxyuridine to deoxythymidine nucleotides, further blocking the DNA and RNA synthesis. The plasma concentration of MTX is 10-8mol/L, and can effectively block the incorporation of deoxyuridine into DNA via deoxythymidine nucleotide with the inhibitory concentration of purine synthesis being 10-7mol/L. The combination of MTX with dihydrofolate reductase is reversible but very strong. In order to fight against the binding of MTX, dihydrofolate should have an at least 1000 fold as high as MTX. In vitro, when MTX is less than the concentration of complete inhibition of DNA synthesis, it can induce the differentiation of human choriocarcinoma cell, increasing the generation of human chorionic gonadotropin. MTX is a cell cycle-specific drug with its major effect acting on S-phase cell with specific effect on the G1 phase as well and having delayed effect on the G1/S.

Pharmacokinetics

This product has an excellent oral absorption with the plasma concentration reaching peak after 30~60min. Large-dose administration or simultaneous administration without food yield a poor absorption. After intramuscular injection, the blood concentration can be maintained for a longer period with drug disappearing slowly after intrathecal injection, the cerebrospinal fluid concentration can be maintained for about 6d. This product, after absorption, has 60% to 85% for binding with plasma protein. Simultaneously taking aspirin or sulfa drugs can lead to high blood concentration of this product with consequent increase in both efficacy and toxicity. Poor kidney function may also increase the toxicity of this product. A small amount of this product can be able to penetrate through the blood-brain barrier. This drug is mainly distributed in the liver, kidney with also a fraction existing in the main bone marrow. Drug has plasma half-life of 2h. Drug is primarily excreted in the prototype by the urine with the urine excretion amount being 90% within 48h while excretion amount of biliary and fecal being minimal.

Clinical application

It is effective in treating acute leukemia with better efficacy in pediatric patients. It has a good efficacy in treating choriocarcinoma and malignant mole. Large dose administration is effective in treating osteosarcoma, soft tissue sarcoma, lung cancer, testicular cancer, breast cancer, and ovarian cancer. It is also effective in treating head and neck cancer, liver cancer and gastrointestinal cancer. Arterial infusion of this product has goo efficacy in treating head and neck cancer and liver cancer. However, it is rarely used for treating psoriasis and psoriasis.

Dosage

1, early treatment of leukemia usually applies multiple dose of treatment; adult oral 2.5~10 mg/d with total amount of 50~150 mg. Children: 1.25~5mg/d, tend to apply large-scale intermittent dosing regimen, administered therapy, oral administration or intramuscular injection 2 times per week with 0.25~0.75 mg/kg at each time; adults usually take 20~25 mg per time; sheath injection of 10~15 mg/time; children: 6~12mg/times according to the ages; for therapeutic use once a day and continue for 3 d; for prevention, apply once every 4-8 weeks.
2, Choriocarcinoma, adult: 10~30mg; use intramuscular injection or oral administration once daily for continuous 5d. You can repeat the treatment course according to the reaction of the patient.
3, solid cancer, preferably for continuous arterial infusion while giving intermittent intramuscular injection of leucovorin (CF); the usual dose is 25~50mg/d, CF6~9mg, apply intramuscular injection once every 4~6h.
4, apply large-dose for treating osteosarcoma and combine with CF detoxification. The general dose of this product is generally 3~20g/m2. It can be dissolved in 500~1000 mL of 5% glucose injection for intravenous infusion of 4h. After dropping of 2~6h, you can begin to use CF with a dose of 6~12mg for intramuscular injection (or oral) once each 6h for a total of 3 d. In order to ensure that the drug can be rapidly excreted from the body, we should replenish electrolytes, water and sodium bicarbonate at I d before or every 1~2d during the infusion to make the daily urine output be over 3000ml and ensure that it is alkaline. For the blood and plasma concentration of methotrexate, liver function, and kidney function, we should apply daily inspection.
5, treatment of psoriasis has been rarely applied due to side effects. For treating psoriasis, orally administer 1.25 mg per time with 2 to 3 times per day and 6~9d as a course of treatment.

Adverse reactions and precautions

1. Gastrointestinal reactions include oral mucosal erosion, ulcers, vomiting, and diarrhea with blood in the stool being observed in severe cases.
2. Inhibition of bone marrow granulocyte system with pancytopenis happening in severe cases.
3. Excessive head and neck artery injection or intrathecal injection can cause convulsions.
4. high-dose or long-term medication can cause liver and kidney damage.
5. Additionally, there are hair loss, rashes, and pigmentation, exfoliative dermatitis may also occur; in a few conditions, reproductive dysfunction, irregular menstruation can be observed. It can cause teratogenic fetus or abortion during the early half of pregnancy. 6. Upon intrathecal injection, systemic administration should be paused in order to avoid accumulation of drug for poisoning.
7. Patients of liver and kidney dysfunction should be disabled; pregnant women should take with caution.
8. Salicylates, sulfonamides, phenytoin, tetracycline, chloramphenicol and aminobenzoic acid can enhance the efficacy of the drug with folic acid may reduce the efficacy of the drug.

Drug Interactions

1, Alcohol and other drugs which can cause liver damage, if used in combination with this product, may further increase liver toxicity.
2, since methotrexate can cause increased blood uric acid levels, for patients with gout or hyperuricemia, you should respectively increase the dose of allopurinol and colchicine.
3, the product can enhance the anti-clotting effect, and can even cause lack of liver coagulation factors (and) thrombocytopenia, and therefore we should be cautious for using it in combination with other anticoagulants.
4, with the simultaneous administration of Phenylbutazone and sulfa drugs, because of it competition with protein binding, this product may cause increased serum concentration and lead to toxicity.
5, Oral administration of the kanamycin can increase the absorption of this drug upon oral administration, and oral neomycin may reduce its absorption.
6, Combination with a weak organic acid and salicylate can inhibit the renal excretion of this product, further resulting in increased serum concentrations of the drug. We should reduce the dosage appropriately according to the actual case.
7, Drugs like triamterene and pyrimethamine can have anti-folate effects with simultaneous use of this product being able to increase its side effects.
8, Combination with fluorouracil or first using fluorouracil before administering this drug can both produce antagonism. But if first use this drug and then administer fluorouracil after 4~6h can have synergistic effect. Similarly, this drug, if being used in combination with L-asparaginase can also lead to reduced efficiency, as with the latter 10 days or within 24h after administration of this product to L-asparaginase Instead applying the L-asparaginase at ten days after using the later one or at 24 h within using this product can enhance the efficacy and reduce its side effects on the digestive tract and bone marrow. It has been reported recently applying cytarabine at 24 h before using this product or 10 mins after can increase the anti-cancer activity of this product. We should be cautious when applied methotrexate in combination with radiotherapy or other kinds of drugs on bone marrow suppression.

Chemical Properties

It is orange-yellow crystalline powder. It has a melting point of 185-204 ℃. It is easily soluble in dilute alkali, acid or alkali metal carbonate solution, and slightly soluble in dilute hydrochloric acid but almost insoluble in water, ethanol, chloroform, and ethyl ether.

Production method

It is obtained from the cyclization between 2, 4, 5, 6-tetraaminopyrimidine and dibromo propionaldehyde and further condensation with p-N-Methylaminobenzoylglutamic acid.

Description

Methotrexate is an orange-brown crystalline powder. Molecular weight= 454.50; Freezing/Melting point=185204℃ (decomposes). Insoluble in water.

Chemical Properties

Methotrexate is an orange-brown crystalline powder.

Chemical Properties

Yellow Crystaline Powder

Originator

Methotrexate Lederle,Lederle,US,1955

Uses

Methotrexate is used to treat severe lymphatic leukemia, choriocarcinoma, non-Hodgkin’s lymphoma, bone carcinoma, as well as head, neck, breast, and lung tumors.

Uses

Anti-cancer

Uses

dietary supplement, crosses the blood-brain barrier, potential activities as anxiolytic and vasodilator

Uses

A Folic acid antagonist. Used as a antineoplastic and antirheumatic.

Uses

A deuterated folic acid antagonist

Uses

Used as a antineoplastic and antirheumatic. A folic Acid antagonist

Definition

ChEBI: Methotrexate is a member of pteridines, a monocarboxylic acid amide and a dicarboxylic acid. It has a role as an antineoplastic agent, an antirheumatic drug, an EC 1.5.1.3 (dihydrofolate reductase) inhibitor, a DNA synthesis inhibitor, an abortifacient, a dermatologic drug, an antimetabolite and an immunosuppressive agent. It is functionally related to a L-glutamic acid. It is a conjugate acid of a methotrexate(1-).

Indications

Of the DMARDs, methotrexate (Rheumatrex) is the most widely prescribed. It is indicated for the treatment of rheumatoid arthritis and psoriasis; it is also used for psoriatic arthritis, systemic lupus erythematosus, and sarcoidosis. It is generally as efficacious as the other agents, with a low incidence of serious side effects when prescribed on a low-dose weekly schedule.

Indications

Methotrexate, for example, is highly bound to serum albumin and can be displaced by salicylates, sulfonamides, phenothiazines, phenytoin, and other organic acids. The induction of hepatic drugmetabolizing enzymes by phenobarbital may alter the metabolism of cyclophosphamide to both active and inactive metabolites. Mercaptopurine metabolism is blocked by allopurinol, an occurrence that may result in lethal toxicity if the dosage of mercaptopurine is not reduced to one-fourth of the usual dosage. Methotrexate is secreted actively by the renal tubules, and its renal clearance may be delayed by salicylates.

Indications

Methotrexate competitively inhibits the binding of folic acid to the enzyme dihydrofolate reductase.
Tetrahydrofolate is in turn converted to N⁵,N¹⁰- methylenetetrahydrofolate, which is an essential cofactor for the synthesis of thymidylate, purines, methionine, and glycine. The major mechanism by which methotrexate brings about cell death appears to be inhibition of DNA synthesis through a blockage of the biosynthesis of thymidylate and purines.
Cells in S-phase are most sensitive to the cytotoxic effects of methotrexate. RNA and protein synthesis also may be inhibited to some extent and may delay progression through the cell cycle, particularly from G1 to S.

Indications

Methotrexate is approved for use in severe disabling psoriasis recalcitrant to other less toxic treatments. The standard regimen is similar to low-dose therapy used for the treatment of rheumatoid arthritis . Although toxicities are similar to those described in the treatment of other diseases, hepatic cirrhosis and unexpected pancytopenia are of special concern given the chronicity of treatment.

Manufacturing Process

5 g (15 mmol) of diethyl-p-methylaminobenzoyl-L-glutamate and 8.0 g of aminomalononitrile tosylate (65% by NMR assay, 20 mmol) were dissolved in warm ethanol (65 ml, with 15% water by volume). To this solution, cooled to 0°C, was added all at once and with vigorous stirring, 3.6 g of βbromopyruvaldoxime (89% by NMR assay, 19 mmol). After 30 minutes the stirred mixture, which was allowed to warm slowly to room temperature, was neutralized with powdered NaHCO3 to pH 6, stirring continued for four additional hours, and the resulting mixture filtered through Celite. The filtrate was evaporated under reduced pressure to a glasslike substance, which was taken up in 500 ml of chloroform. The resulting suspension was then filtered using Celite, and the filtrate was washed with water, dried with anhydrous MgSO4, and evaporated to give an orange glasslike substance which was used directly in the next step.
To a 20% solution of titanium trichloride in water (39 mmol), stirred under nitrogen, was added a solution of 18 g (230 mmol) of ammonium acetate in 55 ml of water. Then, to this mixture, cooled to 10°C and stirred with an airdriven stirrer, was added over a period of 5 minutes a solution of the orange glassy substance above distilled in 60 ml of tetrahydrofuran. The mixture was vigorously stirred for 15 minutes while a rapid stream of nitrogen was passed through. After this time, 15 g of powdered sodium sulfite (120 mmol) was added to the mixture, which after several minutes turned from green to yellowish white. This mixture was stirred into 1 liter of chloroform, and the heavy yellow layer separated by use of a separatory funnel. This chloroform layer was washed with water, dried using anhydrous MgSO4, and evaporated under reduced pressure to give a light orange glass, which was then chromatographed rapidly on a column made from 80 g of Baker silica gel, using 5% ethyl acetate in chloroform as the eluent.
The product obtained by evaporation of the eluate was recrystallized from ethanol-ether (1:10) to give a light yellow powder, MP 85 to 88°C. The yield was 4.4 g (63%).
A solution containing 4.8 g (10.2 mmol) of diethyl-N-[p-[[(2-amino-3-cyano5-pyrazinyl)methyl] methylamino]benzoyl]glutamate and 5 g (42 mmol) of guanidine acetate in 40 ml of dimethylformamide was stirred under nitrogen at 120°C for six hours. The resulting solution was cooled to room temperature, filtered and evaporated to a glassy product using a rotary evaporator and a mechanical vacuum pump to insure a better vacuum. The residual glass was taken up in 500 ml of chloroform, the resulting suspension filtered using Celite, and the filtrate washed with water, dried using anhydrous MgSO4, and evaporated to dryness. (The residual material was chromatographed rapidly on a column prepared from 250 g of Baker silica gel using, initially, 2% ethanol in chloroform, and then 5% ethanol in chloroform as eluents.) The material obtained by evaporation of the eluates was crystallized from ethanol-chloroform (4:1) to give small, pale yellow lustrous platelets, MP 142°C to 154°C; yield, 3.8 g (73%). Further crystallization of this material from ethanol-chloroform (4:1) raised the MP to 153°C to 155°C. The compound is completely racemic.
A sample of this product was hydrolyzed in a mixture of water and methanol in the presence of potassium hydroxide. Essentially pure methotrexate was thus obtained.

brand name

Mexate (Bristol-Myers Oncology); Rheumatrex (Wyeth-Ayerst).

Therapeutic Function

Antineoplastic

Biological Functions

Although the mechanism of action of methotrexate in rheumatoid arthritis is unknown, recent studies have shown that methotrexate reversibly inhibits dihydrofolate reductase, blocking the proliferation of B cells by interfering with DNA synthesis, repair, and replication. Oral absorption is dose-dependent, being well-absorbed at doses of 7.5–25 mg once a week. At this dose, oral bioavailability is approximately 60%, and food can delay absorption and reduce peak concentration. The volume of distribution is 0.4 to 0.8 L/kg. Protein binding is approximately 50%. It is metabolized to active metabolites, methotrexate polyglutamates and 7-hydroxymethotrexate. Some metabolism occurs by intestinal flora after oral administration. Methotrexate is actively transported into the urine (80–90% unchanged in the urine within 24 hours) via the folate transporter, an organic anion transporter. Its elimination half-life is 3 to 10 hours.

Acquired resistance

Mammalian cells have several mechanisms of resistance to methotrexate. These include an increase in intracellular dihydrofolate reductase levels, appearance of altered forms of dihydrofolate reductase with decreased affinity for methotrexate, and a decrease in methotrexate transport into cells. The relative importance of each of these mechanisms of resistance in various human tumors is not known.
Cellular uptake of the drug is by carrier-mediated active transport. Drug resistance due to decreased transport can be overcome by greatly increasing extracellular methotrexate concentration, which provides a rationale for high-dose methotrexate therapy. Since bone marrow and gastrointestinal cells do not have impaired folate methotrexate transport, these normal cells can be selectively rescued with reduced folate, bypassing the block of dihydrofolate reductase. Leucovorin (citrovorum factor, folinic acid, 5-formyltetrahydrofolate) is the agent commonly used for rescue.

General Description

Methotrexate (MTX, Rheumatrex), an antifolate drug used in cancer treatment, has also been used in the disease management of RA since the 1950s. Because of its quicker therapeutic onset among all DMARDs and its demonstrated efficacy, tolerability, and low cost, MTX has been the firstline therapy for RA patients who are not responsive to NSAIDs alone.
Recent findings have indicated that other DMARDs should only be used for patients who are refractory to MTX. At least four anti-inflammatory mechanisms of action have been suggested for MTX’s ability to slow down RA disease progression. First, MTX, being a folate antagonist, prevents antigen-dependent T-cell proliferation by blocking de novo pyrimidine biosynthesis, via a reversible inhibition of dihydrofolate reductase. It also inhibits folate-mediated production of spermine and spermidine in synovial tissue. These polyamines are believed to be the toxic compounds responsible for causing tissue injury in RA. MTX can also reduce intracellular glutathione concentration, thereby altering the cellular redox state that suppresses the formation of reactive oxygen radicals in synovial tissue. Lastly, MTX, similar to sulfasalazine, infliximab, and IL-4, can also inhibit osteoclastogenesis (i.e., bone erosion) in patients with RA, by modulating the interaction of the receptor activator of nuclear factor B, its ligand, and osteoprotegrin.

General Description

Odorless yellow to orange-brown crystalline powder.

General Description

The drug is available in 50-, 100-, 200-, and 1,000-mg vialsfor IV use. Methotrexate is used to treat several cancer typesincluding breast cancer, bladder cancer, colorectal cancer,and head and neck cancer. The mechanism of action ofmethotrexate involves inhibition of DHFR leading to a depletionof critical reduced folates. The reduced folates arenecessary for biosynthesis of several purines and pyrimidines.Resistance to methotrexate can occur because ofdecreased carrier-mediated transport of drug into cells orincreased expression of the target enzyme DHFR. Oralbioavailability varies with dose because of saturable uptakeprocesses, and high doses are required to reach therapeuticlevels in the CNS. The majority of drug dosage is excretedunchanged in the urine. The renal excretion of methotrexateis inhibited by several carboxylic acid drugs such as penicillins,probenecid, nonsteroidal anti-inflammatory agents,and aspirin. Methotrexate enhances 5-FU antitumor effectswhen given 24 hours prior to the fluoropyrimidine.Methotrexate toxicity includes myelosuppression, mucositis,nausea, vomiting, severe headaches, renal toxicity, acutecerebral dysfunction, skin rash, and hyperpigmentation.

Air & Water Reactions

Methotrexate is sensitive to hydrolysis, oxidation and light. Insoluble in water.

Reactivity Profile

Methotrexate decomposes in very acidic or alkaline conditions. Methotrexate is incompatible with strong oxidizing agents and strong acids.

Hazard

Very toxic. Questionable carcinogen.

Fire Hazard

Flash point data for Methotrexate are not available; however, Methotrexate is probably combustible.

Biological Activity

Cytotoxic agent. Inhibits thymidylate synthetase and de novo purine synthesis. Potent folic acid antagonist; inhibits dihydrofolate reductase. Also inhibits Ras carboxyl methylation in DKOB8 cells, leading to decreased p44 and Akt activation.

Mechanism of action

Methotrexate is a folic acid antagonist structurally designed to compete successfully with 7,8-DHF for the DHFR enzyme. The direct inhibition of DHFR causes cellular levels of 7,8-DHF to build up, which in turn results in feedback (indirect) inhibition of thymidylate synthase. Methotrexate also is effective in inhibiting glycine amide ribonucleotide (GAR) transformylase , a key enzyme in the synthesis of purine nucleotides. Take note of the structural differences between methotrexate and DHF, because these differences will be important to an understanding of the chemical mechanism of this anticancer agent.

Pharmacology

Methotrexate is a folate antimetabolite that inhibits dihydrofolate reductase and other folate-dependent enzymes in cells. At the low doses used in the therapy of rheumatoid arthritis,methotrexate appears to be acting more as an antiinflammatory agent than as an immunosuppressant. Methotrexate inhibits folate-dependent enzymes involved in adenosine degradation, increasing concentrations of extracellular adenosine. Adenosine acts via cell surface receptors to inhibit the production of inflammatory cytokines such as TNF-α and IFN-γ.Methotrexate also decreases the production of inflammatory prostaglandins and proteases, though a direct action on the COX enzymes has not been noted.

Pharmacology

Methotrexate is well absorbed orally and at usual dosages is 50% bound to plasma proteins. The plasma decay that follows an intravenous injection is triphasic, with a distribution phase, an initial elimination phase, and a prolonged elimination phase. The last phase is thought to reflect slow release of methotrexate from tissues. The major routes of drug excretion are glomerular filtration and active renal tubular secretion.
The formation of polyglutamic acid conjugates of methotrexate has been observed in tumor cells and in the liver and may be an important determinant of cytotoxicity. These methotrexate polyglutamates are retained in the cell and are also potent inhibitors of dihydrofolate reductase.

Clinical Use

Methotrexate is part of curative combination chemotherapy for acute lymphoblastic leukemias, Burkitt’s lymphoma, and trophoblastic choriocarcinoma. It is also useful in adjuvant therapy of breast carcinoma; in the palliation of metastatic breast, head, neck, cervical, and lung carcinomas; and in mycosis fungoides.
High-dose methotrexate administration with leucovorin rescue has produced remissions in 30% of patients with metastatic osteogenic sarcoma.
Methotrexate is one of the few anticancer drugs that can be safely administered intrathecally for the treatment of meningeal metastases. Its routine use as prophylactic intrathecal chemotherapy in acute lymphoblastic leukemia has greatly reduced the incidence of recurrences in the CNS and has contributed to the cure rate in this disease. Daily oral doses of methotrexate are used for severe cases of the nonneoplastic skin disease psoriasis, and methotrexate has been used as an immunosuppressive agent in severe rheumatoid arthritis.

Side effects

In the low-dose regimen used for rheumatoid arthritis, most side effects of methotrexate are mild and can be managed by temporarily stopping the drug or reducing the dose. These include nausea, stomatitis, GI discomfort, rash, diarrhea, and headaches. Changes in liver aminotransferases and mild to moderate immunosuppression have been reported in rheumatoid arthritis patients taking methotrexate. Severe toxicity is possible but rare and may be a function of drug accumulation. These effects include hepatotoxicity progressing to cirrhosis, pneumonitis progressing to pulmonary fibrosis, and bone marrow depression with anemia, leukopenia, and thrombocytopenia. Folic acid supplementation is often used to alleviate certain side effects of methotrexate therapy (stomatitis, GI irritation, hematopoietic effects) but may also contribute to resistance to this therapy.

Side effects

Myelosuppression is the major dose-limiting toxicity associated with methotrexate therapy. Gastrointestinal toxicity may appear in the form of ulcerative mucositis and diarrhea. Nausea, alopecia, and dermatitis are common with high-dose methotrexate. The greatest danger of high-dose therapy is renal toxicity due to precipitation of the drug in the renal tubules, and the drug should not be used in patients with renal impairment. Intrathecal administration may produce neurological toxicity ranging from mild arachnoiditis to severe and progressive myelopathy or encephalopathy. Chronic lowdose methotrexate therapy, as used for psoriasis, may result in cirrhosis of the liver. Occasionally methotrexate produces an acute, potentially lethal lung toxicity that is thought to be allergic or hypersensitivity pneumonitis. Additionally, methotrexate is a potent teratogen and abortifacient.

Synthesis

Methotrexate, N-[p-[[2,4-diamino-6-piperidinyl)methyl]methylamino]- benzoyl]-L-(
)-glutamic acid (30.1.1.8), is made by reacting N-(4-methylaminobenzoyl)glutaminic acid (30.1.1.3) with 2-amino-4-hydroxyl-6-bromomethylpteridine(30.1.1.7). In order to do this, N-(4-methylaminobenzoyl)glutaminic acid (30.1.1.3) is synthesized from 4-nitrobenzoyl chloride, which is reacted with L-glutamic acid, forming N-(4-nitrobenzoyl)glutamic acid (30.1.1.1), the nitro group of which is reduced to an amino group using hydrogen over Raney nickel, which gives N-(4-aminobenzoyl)glutamic acid (30.1.1.2). This undergoes reductive methylation using formaldehyde and hydrogen, which forms N-(4-methylaminobenzoyl)glutamic acid (30.1.1.3).
The second part of the methotrexate molecule, 2-amino-4-hydroxy-6-bromomethylpteridine (30.1.1.7), is made from 2,4,6-triaminopyrimidine (30.1.1.4), which is easily synthesized by reacting malonic acid dinitrile with guanidine. This is nitrosylated by anhydrous nitrous acid to 2,4,6-triamino-5-nitrosopyrimidine (30.1.1.5), and then it is reduced by sodium borohydride to 2,4,5,6-tetraaminopyrimidine (30.1.1.6). Upon reacting this with 1,2- dibromopropionic aldehyde, the product of attaching bromine to acrolein, 2-amino-4- hydroxy-6- bromomethyl-pteridine (30.1.1.7) is formed. Alkylating the amine nitrogen atom of N-(4-methylaminbenzoyl)glutamic acid (30.1.1.3) with resulting bromide (30.1.1.7) gives methotrexate (30.1.1.8).

Potential Exposure

Methotrexate is an alkaloid anticancer drug available in tablet or injectable liquid form. A chemotherapy drug that interferes with DNA and RNA synthesis. It is also an insect chemosterilant.

Veterinary Drugs and Treatments

Indicated for lymphomas and some solid tumors in dogs and cats. In human medicine, methotrexate is also being used to treat refractory rheumatoid arthritis and severe psoriasis.

Drug interactions

Potentially hazardous interactions with other drugs
Anaesthetics: antifolate effect increased by nitrous oxide - avoid.
Analgesics: increased risk of toxicity with NSAIDs - avoid.
Antibacterials: absorption possibly reduced by neomycin; antifolate effect increased with co-trimoxazole and trimethoprim; penicillins and possibly ciprofloxacin reduce excretion of methotrexate (increased risk of toxicity); increased haematological toxicity with doxycycline, sulphonamides and tetracycline.
Antiepileptics: concentration possibly increased by levetiracetam.
Antimalarials: antifolate effect enhanced by pyrimethamine.
Antipsychotics: avoid with clozapine (increased risk of agranulocytosis).
Ciclosporin: methotrexate may inhibit the clearance of ciclosporin or its metabolites; ciclosporin may inhibit methotrexate elimination.
Corticosteroids: increased risk of haematological toxicity.
Cytotoxics: effects of methotrexate antagonised by asparaginase, crisantaspase and pegasparagase - give asparaginase, crisantaspase and pegasparagase 24 hours after methotrexate; increased pulmonary toxicity with cisplatin.
Leflunomide: risk of toxicity.
Probenecid: excretion of methotrexate reduced.
Retinoids: concentration increased by acitretin, also increased hepatotoxicity - avoid.
Ulcer-healing drugs: PPIs may reduce high dose methotrexate elimination; consider temporarily stopping PPI

First aid

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

Metabolism

Methotrexate can be given orally in the treatment of breast, head and neck, and various lung cancers as well as in non-Hodgkin's lymphoma. The sodium salt form also is marketed for IV, intramuscular, intra-arterial, or intrathecal injection. Oral absorption is dose-dependent and peaks at 80 mg/m2 because of site saturation. The monoglutamate tail of methotrexate permits active transport into cells, with carrier-mediated transport predominating at serum concentration levels lower than 100 μM. Once inside the cell, methotrexate undergoes a polyglutamation reaction that adds several anionic carboxylate groups to trap the drug at the site of action. Polyglutamation is more efficient in tumor cells than in healthy cells and, therefore, may promote selective toxicity of this drug. Cancer cells can become resistant to methotrexate over time which may involve impaired transport across tumor cell membranes, enhanced efflux from the tumor cell, and attenuated polyglutamation rates. The polyglutamated drug will be hydrolyzed back to the parent structure before renal elimination. Up to 90% of an administered dose of methotrexate is excreted unchanged in the urine within 24 hours.

storage

Store at RT

Shipping

UN1544 Alkaloids, solid, n.o.s. or Alkaloid salts, solid, n.o.s. poisonous, Hazard Class: 6.1; Labels: 6.1- Poisonous materials, Technical Name Required. UN2811 Toxic solids, organic, n.o.s., Hazard Class: 6.1; Labels: 6.1- Poisonous materials, Technical Name Required.

Purification Methods

Most common impurities are 10-methylpteroylglutamic acid, aminopterin and pteroylglutamic acid. Purify it by chromatography on Dowex-1 acetate, followed by filtration through a mixture of cellulose and charcoal. It has been recrystallised from aqueous HCl or by dissolution in the minimum volume of N NaOH and acidified until precipitation is complete, filter or better collect by centrifugation, wash with H2O (also by centrifugation) and dry at 100o/3mm. It has UV: max at 244 and 307nm ( 17300 and 19700) in H2O at pH 1; 257, 302 and 370nm ( 23000, 22000 and 7100) in 2O at pH 13. [Momle Biochemical Preparations 8 20 1961, Seeger et al. J Am Chem Soc 71 1753 1949.] It is a potent inhibitor of dihydrofolate reductase and is used in cancer chemotherapy. [Blakley The Biochemistry of Folic Acid and Related Pteridines, North-Holland Publ Co., Amsterdam, NY, pp157-163 1969, Beilstein 26 IV 3833.] It is CARCINOGENIC; HANDLE WITH EXTREME CARE.

Incompatibilities

Combustible. Compounds of the carboxyl group react with all bases, both inorganic and organic (i.e., amines) releasing substantial heat, water and a salt that may be harmful. Incompatible with arsenic compounds (releases hydrogen cyanide gas), diazo compounds, dithiocarbamates, isocyanates, mercaptans, nitrides, and sulfides (releasing heat, toxic, and possibly flammable gases), thiosulfates and dithionites (releasing hydrogen sulfate and oxides of sulfur). Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides, light, UV, moisture.

Waste Disposal

It is inappropriate and possibly dangerous to the environment to dispose of expired or waste drugs and pharmaceuticals by flushing them down the toilet or discarding them to the trash. Household quantities of expired or waste pharmaceuticals may be mixed with wet cat litter or coffee grounds, double-bagged in plastic, discard in trash. Larger quantities shall carefully take into consideration applicable DEA, EPA, and FDA regulations. If possible return the pharmaceutical to the manufacturer for proper disposal being careful to properly label and securely package the material. Alternatively, the waste pharmaceutical shall be labeled, securely packaged and transported by a state licensed medical waste contractor to dispose by burial in a licensed hazardous or toxic waste landfill or incinerator.

Precautions

Methotrexate is teratogenic and is contraindicated duringpregnancy and breast-feeding. Prior to attemptingpregnancy, women should wait at least one menstrualcycle and men at least 3 months after discontinuing thisdrug. Additional contraindications to methotrexate administrationinclude kidney, liver, and lung disease;moderate to high alcohol use; immunodeficiency; blooddyscrasias; and hypersensitivity. Elderly persons may be at increased risk for toxicity because of decreased renaland hepatic function.
Methotrexate clearance can be decreased by thecoadministration of NSAIDs; however, this not usuallya problem with the low doses of methotrexate used totreat arthritis. Methotrexate can be displaced fromplasma protein binding sites by phenylbutazone, phenytoin,sulfonylureas, and sulfonamides and certain otherantibiotics. The antifolate effects of methotrexate areadditive with those of other folate-inhibitory drugs,such as trimethoprim.