Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PEMETREXED DITROMETHAMINE vs PEMETREXED DISODIUM
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Pemetrexed inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), enzymes involved in folate-dependent purine and pyrimidine synthesis, leading to disruption of DNA synthesis and cell death.
Pemetrexed is a folate analog metabolic inhibitor that disrupts folate-dependent metabolic processes essential for cell replication. It inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), thereby inhibiting de novo synthesis of thymidine and purine nucleotides.
FDA-approved: In combination with cisplatin for initial treatment of patients with malignant pleural mesothelioma who are unresectable or not surgical candidates.,FDA-approved: As a single agent for locally advanced or metastatic non-small cell lung cancer (NSCLC) after prior platinum-based chemotherapy.,FDA-approved: In combination with pembrolizumab and platinum chemotherapy for first-line treatment of metastatic non-squamous NSCLC.,Off-label: Treatment of recurrent or metastatic cervical cancer, breast cancer, bladder cancer, colorectal cancer, and others.
Mesothelioma: In combination with cisplatin for treatment of malignant pleural mesothelioma in patients who are not candidates for curative surgery.,Non-small cell lung cancer: First-line treatment in combination with cisplatin for locally advanced or metastatic nonsquamous NSCLC.,Non-small cell lung cancer: Maintenance monotherapy for locally advanced or metastatic nonsquamous NSCLC with stable disease after 4 cycles of platinum-based chemotherapy.,Non-small cell lung cancer: Second-line treatment as monotherapy for locally advanced or metastatic nonsquamous NSCLC after prior chemotherapy.
500 mg/m2 intravenously over 10 minutes every 21 days.
500 mg/m2 intravenously over 10 minutes on Day 1 of each 21-day cycle, with vitamin B12 and folic acid supplementation.
Terminal half-life 3.5 hours (range 2.5-5.0 hours) in patients with normal renal function; prolonged to 5-10 hours in moderate renal impairment. Clinical context: Half-life is dose-independent; clearance correlates with creatinine clearance.
Terminal half-life is 3.5 hours in patients with normal renal function. Increases in renal impairment (up to 20 hours if Cr Cl <45 m L/min).
Pemetrexed is primarily excreted unchanged in the urine. It undergoes minimal hepatic metabolism; less than 5% is metabolized by the liver.
Pemetrexed is primarily eliminated unchanged in urine. It undergoes minimal hepatic metabolism. The drug is a substrate for multidrug resistance-associated proteins (MRPs) and possibly other transporters.
Primarily renal excretion: 70-90% of the dose is eliminated unchanged in urine within 24 hours. Fecal excretion accounts for <5%.
Primarily renal excretion (70-90% as unchanged drug within 24 hours). Biliary/fecal excretion accounts for <5%.
81% bound primarily to albumin; minimal binding to alpha-1-acid glycoprotein.
~81% bound primarily to albumin.
Vd at steady state = 16.1 L/m² (approximately 0.4 L/kg in adults). Clinical meaning: Indicates distribution into total body water with limited tissue binding; low Vd suggests minimal extravascular distribution.
Vd = 0.2 L/kg (approximately 16 L in adults). Indicates limited distribution to extravascular spaces.
Intravenous only; bioavailability is 100% by IV route. Not orally available due to poor absorption and extensive first-pass metabolism.
Intravenous: 100% (only route of administration).
Cr Cl ≥45 m L/min: 500 mg/m2; Cr Cl 30-44 m L/min: 375 mg/m2; Cr Cl <30 m L/min: not recommended.
Cr Cl ≥45 m L/min: No adjustment. Cr Cl <45 m L/min: Not recommended. For Cr Cl 40-59 m L/min, no adjustment; Cr Cl <40 m L/min, not recommended based on clinical trial criteria.
No dose adjustment recommended for Child-Pugh A or B. Child-Pugh C: no data.
No specific dose adjustment guidelines for hepatic impairment. Use caution with bilirubin >1.5 times ULN and/or AST/ALT >3 times ULN. Child-Pugh classification not formally studied.
Not established; safety and efficacy not determined in pediatric patients.
Safety and efficacy not established in pediatric patients. No recommended dosing.
No specific dose adjustment; monitor renal function closely due to age-related decline in Cr Cl.
No specific dose adjustment recommended based on age alone. Monitor renal function closely as elderly patients may have reduced Cr Cl.
Pemetrexed can cause severe or fatal hypersensitivity reactions, including anaphylaxis. It also causes severe myelosuppression, which may require dose modification or discontinuation. Patients must be pretreated with corticosteroids and vitamin supplementation to reduce toxicity.
Pemetrexed can cause severe myelosuppression, which may lead to infection and bleeding. Patients must be monitored for bone marrow suppression. Adequate folic acid and vitamin B12 supplementation is required to reduce toxicity.
Myelosuppression: Dose-dependent, monitor blood counts regularly.,Renal toxicity: Excreted renally; adjust dose in renal impairment (Cr Cl <45 m L/min).,Gastrointestinal toxicity: Nausea, vomiting, diarrhea; may require antiemetics.,Hypersensitivity reactions: Premedicate with corticosteroids.,Folic acid and vitamin B12 deficiency: Supplement to reduce hematologic toxicity.,Third-space fluid accumulation: Consider drainage before treatment.
Bone marrow suppression: Monitor blood counts regularly; dose adjust or hold for severe neutropenia, thrombocytopenia, or anemia.,Renal toxicity: Avoid in creatinine clearance <45 m L/min; monitor renal function.,Gastrointestinal toxicity: Severe diarrhea, mucositis may occur; manage with supportive care.,Dermatologic toxicity: Severe rash may occur; premedicate with corticosteroids.,Radiation recall: Risk of severe radiation recall in patients who have received prior radiotherapy.,Folic acid and vitamin B12 supplementation: Required to reduce hematologic and gastrointestinal toxicity.,Pregnancy: Can cause fetal harm; advise women of reproductive potential to use effective contraception.
History of severe hypersensitivity reaction to pemetrexed or any excipients.,Concurrent yellow fever vaccine (risk of systemic fatal disease).,Severe renal impairment (Cr Cl <45 m L/min) not meeting criteria for dose adjustment.
History of severe hypersensitivity reaction to pemetrexed or any excipient.,Patients with creatinine clearance <45 m L/min (contraindicated for use in combination with cisplatin due to increased toxicity).
No specific dietary restrictions. However, folic acid supplements and vitamin B12 are required. Avoid folic acid antagonists like methotrexate.
No known food interactions. Avoid folic acid-containing supplements beyond prescribed dose as they may interfere with pemetrexed activity. Maintain adequate hydration.
Pemetrexed is a folate analog metabolic inhibitor that is teratogenic in animals. In humans, it is contraindicated in pregnancy due to its mechanism of action interfering with DNA synthesis and cell division. First trimester exposure carries the highest risk of major congenital malformations (e.g., neural tube defects, craniofacial anomalies). Second and third trimester exposure may cause fetal growth restriction, oligohydramnios, and potential fetal demise. Use in pregnant women is not recommended unless no safer alternative exists.
Pemetrexed is contraindicated in pregnancy. It is an antifolate antimetabolite that inhibits thymidylate synthase and other folate-dependent enzymes, essential for DNA synthesis and cell division. Based on its mechanism of action and animal studies, it is expected to cause fetal harm when administered to a pregnant woman. First trimester: High risk of teratogenicity (neural tube defects, craniofacial, cardiovascular malformations) due to folate antagonism. Second and third trimesters: Risk of fetal growth restriction, oligohydramnios, and fetal death. Embryofetal toxicity and teratogenicity have been demonstrated in mice and rats at doses lower than the human therapeutic dose.
There are no data on the presence of pemetrexed in human milk, its effects on the breastfed infant, or milk production. Due to the potential for serious adverse reactions in nursing infants (e.g., myelosuppression, gastrointestinal toxicity), breastfeeding is not recommended during pemetrexed therapy and for at least one week after the last dose. The M/P ratio is unknown.
No data available on the presence of pemetrexed in human milk, its effects on the breastfed infant, or on milk production. Due to the potential for serious adverse reactions in the breastfed infant (including myelosuppression, gastrointestinal toxicity, and carcinogenesis), breastfeeding is not recommended during therapy and for at least 1 week after the last dose. The M/P ratio is unknown.
No specific dosing adjustments for pregnancy are established due to lack of data. Physiologic changes in pregnancy (increased renal clearance, expanded plasma volume) may reduce drug exposure, but dose increases are not recommended due to potential fetal toxicity. In animal studies, lower doses produced embryotoxicity. Therefore, dose adjustments should not be made; the drug should be avoided in pregnancy.
No specific dose adjustment guidelines exist for pemetrexed in pregnancy because its use is contraindicated. However, pregnancy may alter the pharmacokinetics of pemetrexed due to increased renal clearance (increased glomerular filtration rate) and expanded plasma volume, potentially reducing drug exposure. No formal studies have been conducted. Given the high risk of fetal harm, pemetrexed should not be used in pregnant women. If treatment is deemed necessary for a life-threatening condition, the risks versus benefits must be considered, and dosing adjustments cannot be recommended due to lack of data.
Administer folic acid and vitamin B12 supplementation to reduce toxicity. Premedicate with corticosteroids to prevent rash. Monitor renal function; dose adjust for Cr Cl <45 m L/min. Avoid NSAIDs for 2 days before and after dose. Ensure adequate hydration. Do not mix with calcium-containing solutions.
Administer folic acid 350-1000 mcg orally daily beginning 7 days before first dose and continuing throughout therapy. Administer vitamin B12 1000 mcg IM 1 week before first dose and every 3 cycles thereafter. Premedicate with dexamethasone 4 mg orally twice daily the day before, day of, and day after each dose to reduce cutaneous reactions. Monitor for myelosuppression, especially neutropenia; dose reduce as needed. Contraindicated in patients with creatinine clearance <45 m L/min. Avoid NSAIDs 2-5 days before and 2 days after pemetrexed due to increased toxicity.
Take folic acid daily and vitamin B12 injections every 9 weeks as prescribed.,Inform all healthcare providers about your treatment; avoid NSAIDs like ibuprofen or naproxen.,Report new or worsening rash, diarrhea, or mouth sores immediately.,Drink plenty of fluids to stay hydrated.,Avoid receiving live vaccines during treatment.
Take folic acid supplements daily, starting 7 days before your first treatment and continuing until your doctor stops it.,You will receive vitamin B12 injections before your first dose and then every 9 weeks.,Take a steroid medication (dexamethasone) as prescribed the day before, day of, and day after each infusion to prevent skin reactions.,Avoid taking NSAIDs (like ibuprofen or naproxen) for at least 2-5 days before and 2 days after your pemetrexed infusion.,Report any signs of infection (fever, chills, sore throat), unusual bleeding or bruising, or severe fatigue immediately.,Drink plenty of fluids unless otherwise instructed. There are no specific dietary restrictions, but maintain a balanced diet.,Use effective contraception during treatment and for at least 6 months after the last dose (females) or 3 months (males). Do not breastfeed during treatment.
"Methotrimeprazine may reduce the gastrointestinal absorption of tromethamine, an alkalinizing agent, leading to decreased systemic exposure and potentially diminished therapeutic efficacy. This interaction is hypothesized to occur via altered gastric pH or motility, though direct evidence is limited. Patients may experience reduced effectiveness of tromethamine in managing acid-base disorders."
"Tromethamine, an alkalinizing agent used to correct metabolic acidosis, can increase gastric pH, which may reduce the absorption of weakly acidic drugs like estrone sulfate. This altered gastrointestinal environment can decrease estrone sulfate bioavailability, potentially compromising its systemic effects for hormone replacement therapy. Clinically, this may lead to reduced efficacy of estrone sulfate, requiring dose adjustments or alternative administration routes."
"Tromethamine, an alkalinizing agent, can increase urinary pH, which enhances the renal excretion of sotalol, a class III antiarrhythmic that is primarily eliminated unchanged by the kidneys. This interaction may lead to reduced serum sotalol concentrations, potentially decreasing its therapeutic efficacy and increasing the risk of arrhythmia recurrence, particularly in patients with renal impairment or those requiring precise antiarrhythmic control."
"The risk or severity of adverse effects can be increased when Pemetrexed is combined with Leflunomide."
"Pemetrexed may decrease the cardiotoxic activities of Acetyldigitoxin."
"Pemetrexed may increase the immunosuppressive activities of Fingolimod."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about PEMETREXED DITROMETHAMINE vs PEMETREXED DISODIUM, answered by our medical review team.
PEMETREXED DITROMETHAMINE is a Antineoplastic Antifolate that works by Pemetrexed inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), enzymes involved in folate-dependent purine and pyrimidine synthesis, leading to disruption of DNA synthesis and cell death.. PEMETREXED DISODIUM is a Antineoplastic Antifolate that works by Pemetrexed is a folate analog metabolic inhibitor that disrupts folate-dependent metabolic processes essential for cell replication. It inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), thereby inhibiting de novo synthesis of thymidine and purine nucleotides.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PEMETREXED DITROMETHAMINE and PEMETREXED DISODIUM depend on the specific clinical indication. These are both Antineoplastic Antifolate agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of PEMETREXED DITROMETHAMINE is: 500 mg/m2 intravenously over 10 minutes every 21 days.. The standard adult dose of PEMETREXED DISODIUM is: 500 mg/m2 intravenously over 10 minutes on Day 1 of each 21-day cycle, with vitamin B12 and folic acid supplementation.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between PEMETREXED DITROMETHAMINE and PEMETREXED DISODIUM in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. PEMETREXED DITROMETHAMINE is classified as Category C. Pemetrexed is a folate analog metabolic inhibitor that is teratogenic in animals. In humans, it is contraindicated in pregnancy due to its mechanism of action interfering with DNA . PEMETREXED DISODIUM is classified as Category C. Pemetrexed is contraindicated in pregnancy. It is an antifolate antimetabolite that inhibits thymidylate synthase and other folate-dependent enzymes, essential for DNA synthesis an. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.