1. Methotrexate Pharm D student: Noha Alaa El Dine
Alexandria University Hospitals
Supervised by: Prof. Nashaat Lotfy
Professor of Oncology Faculty of Medicine

2. thus inhibit DNA synthesis
Mechanism of action
MTX is an antifolate belonging to the antimetabolite class of antineoplastic agents.
MTX is a cell cycle specific chemotherapeutic agents that acts on S-phase &
thus inhibit DNA synthesis
Folic acid
Dihydrofolate reductase
Tetrahydrofolic
acid
You can see that the nitrogen group has a CH3 on it and there is an OH group in the double ring instead of an NH2 group. Enough to make a difference in a biosynthesis scheme!
At two stages in the biosynthesis of purines (adenine and guanine) and at one stage in the synthesis of pyrimidines (thymine, cytosine, and uracil), one-carbon transfer reactions occur which require specific coenzymes.These coenzymes are synthesized in the cell from tetrahydrofolic acid. Tetrahydrofolic acid itself is synthesized in the cell from folic acid with the help of an enzyme, folic acid reductase. Methotrexate looks a lot like folic acid to the enzyme, so it binds to it thinking that it is folic acid. In fact, methotrexate looks so good to the enzyme that it binds to it quite strongly. All the folic acid reductase enzymes in the cell bind merrily to the methotrexate and ignore any folic acid they might see. Thus, DNA synthesis cannot proceed because the coenzymes needed for one-carbon transfer reactions are not produced from tetrahydrofolic acid because there is no tetrahydrofolic acid. Again, without DNA, no cell division.
THF included at two stages in the biosynthesis of purines (adenine and guanine) and at one stage in the synthesis of pyrimidines (thymine, cytosine, and uracil)

3. In de novo synthesis, IMP is the first nucleotide formed
In de novo synthesis, IMP is the first nucleotide formed. It is then converted to either AMP or GMP.
Methotrexate also has immunosuppressive activity, in part possibly as a result of inhibition of lymphocyte multiplication.

4. Indications Unlabeled Uses: All Labeled Uses: Acute Lymphoid Leukemia
Breast Carcinoma
Burkitt's Lymphoma
Diffuse Large B-Cell Lymphoma
Gestational Trophoblastic Neoplasm
Juvenile Rheumatoid Arthritis
Locally Advanced Breast Carcinoma
Lung Carcinoma
Malignant Tumor of Head and Neck
Metastatic Breast Carcinoma
Mycosis Fungoides
Psoriasis
Rheumatoid Arthritis
Small Cell Lung Carcinoma
Unlabeled Uses: 
Acute Myeloid Leukemia
Acute Promyelocytic Leukemia
Colorectal Cancer
Ectopic Pregnancy
Malignant Tumor of Cervix
Malignant Tumor of Urinary Bladder
Metastatic Colorectal Cancer
Polymyositis
Psoriatic Arthritis
Systemic Dermatomyositis
Systemic Lupus Erythematosus
Vasculitis
Wegener's Granulomatosis
High-dose methotrexate with leucovorin rescue in patients with unresectable non-small cell carcinoma of the lung. the overall 10% response rate does not appear to be significantly different than the results with standard-dose methotrexate.

5. Protocols Trophoblastic Neoplasms
The usual dosage of methotrexate is 15–30 mg daily, administered orally or IM for 5 days.
A repeat course may be given after a period of one or more weeks provided all signs of residual toxicity have disappeared.
Three to five courses of therapy are usually employed.
Therapy is usually evaluated by 24-hour quantitative analysis of urinary chorionic gonadotropin which should return to normal or less than 50 IU/24 hours, usually after the third or fourth course.
Complete resolution of measurable lesions usually occurs 4–6 weeks later.
One or two courses of methotrexate therapy are usually given after normalization of urinary chorionic gonadotropin hormone concentrations is achieved.
In the treatment of trophoblastic disease in women, regimens alternating courses of methotrexate therapy and dactinomycin therapy or combining administration of methotrexate and mercaptopurine or methotrexate, dactinomycin, and chlorambucil have also been used.

6. Protocols
Lymphomas
The usual dosage of methotrexate for the treatment of stages I or II of Burkitt’s lymphoma is 10–25 mg/day orally for 4–8 days.
Methotrexate is commonly given concomitantly with other antineoplastic agents in the treatment of stage III Burkitt’s lymphoma and lymphosarcomas.
In all stages, several courses of drug therapy are usually administered interposed with 7- to 10-day rest periods. Stage III lymphosarcomas may respond to combined drug therapy with methotrexate given in doses of 0.625–2.5 mg/kg daily.
Mycosis Fungoides
Clinical response occurs in up to 50% of patients receiving single-agent therapy with methotrexate for mycosis fungoides (cutaneous T-cell lymphoma).
In early stages of the disease, the usual dosage is 5–50 mg orally once weekly. The need for dosage reduction or discontinuance of therapy is determined by response to therapy and hematologic monitoring.
Methotrexate also has been administered twice weekly in doses of 15–37.5 mg in patients with disease that has responded poorly to once-weekly dosing.
In patients with advanced stages of mycosis fungoides, combination chemotherapy regimens that include IV methotrexate in higher doses followed by leucovorin rescue have been used.

7. Protocols Breast Cancer
One commonly employed regimen (CMF) for the treatment of early breast cancer includes a methotrexate dosage of 40 mg/m2 (administered IV) on days 1 and 8 of each cycle combined with cyclophosphamide 100 mg/m2 on days 1 through 14 of each cycle and fluorouracil 600 mg/m2 on days 1 and 8 of each cycle.
Cycles generally were repeated monthly (i.e., allowing a 2-week rest period between cycles) for a total of 6–12 cycles.
Dosage was reduced In patients older than 60 years of age & if myelosuppression developed.
There is some evidence that the addition of doxorubicin to a regimen of cyclophosphamide, methotrexate, and fluorouracil can improve outcome further in patients with early breast cancer and more than 3 positive axillary lymph nodes.

8. Administration
Great care should be taken to prevent inhaling particles of the chemical and exposing the skin to it.

10. Methotrexate formulations or diluents containing preservatives (benzyl alcohol) must not be used for intrathecal administration or high-dose methotrexate therapy.

11. Guidelines for parenteral administration of intermediate- or high-dose methotrexate (HDMTX)
500mg/m2 over <4hrs or 1gm/m2 over >4hrs
Prior to MTX administration the following laboratory parameters should be confirmed:
WBCs > 1500/mm3
Platelets > 75,000/mm3
Neutrophils > 200/mm3
IV ID (intermediate dose) methotrexate is1g/m2, HD (high dose) is 2.5g/m2,
the presence of pleural effusions or ascites can substantially alter the disposition of the drug (see Pharmacokinetics: Elimination). Slow release of methotrexate from third space accumulations may prolong the terminal half-life and may increase the risk of drug toxicity with high doses (i.e., exceeding 250 mg/m2).
Vd approximately total body water
Methotrexate is retained for several weeks in the kidneys and for months in the liver.
s.bilirubin<1.2mg/dl
SGPT (ALT)<450 U
Normal s. Cr.
Creatinine clearance>60ml/min
Previous mucositis should be healed
& pleural effusions should be drained prior to MTX administration

12. Hydration, Urine alkalinization & Leucoverin rescue
Administer 1 L/m2 of IV fluids over 6 hrs prior to initiation of MTX infusion. Continue hydration at 125ml/m2/hr (3 L/m2 daily) during the MTX infusion & for 2 days after the infusion has been completed.
Urine should be alkalinized using sodium bicarbonate. Alkalinize urine to maintain the urine pH >7 during the MTX infusion & leucoverin therapy. Alkalinization may be either orally or by incorporating sodium bicarbonate in the IV fluids
Leucovorin rescue required for MTX doses >500mg/m2, & considered for MTX doses mg/m2 for ALL, Breast CA, head/neck CA lung CA, osteosarcoma, non hodgkin’s lymphoma, others
Leucoverin dose 15 mg/m2 every 6 hours for 12 doses was begun at the end of the MTX infusion
hydration and urinary alkalinization may be needed to prevent precipitation of the drug and/or its metabolites in the renal tubules.
Leucovorin a potent folic acid antagonist antidote (folinic acid )

14. IV Administration
Reconstitution. Reconstitute lyophilized powder for injection immediately before use with a sterile, preservative-free solution (e.g., 5% dextrose injection, 0.9% sodium chloride injection)
Reconstitute 20 mg vial to a concentration ≤25 mg/mL Reconstitute 1 g vial with 19.4 mL of appropriate solution to yield a concentration of 50 mg/mL.
Dilution. When high doses are administered by IV infusion, dilute total dose of reconstituted solution in 5% dextrose injection.
May further dilute commercially available solution for IV injection containing preservatives with a compatible solution (e.g., 0.9% sodium chloride injection).
Preservative-free solutions may be diluted immediately prior to use with an appropriate sterile, preservative-free solution (e.g., 5% dextrose injection, 0.9% sodium chloride injection)

15. Stability
Methotrexate sodium injection and powder for injection should be protected from light and stored at 15–30°C.
Compatible with:
Dextrose 5% in water
Sodium chloride 0.9%
Maximum reported stability periods:
In D5W- 10 days at room temperature and 30 days refrigerated protected from light.
In NS- 7 days at room temperature and 105 days refrigerated protected from light.
Storage of solutions containing preservatives after further dilution for 24 hours at 21–25°C results in a product within 90% of label potency.
Use preservative-free solution immediately after further dilution

16. Intrathecal Administration
Reconstitution. For intrathecal injection, reconstitute lyophilized powder to a concentration of 1 mg/mL with an appropriate sterile preservative-free diluent (e.g., 0.9% sodium chloride injection).
Dilution. For intrathecal injection, dilute methotrexate preservative-free solution for injection to a concentration of 1 mg/mL with an appropriate sterile preservative-free diluent (e.g., 0.9% sodium chloride injection).

17. Adverse drug reactions
Dermatologic and Sensitivity Reactions.
Severe, occasionally fatal cutaneous or sensitivity reactions e.g.,
Toxic epidermal necrolysis
Stevens-Johnson syndrome
Exfoliative dermatitis
Skin necrosis
Erythema multiforme
reported in pediatric and adult patients within days of receiving drug at various dosages, by various routes, and for various conditions.
Erythematous rashes, pruritus, dermatitis, urticaria, folliculitis, photosensitivity, depigmentation, hyperpigmentation, petechiae, ecchymoses, telangiectasia, acne, furunculosis, and skin ulceration also reported.

18. Hematologic Effects Monitoring Management
Suppressed hematopoiesis:
Anemia
Aplastic anemia
Pancytopenia
Leukopenia
Neutropenia
Thrombocytopenia.
Perform CBCs, including differential and platelet counts, at least weekly in patients with neoplastic disease
Management
Since potentially fatal opportunistic infections (e.g., Pneumocystis carinii pneumonia) have been reported in patients receiving methotrexate therapy, the possibility of P. carinii pneumonia should be considered in patients who develop pulmonary symptoms. In addition, pulmonary function tests may be useful if methotrexate-induced pulmonary toxicity is suspected, particularly if baseline values are available.
If profound leukopenia and fever occur, observe patient closely and initiate broad-spectrum antibiotic therapy if there are signs of infection.
Blood or platelet transfusions may be necessary in patients with severe myelosuppression.

19. Management Prevention Monitoring Nephrotoxicity
May cause renal damage that may lead to acute renal failure.
Nephrotoxicity is due principally to precipitation of methotrexate and 7-hydroxymethotrexate in the renal tubules.
Careful attention to renal function including:
Adequate hydration
Urine alkalinization
Measurement of methotrexate and Scr concentrations is essential.
Scr must be normal and Clcr >60 ml/min before therapy initiation.
Repeat Scr and serum methotrexate 24 hours after starting methotrexate and at least once daily until the methotrexate concentration is <0.023 mcg/mL (0.05 mcM).
Management
Allopurinol monitor CBC inc myelosuppression
If renal impairment develops during methotrexate therapy, dosage should be reduced or the drug discontinued until renal function is improved or restored.
Institute appropriate corrective measures (e.g., use of leucovorin calcium, acute intermittent hemodialysis with a high-flux dialyzer).
In addition, tumor lysis syndrome associated with other cytotoxic drugs (e.g., fludarabine, cladribine) also has been reported in patients with rapidly growing tumors who were receiving methotrexate.

20. Dose adjustment in renal impairment
Cr Cl ml/min
Decrease dose 25%
Cr Cl ml/min
Decrease dose 33%
Cr Cl ml/min
Decrease dose 50-70%
Cr Cl < 10 ml/min
Avoid use HD
Give 50% dose as supplement
CAPD
No supplement

21. Management Monitoring Hepatotoxicity Liver function tests at baseline.
Abnormal liver function test results frequently occur 1–2 days following a dose of methotrexate, and it is recommended that liver function tests be performed at least 1 week after the last dose of the drug. Because these tests generally return to normal within a few days.
Liver biopsy is currently the only reliable measure of hepatotoxicity.
Possible hepatotoxicity; may be acute (increased serum aminotransferase concentrations) or chronic (fibrosis and cirrhosis).
Management
Chronic hepatotoxicity, potentially fatal, generally occurs after prolonged use (≥2 years) and after a total dose of ≥1.5 g
Liver function test results should generally return to normal within 1–2 weeks following discontinuance of the drug
If substantial abnormal liver function test results develop and persist, methotrexate therapy should be withheld for 1–2 weeks and liver function tests repeated. However, if substantial abnormal liver function test results persist, a liver biopsy is recommended.

22. Dose adjustment in hepatic impairment
s.bilirubin 4-5mg/dl
Decrease dose 25%
s.bilirubin >5mg/dl
Omit
ALT <180
ALT>450 U/L

23. Management Pulmonary toxicity Monitoring
Potentially fatal pulmonary toxicity; can progress rapidly and may not be fully reversible.
Adverse pulmonary effects (i.e., acute or chronic interstitial pneumonitis, pulmonary fibrosis) may occur at any dosage at any time during therapy.
Frequently Chest radiographs should be performed
If manifestations (e.g., fever, cough [especially dry and nonproductive), dyspnea, chest pain, hypoxemia [possibly severe], radiographic evidence of pulmonary infiltrates [usually diffuse and/or alveolar]) occur, discontinue and carefully evaluate, including exclusion of possible infectious causes.
Since potentially fatal opportunistic infections (e.g., Pneumocystis carinii pneumonia) have been reported in patients receiving methotrexate therapy, the possibility of P. carinii pneumonia should be considered in patients who develop pulmonary symptoms. In addition, pulmonary function tests may be useful if methotrexate-induced pulmonary toxicity is suspected, particularly if baseline values are available.
Management
Management is mainly supportive and may include mechanical ventilation.

24. GI Effects. Management Vomiting Diarrhea Ulcerative Stomatitis
Discontinue drug until recovery otherwise intestinal perforation may lead to hemorrhagic enteritis & death.
Previous mucositis should be healed
Use with extreme caution in presence of peptic ulcer disease or ulcerative colitis.

25. Drug Interactions

26. Pharmacodynamic Interactions
Additive Adverse Drug effect:
Hepatotoxic Agents (retinoids, azathioprine, sulfasalazine)
Increase in adverse hepatic effects expected.
Nephrotoxic Drugs
Possible altered renal elimination of methotrexate.
Completely contraindicated with live vaccines >2 weeks before or > 3months after chemotherapy
Methotrexate/Asparaginase
The exact mechanism of the interaction is unknown and may be a combination of mechanisms. Asparaginase has been shown to decrease the cellular uptake of methotrexate.
24-96hrs
The optimal time interval between asparaginase and a subsequent dose of methotrexate has been shown to be 9-10 days. A 24-hour interval between methotrexate and a subsequent dose of asparaginase allows for the return of methotrexate's effects on malignant cells
Action required:
Close monitoring of
LFTs & renal function

27. Pharmacokinetic Interactions
MTX cause damage of GIT
Reduce absorption of Verapamil & Phenytoin by 20-35% and so loss of therapeutic effect.
MTX is also displaced from protein binding sites by:
Salicylates
Co-trimoxazole(sulfonamides)
Sulfonylureas, phenytoin, phenylbutazone, tetracyclines, chloramphenicol, and aminobenzoic acid resulting in increased free methotrexate concentrations.
While basic drugs are largely bound to acid α1- glycoprotein in plasma, acidic drugs are bound on the albumin molecule (e.g. warfarin)
since MTX is a weak acid, it is displaced from protein binding sites by weak acids % protein bound
CYP 450

28. Pharmacokinetic Interactions
MTX may decrease clearance of theophylline
Monitor
theophylline
level
Salicylates & NSAIDs can cause severe, possibly fatal MTX toxicity including hematologic and GI toxicity ( HD-MTX) either by competition with MTX for active tubular secretion & delay of elimination or by decreasing renal perfusion (due to inhibition of PG synthesis (PD interaction).
Concomitant use of penicillins (e.g., amoxicillin, carbenicillin) may decrease renal clearance of methotrexate, presumably by inhibiting renal tubular secretion of the drug & thus increase serum concentrations of methotrexate, resulting in GI or hematologic toxicity
CYP 450
There are separate active transport systems for acidic and basic drugs in the proximal tubule and competition for the active transport systems can be expected to occur between drugs secreted by the acidic system and those secreted by the basic system.
Action required:
NSAIDs should be avoided in patients receiving HD -MTX
Action required:
Close monitoring

29. Resistance to methotrexate
Due to:
Decreased cellular uptake of the drug
Increased dihydrofolate reductase activity (associated with increased synthesis of the enzyme)
Decreased binding of methotrexate to dihydrofolate reductase (because of mutated dihydrofolate reductase protein)
Decreased intracellular concentrations of polyglutamylated metabolites of methotrexate
However, the precise mechanism of this resistance development has not been established.
Methotrexate is actively transported across cell membranes by folate carrier & folate receptor. At serum methotrexate concentrations exceeding 0.1 mcmol/mL, passive diffusion becomes a major means of intracellular transport of the drug.

30. References AHFS detailed monograph 2009
AHFS drug information, Dosing Companion 2004
Epocrates 2008
Clinical pharmacology 2001
Trissel’s™ 2 Clinical Pharmaceutics Database 2009