Merex

Merex Uses, Dosage, Side Effects, Food Interaction and all others data.

Merex 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 p.r.n. 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. When cellular proliferation in malignant tissues is greater than in most normal tissues, methotrexate may impair malignant growth without irreversible damage to normal tissues

Merex inhibits enzymes responsible for nucleotide synthesis which prevents cell division and leads to anti-inflammatory actions. It has a long duration of action and is generally given to patients once weekly. Merex has a narrow therapeutic index.

Do not take methotrexate daily.

Trade Name Merex
Availability Prescription only
Generic Methotrexate
Methotrexate Other Names Amethopterin, Methotrexat, Méthotrexate, Methotrexate, Methotrexatum, Metotrexato
Related Drugs Humira, Opdivo, Cosentyx, prednisone, dexamethasone, hydroxychloroquine, Plaquenil, Decadron, Enbrel, Remicade
Type Injection
Formula C20H22N8O5
Weight Average: 454.4393
Monoisotopic: 454.171315854
Protein binding

Methotrexate is 46.5-54% bound to plasma proteins.

Groups Approved
Therapeutic Class Antidote preparations, Immunosuppressant
Manufacturer Intas Pharmaceuticals Ltd
Available Country India
Last Updated: September 19, 2023 at 7:00 am
Merex
Merex

Uses

Neoplastic Diseases: Merex is used for the treatment of gestational choriocarcinoma, chorioadenoma destruens and hydatidiform mole. Merex is used in maintenance therapy in combination with other chemotherapeutic agents. Merex is used alone or in combination with other anticancer agents in the treatment of breast cancer, epidermoid cancers of the head and neck, advanced mycosis fungoides (cutaneous T cell lymphoma), and lung cancer, particularly squamous cell and small cell types. Merex is also used in combination with other chemotherapeutic agents in the treatment of advanced stage non-Hodgkin's lymphomas.

Psoriasis: Merex is used for the symptomatic control of severe, recalcitrant, disabling psoriasis that is not adequately responsive to other forms of therapy, but only when the diagnosis has been established, as by biopsy and/or after dermatologic consultation. It is important to ensure that a psoriasis “flare” is not due to an undiagnosed concomitant disease affecting immune responses.

Rheumatoid Arthritis Including Polyarticular-Course Juvenile Rheumatoid Arthritis: Merex is used for the management of selected adults with severe, active, rheumatoid arthritis (ACR criteria), or children with active polyarticular course juvenile rheumatoid arthritis, who have had an insufficient therapeutic response to, or are intolerant of, an adequate trial of first-line therapy including full dose non-steroidal anti-inflammatory agents (NSAIDs).

Aspirin, NSAIDs, and/or low dose steroids may be continued, although the possibility of increased toxicity with concomitant use of NSAIDs including salicylates has not been fully explored. Steroids may be reduced gradually in patients who respond to methotrexate. Combined use of methotrexate with gold, penicillamine, hydroxychloroquine, sulfasalazine, or cytotoxic agents, has not been studied and may increase the incidence of adverse effects. Rest and physiotherapy as used should be continued.

Merex is also used to associated treatment for these conditions: Acute Lymphocytic Leukemia (ALL), Acute Promyelocytic Leukemia (APL), Breast Cancer, Cancer, Bladder, Central Nervous System Lymphoma, Choriocarcinoma, Crohn's Disease (CD), Dermatomyositis, Disseminated Sclerosis, Extrauterine Pregnancy, Graft Versus Host Disease (GVHD), Head and Neck Carcinoma, Hydatidiform Mole, Meningeal leukemia, Polymyositis, Sarcoma, Osteogenic, Small Cell Lung Cancer (SCLC), Soft Tissue Sarcoma (STS), Squamous Cell Carcinoma of Lung, Systemic Lupus Erythematosus (SLE), Uveitis, Active Pauciarticular juvenile rheumatoid arthritis, Advanced Alibert-Bazin syndrome, Advanced non-Hodgkin lymphoma, Nonleukemic meningeal cancer, Refractory Takayasu arteritis, Severe Psoriasis, Severe, active Rheumatoid arthritis, Medically induced abortion

How Merex works

Merex enters tissues and is converted to a methotrexate polyglutamate by folylpolyglutamate.

Merex's mechanism of action is due to its inhibition of enzymes responsible for nucleotide synthesis including dihydrofolate reductase, thymidylate synthase, aminoimidazole caboxamide ribonucleotide transformylase (AICART), and amido phosphoribosyltransferase. Inhibtion of nucleotide synthesis prevents cell division.

In rheumatoid arthritis, methotrexate polyglutamates inhibit AICART more than methotrexate. This inhibition leads to accumulation of AICART ribonucleotide, which inhibits adenosine deaminase, leading to an accumulation of adenosine triphosphate and adenosine in the extracellular space, stimulating adenosine receptors, leading to anti-inflammatory action.

Dosage

Merex dosage

Oral-

  • Choriocarcinoma: 15-30 mg daily for 5 days, repeat after an interval of ≥1 wk for 3-5 courses.
  • Acute lymphoblastic leukaemia: Maintenance: 15 mg/m2 once or twice wkly, with other agents.
  • Burkitt's lymphoma: 10-25 mg daily for 4-8 days, repeated after 7-10 days.
  • Psoriasis: 10-25 mg wkly as a single dose, adjust subsequent doses based on response.
  • Rheumatoid arthritis: 7.5 mg once wkly, adjust by response. Not more than 20 mg/wk.
  • Mycosis fungoides: 2.5-10 mg daily to induce remission.
  • Crohn's disease: 12.5-22.5 mg once wkly for up to 1 yr.

Parenteral-

  • Psoriasis: 10-25 mg wkly as a single dose. Adjust subsequent doses based on response. May be given via IV/IM admin.

Intramuscular-

  • Choriocarcinoma: 15-30 mg daily for 5 days. Repeat after at least 1 wk for 3-5 courses. Alternatively, 0.25-1 mg/kg (max: 60 mg) every 48 hr for 4 doses followed by folinic acid rescue, repeat at intervals of 7 days for 4 or more courses.
  • Mycosis fungoides: 50 mg wkly as a single dose or 2 divided doses.
  • Acute lymphoblastic leukaemia: Maintenance: 15 mg/m2 once or twice wkly, with other agents.
  • Crohn's disease: 25 mg once wkly for 16 wk. Maintenance: 15 mg wkly.

Intrathecal-

  • Meningeal leukaemia: 12 mg/m2 (max 15 mg) once wkly for 2-3 wk, then once mthly. Alternatively, 200-500 mcg/kg every 2-5 day until CSF cell count is normalised.

Intravenous-

  • Osteosarcoma: Initial recommended dose: 12 g/m2 as a 4-hr infusion, followed by folinic acid, as part of combined therapy. May increase dose to 15 g/m2 in subsequent treatments if initial dosage is insufficient to achieve peak serum methotrexate levels of 454 mcg/mL at the end of the infusion. Merex infusion is administered on postoperative wk 4, 5, 6, 7, 11, 12, 15, 16, 29, 30, 44 and 45; in combination with other chemotherapy agents. Folinic acid can be given orally, IM or IV inj starting 24 hr after the beginning of the methotrexate infusion. Give via parenteral routes If patient experiences GI toxicity (e.g., nausea, vomiting). Usual dosage of folinic acid: 15 mg every 6 hr for a total of 60 hr or a total of 10 doses.
  • Breast cancer: 10-60 mg/m2 often with cyclophosphamide and fluorouracil.
  • Advanced lymphosarcoma: Up to 30 mg/kg, followed by folinic acid rescue.
  • Acute lymphoblastic leukaemia: Maintenance: 2.5 mg/kg every 14 days.

Should be taken on an empty stomach. Best taken on an empty stomach. May be taken with meals to reduce GI discomfort. Avoid taking with milk-rich products.

Intramuscular: Dilute powder with D5W or normal saline to a concentration ≤25 mg/ml (20 mg and 50 mg vials) and 50 mg/ml (1 g vial).

Intrathecal: Reconstitute to 2.5-5 mg/ml with normal saline, D5W, lactated Ringer's, or Elliott's B solution. Use preservative-free preparations.

Intravenous: Dilute powder with D5W or normal saline to a concentration ≤25 mg/ml (20 mg and 50 mg vials) and 50 mg/ml (1 g vial).

Parenteral: Dilute powder with D5W or normal saline to a concentration ≤25 mg/ml (20 mg and 50 mg vials) and 50 mg/ml (1 g vial).

Side Effects

Ulceration of the mouth and GI disturbances (e.g. stomatitis and diarrhoea), bone marrow depression, hepatotoxicity, renal failure, skin reactions, alopecia, ocular irritation, arachnoiditis in intrathecal use, megaloblastic anaemia, osteoporosis, precipitation of diabetes, arthralgias, necrosis of soft tissue and bone, anaphylaxis, impaired fertility.

Toxicity

The oral LD50 in rats is 135mg/kg and in mice is 146mg/kg.

Symptoms of overdose include hematologic and gastrointestinal reactions like leukopenia, thombocytopenia, anemia, pancytopenia, bone marrow suppression, mucositis, stomatitis, oral ulceration, nausea, vomiting, gastrointestinal ulceration, and gastrointestinal bleeding. In the event of an overdose, patients should be treated with glucarpidase and not be given leucovorin for 2 hours before or after glucarpidase.

Precaution

Hepatic or renal impairment, bone marrow depression, elderly, neonates. Ulcerative disorders of the GI tract. Monitor haematological, renal and hepatic function, and GI toxicity regularly.

Interaction

Decreased effectiveness with folic acid and its derivatives.

Food Interaction

  • Avoid alcohol.
  • Avoid milk and dairy products. Milk and dairy products reduce absorption.
  • Exercise caution with St. John's Wort.
  • Limit caffeine intake. Caffeine may reduce the effectiveness of methotrexate.
  • Take with or without food.

[Moderate] MONITOR: Limited data suggest that consumption of greater than 180 mg

The exact mechanism of interaction is unknown but may be related to the antagonistic effect of caffeine on adenosine receptors, as anti-inflammatory properties of MTX is thought to result from the accumulation of adenosine.

In a study of 39 patients treated with MTX 7.5 mg

There were no significant differences between the responses of patients with moderate caffeine intake (120 to 180 mg

In an interview of 91 patients treated with MTX, 26% of patients who discontinued the drug were regular coffee drinkers compared to only 2% of those still receiving the drug.

Because treatment failure was the reason for MTX discontinuation in 80% of patients who discontinued, the investigators suggested that caffeine may have interfered with MTX efficacy.

MANAGEMENT: Until further information is available, the potential for interaction should be considered in patients who consume substantial amounts of caffeine and caffeine-containing foods and are prescribed methotrexate for rheumatoid arthritis.

It may be appropriate to limit caffeine intake if an interaction is suspected in cases of treatment failure.

Merex Alcohol interaction

[Moderate]

Coadministration of methotrexate with other agents known to induce hepatotoxicity may potentiate the risk of liver injury.

Merex, especially at higher doses or with prolonged treatment, has been associated with hepatotoxicity including acute hepatitis, chronic fibrosis, necrosis, cirrhosis, and liver enzyme elevations.

The risk of hepatic injury should be considered when methotrexate is used with other potentially hepatotoxic agents (e.g., acetaminophen; alcohol; androgens and anabolic steroids; antituberculous agents; azole antifungal agents; ACE inhibitors; cyclosporine (high dosages); disulfiram; endothelin receptor antagonists; interferons; ketolide and macrolide antibiotics; kinase inhibitors; minocycline; nonsteroidal anti-inflammatory agents; nucleoside reverse transcriptase inhibitors; proteasome inhibitors; retinoids; sulfonamides; tamoxifen; thiazolidinediones; tolvaptan; vincristine; zileuton; anticonvulsants such as carbamazepine, hydantoins, felbamate, and valproic acid; lipid-lowering medications such as fenofibrate, lomitapide, mipomersen, niacin, and statins; herbals and nutritional supplements such as black cohosh, chaparral, comfrey, DHEA, kava, pennyroyal oil, and red yeast rice).

Baseline and periodic monitoring of hepatic function is recommended, while liver biopsy may be warranted during long-term use of methotrexate.

Patients should be advised to seek medical attention if they experience potential signs and symptoms of hepatotoxicity such as fever, rash, itching, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, pale stools, and jaundice.

Volume of Distribution

The volume of distribution of methotrexate at steady state is approximately 1L/kg.

Elimination Route

Merex has a bioavailability of 64-90%, though this decreases at oral doses above 25mg due to saturation of the carrier mediated transport of methotrexate.. Merex has a Tmax of 1 to 2 hours. oral doses of 10-15µg reach serum levels of 0.01-0.1µM.

Half Life

The half life of low dose methotrexate is 3 to 10 hours in adults. The half life for high dose methotrexate is 8 to 15 hours. Pediatric patients taking methotrexate for acute lymphoblastic anemia experience a terminal half life of 0.7 to 5.8 hours. Pediatric patients taking methotrexate for juvenile idiopathic arthritis experience a half life of 0.9 to 2.3 hours.

Clearance

Merex clearance varies widely between patients and decreases with increasing doses. Currently, predicting clearance of methotrexate is difficult and exceedingly high serum levels of methotrexate can still occur when all precautions are taken.

Elimination Route

Merex is >80% excreted as the unchanged drug and approximately 3% as the 7-hydroxylated metabolite. Merex is primarily excreted in the urine with 8.7-26% of an intravenous dose appearing in the bile.

Pregnancy & Breastfeeding use

Pregnancy category X. Studies in animals or human beings have demonstrated fetal abnormalities or there is evidence of fetal risk based on human experience or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.

Contraindication

Severe renal or hepatic impairment, pre-existing profound bone marrow suppression in patients with psoriasis or rheumatoid arthritis, alcoholic liver disease, AIDS, pre-existing blood dyscrasias, pregnancy (in patients with psoriasis or rheumatoid arthritis), breast-feeding.

Acute Overdose

Nausea, vomiting, alopecia, melena, and renal failure.

Storage Condition

Store at room temperature (15-25°C).

Innovators Monograph

You find simplified version here Merex

Merex contains Methotrexate see full prescribing information from innovator Merex Monograph, Merex MSDS, Merex FDA label

FAQ

What is Merex used for?

Merex is used to treat cancer, autoimmune diseases, and ectopic pregnancy and for medical abortions. It is used to treat inflammatory conditions, including: rheumatoid arthritis.

How safe is Merex?

Merex is one of the most effective and widely used medications for treating inflammatory types of arthritis. It's also one of the safest arthritis drugs, despite a common misconception among many patients that methotrexate is highly toxic.

How does Merex work?

Merex work by causing cells to release a molecule that block chemicals that promote inflammation, according to the Arthritis Foundation.

What are the common side effects of Merex?

Merex may cause side effects: 

  • drowsiness.
  • headache.
  • swollen, tender gums.
  • decreased appetite.
  • reddened eyes.
  • hair loss.

Is Merex safe during pregnancy?

This Merex should be used in the treatment of neoplastic diseases only when the potential benefit outweighs the risk to the fetus. Merex can cause teratogenic effects or fetal death when administered to a pregnant woman. It's may impairs fertility.

Is Merex safe during breastfeeding?

Merex is excreted in breast milk in low concentrations and can accumulate in neonatal tissues; thus, it is contraindicated during breastfeeding.

Can I drink alcohol with Merex?

Patients may drink alcohol whilst taking long-term low weekly doses of Merex  for skin conditions, rheumatoid arthritis and other inflammatory conditions, but they should be advised that both alcohol and Merex can potentially damage the liver, so they should not drink more alcohol than recommended by national guidelines.

Can I drive after taking Merex?

Merex may make you dizzy or sleepy. You may need someone to help take you home after your infusion. You shouldn't drive or use machinery while you're on this medication until you know you can function normally.

When should be taken of Merex?

Pharmacokinetic variables suggest that Merex can be administered either in the morning (10 AM) or evening (6 PM) in the treatment of RA.

Does I take Merex on an empty stomach?

Merex should be taken on an empty stomach with a glass of water.

How many time can I take Merex daily?

Take Merex 2.5 mg Tablet only once a week.

How much Merex can I take daily?

Adults, 2.5 milligrams (mg) 2 to 4 times a week. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 10 mg per week. Children, use and dose must be determined by your doctor.

How long does Merex take to work?

Merex can take a while to start working, so it could be up to 12 weeks before you start to notice any difference, but you should still keep taking it.

What is the half life of Merex?

The terminal half-life reported for Merex is approximately three to ten hours for patients receiving treatment for psoriasis, or rheumatoid arthritis or low dose antineoplastic therapy (less than 30 mg/m2).

How long one can take Merex?

If you are taking Merex to treat rheumatoid arthritis, it may take 3 to 6 weeks for your symptoms to begin to improve, and 12 weeks or longer for you to feel the full benefit of Merex. Continue to take Merex even if you feel well.

Who should not take Merex?

Do not use methotrexate to treat psoriasis or rheumatoid arthritis if you have low blood cell counts, a weak immune system, alcoholism or chronic liver disease, or if you are breastfeeding.

What happens if I overdose?

Seek emergency medical attention. An overdose of methotrexate can be fatal. Overdose symptoms may include bruising or unusual bleeding, mouth sores, vomiting, little or no urination, bloody or tarry stools, or coughing up blood or vomit that looks like coffee grounds.

What happen If I missed Merex?

If you miss your dose, you can take it the next day safely. This medicine needs to be given on a fixed schedule. If you miss a dose or forget to use your medicine, call your doctor or pharmacist for instructions.

What happen If I stop taking Merex?

Patients who stopped taking Merex reported having substantially more gastrointestinal issues — including nausea, abdominal pain, and loss of appetite — from Merex than current users did.

Can Merex affects my heart ?

Among patients with rheumatoid arthritis, higher C‐reactive protein was associated with greater heart failure risk, while Merex use was associated with lower risk.

Can Merex affect my kidneys?

Merex can lead to kidney injury at high doses for cancer and is contraindicated in advanced CKD.

Can Merex affects my liver?

Merex can produce many unwanted side effects and can alter liver cells, leading to liver damage and cirrhosis.

*** Taking medicines without doctor's advice can cause long-term problems.
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