Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PEMETREXED vs PEMETREXED FOR INJECTION
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
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), leading to inhibition of de novo purine and pyrimidine synthesis.
Pemetrexed is a folate analog metabolic inhibitor that inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), enzymes involved in folate-dependent de novo synthesis of thymidine and purine nucleotides, thereby disrupting DNA and RNA synthesis.
Malignant pleural mesothelioma (in combination with cisplatin),Non-small cell lung cancer (NSCLC) - first-line treatment (in combination with cisplatin),NSCLC - maintenance therapy (after platinum-based chemotherapy),NSCLC - second-line treatment (single agent)
Malignant pleural mesothelioma in combination with cisplatin for unresectable or patients who are not candidates for curative surgery,Non-small cell lung cancer (NSCLC), first-line treatment in combination with cisplatin for nonsquamous histology,NSCLC maintenance therapy for nonsquamous histology after platinum-based therapy,NSCLC second-line treatment for nonsquamous histology
500 mg/m2 IV over 10 minutes on Day 1 of each 21-day cycle, with folic acid and vitamin B12 supplementation.
500 mg/m² IV over 10 minutes on Day 1 of each 21-day cycle, in combination with cisplatin 75 mg/m² IV over 2 hours starting 30 minutes after pemetrexed completion. Administer folic acid 350-1000 µg po daily starting 7 days before first dose and continuing until 21 days after last dose, vitamin B12 1000 µg IM 7 days before first dose and every 3 cycles thereafter, and dexamethasone 4 mg po twice daily on day before, day of, and day after pemetrexed.
Terminal half-life is approximately 3.5 hours in patients with normal renal function (creatinine clearance ≥60 m L/min). Clinically, half-life is prolonged in renal impairment (up to 20 hours in severe impairment), requiring dose adjustment.
The terminal elimination half-life is approximately 3-4 hours in patients with normal renal function (creatinine clearance ≥90 m L/min). In patients with impaired renal function (creatinine clearance 45-79 m L/min), the half-life may be prolonged to 4-5 hours.
Pemetrexed is primarily eliminated unchanged in the urine. It undergoes minimal hepatic metabolism. Renal excretion accounts for approximately 70-90% of elimination.
Pemetrexed is minimally metabolized; it is primarily excreted unchanged in urine via active tubular secretion and glomerular filtration. No significant hepatic metabolism. Enzymes: not extensively metabolized by CYP450.
Primarily eliminated unchanged in urine (70-90% of dose via renal excretion over 24 hours); minimal biliary/fecal excretion (<5%).
Approximately 70-90% of the administered dose is excreted unchanged in the urine within 24 hours. Renal elimination is the primary route, with negligible biliary or fecal excretion (<5%).
Approximately 81% bound to plasma proteins, primarily albumin (given its structure as a folate analog).
Approximately 81-88% bound to plasma proteins, primarily albumin.
Volume of distribution is about 16.1 L/m² (total body water); in weight-based terms ~0.3-0.4 L/kg, indicating limited tissue distribution consistent with a polar molecule.
The volume of distribution at steady state is approximately 16.1 L/m² (or roughly 0.4 L/kg based on average body surface area). This low value suggests limited extravascular distribution, consistent with a hydrophilic drug.
Only administered intravenously; oral bioavailability is negligible (<1%) due to poor intestinal absorption and first-pass metabolism, thus no oral formulation available.
Pemetrexed is administered only intravenously; oral bioavailability is not applicable (0% due to lack of oral formulation).
Cr Cl ≥45 m L/min: no adjustment. Cr Cl <45 m L/min: not recommended; consider dose reduction to 500 mg/m2 if Cr Cl 40–45 m L/min with close monitoring; do not use if Cr Cl <40 m L/min.
Cr Cl ≥45 m L/min: No dose adjustment. Cr Cl <45 m L/min: Contraindicated; do not administer. For Cr Cl between 40-79 m L/min, consider dose reduction to 400 mg/m² if prior grade 3/4 toxicity. Monitor Cr Cl prior to each cycle.
Child-Pugh A and B: no adjustment. Child-Pugh C: insufficient data; use with caution.
Child-Pugh Class A or B: No recommended dose adjustment. Class C: No data; use with caution. Bilirubin >5 times ULN: Avoid use. AST/ALT >5 times ULN: Consider dose reduction to 400 mg/m² if severe transaminase elevation with bilirubin >3 times ULN.
Not FDA approved; limited data: 500 mg/m2 IV over 10 minutes Day 1 every 21 days, with folic acid and B12 supplementation, based on adult protocol. Weight-based for patients <1.5 m²: calculate BSA and dose accordingly.
Safety and efficacy not established in pediatric patients. No recommended dose.
No specific dose adjustment; monitor renal function (Cr Cl) due to age-related decline; ensure folic acid and vitamin B12 supplementation.
No dose adjustment based on age alone. Monitor renal function (Cr Cl) closely; elderly more likely to have decreased Cr Cl and require dose reduction or discontinuation per renal adjustment criteria. Evaluate for increased risk of myelosuppression and fatigue.
Pemetrexed can cause severe and sometimes fatal myelosuppression, renal failure, and severe gastrointestinal toxicity. Patients must be pretreated with corticosteroids and folic acid and vitamin B12 to reduce toxicity.
Pemetrexed can cause severe myelosuppression, including severe neutropenia, anemia, and thrombocytopenia. Fatalities have been reported. Patients must have absolute neutrophil count (ANC) ≥1500 cells/mm³ and platelet count ≥100,000 cells/mm³ prior to initiation. Dose reduction or delay is required based on nadir counts.
Bone marrow suppression (including neutropenia, thrombocytopenia, anemia); renal toxicity (monitor renal function); gastrointestinal toxicity (e.g., diarrhea, mucositis); dermatologic reactions (e.g., rash, exfoliation); radiation recall reactions; increased risk of toxicity in patients with pleural effusion or ascites (consider drainage); embryo-fetal toxicity.
Bone marrow suppression (dose-dependent); renal toxicity (requires adequate renal function, Cr Cl ≥45 m L/min); gastrointestinal toxicity (nausea, vomiting, mucositis); dermatologic reactions (rash, desquamation); radiation recall; requires folic acid and vitamin B12 supplementation to reduce toxicity; pregnancy category D; fetal harm; hypersensitivity reactions.
History of severe hypersensitivity reaction to pemetrexed; concomitant administration of yellow fever vaccine; severe renal impairment (creatinine clearance <45 m L/min) (relative contraindication due to increased toxicity).
History of severe hypersensitivity reaction to pemetrexed; Cr Cl <45 m L/min for patients with mesothelioma receiving cisplatin; concurrent yellow fever vaccine (live attenuated).
No specific food interactions are documented. However, patients should maintain adequate folic acid intake through diet and supplements as prescribed. Avoid grapefruit or grapefruit juice? There is no known interaction with grapefruit. Patients should maintain a balanced diet and avoid alcohol to prevent liver stress.
No specific dietary restrictions. However, vitamin B12 (from animal products) and folic acid (from leafy greens) are essential supplements. Avoid high-folate foods only if advised by physician (unlikely, as supplementation is required).
Pemetrexed is a folate analog antimetabolite that inhibits thymidylate synthase, dihydrofolate reductase, and glycinamide ribonucleotide formyltransferase. It is teratogenic in animal studies at doses below the recommended human dose. In humans, there are no adequate studies in pregnant women; however, based on its mechanism of action, there is potential for fetal harm. First trimester exposure carries the highest risk for major congenital malformations (neural tube, cardiac, skeletal defects). Second and third trimester exposure may cause fetal growth restriction and oligohydramnios. Late pregnancy administration may cause neonatal myelosuppression and toxicity.
Pemetrexed is teratogenic and embryotoxic in animal studies. In humans, it is contraindicated in pregnancy (FDA Pregnancy Category D). First trimester exposure carries high risk of major congenital malformations, spontaneous abortion, and fetal death. Second and third trimester exposure increases risk of intrauterine growth restriction, oligohydramnios, and fetal myelosuppression.
No human data on excretion into breast milk. Pemetrexed is a small molecule (molecular weight 427.46 g/mol) with low protein binding (~81%) and a terminal half-life of 3.5 hours; it is likely excreted into milk. M/P ratio unknown. Due to potential for serious adverse reactions (myelosuppression, gastrointestinal toxicity), breastfeeding is contraindicated during therapy and for at least 1 week after last dose.
No data on pemetrexed excretion in human milk. Due to potential for serious adverse reactions in nursing infants (e.g., myelosuppression, gastrointestinal toxicity), breastfeeding is contraindicated during treatment and for at least 1 week after last dose. M/P ratio not established.
No established dosing guidelines for pregnancy. Physiologic changes (increased renal blood flow, volume of distribution) may reduce pemetrexed exposure, but dose adjustments are not recommended due to lack of safety data. Use only if clearly needed and risk of maternal toxicity outweighs fetal risks. Avoid in first trimester.
No established dosing guidelines in pregnancy due to contraindication. Pharmacokinetic changes in pregnancy (increased plasma volume, renal clearance) may reduce drug exposure, but dose adjustments are not recommended because of teratogenicity and lack of safety data. Treatment should be avoided or pregnancy terminated if exposure occurs.
Pemetrexed requires vitamin B12 and folate supplementation to reduce hematologic and gastrointestinal toxicity. Administer folic acid daily (350-1000 mcg) starting 7 days before first dose and continue for 21 days after last dose. Vitamin B12 (1000 mcg IM) should be given 1 week before first dose and repeated every 3 cycles. Contraindicated in patients with creatinine clearance <45 m L/min; dose reduction required for moderate renal impairment. Monitor for severe cutaneous reactions (Stevens-Johnson syndrome) and interstitial pneumonitis. Premedicate with dexamethasone (4 mg PO BID) on the day before, day of, and day after pemetrexed to reduce skin rash incidence.
Pemetrexed requires folic acid and vitamin B12 supplementation to reduce hematologic and gastrointestinal toxicity. Administer dexamethasone prophylaxis to prevent skin rash. Contraindicated in patients with creatinine clearance <45 m L/min. Avoid concurrent NSAIDs in patients with mild to moderate renal impairment (Cr Cl 45-79 m L/min) as they may increase pemetrexed toxicity.
Take folic acid daily as prescribed, starting 7 days before your first treatment and continuing for 21 days after the last dose.,You will receive a vitamin B12 injection once every three treatment cycles, beginning 1 week before the first dose.,Report any new or worsening shortness of breath, cough, or fever immediately, as this may indicate lung inflammation.,Avoid nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or aspirin unless approved by your doctor, especially if you have kidney problems.,Use effective contraception during treatment and for 6 months after the last dose; male patients should avoid fathering a child.,Do not breastfeed while taking this medication.,Stay hydrated and inform your doctor if you experience severe diarrhea, vomiting, or signs of dehydration.,Limit sun exposure and use sunscreen, as pemetrexed may cause photosensitivity.
Take folic acid daily and vitamin B12 injections as prescribed to reduce side effects.,Report any skin rash, diarrhea, or mouth sores immediately.,Avoid aspirin and NSAIDs unless approved by your doctor, especially if you have kidney problems.,Stay hydrated and monitor for signs of infection (fever, chills).,Do not skip or stop your vitamin supplements even if you feel well.
"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."
"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 vs PEMETREXED FOR INJECTION, answered by our medical review team.
PEMETREXED 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), leading to inhibition of de novo purine and pyrimidine synthesis.. PEMETREXED FOR INJECTION is a Antineoplastic Antifolate that works by Pemetrexed is a folate analog metabolic inhibitor that inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), enzymes involved in folate-dependent de novo synthesis of thymidine and purine nucleotides, thereby disrupting DNA and RNA synthesis.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PEMETREXED and PEMETREXED FOR INJECTION 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 is: 500 mg/m2 IV over 10 minutes on Day 1 of each 21-day cycle, with folic acid and vitamin B12 supplementation.. The standard adult dose of PEMETREXED FOR INJECTION is: 500 mg/m² IV over 10 minutes on Day 1 of each 21-day cycle, in combination with cisplatin 75 mg/m² IV over 2 hours starting 30 minutes after pemetrexed completion. Administer folic acid 350-1000 µg po daily starting 7 days before first dose and continuing until 21 days after last dose, vitamin B12 1000 µg IM 7 days before first dose and every 3 cycles thereafter, and dexamethasone 4 mg po twice daily on day before, day of, and day after pemetrexed.. 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 and PEMETREXED FOR INJECTION 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 is classified as Category C. Pemetrexed is a folate analog antimetabolite that inhibits thymidylate synthase, dihydrofolate reductase, and glycinamide ribonucleotide formyltransferase. It is teratogenic in ani. PEMETREXED FOR INJECTION is classified as Category C. Pemetrexed is teratogenic and embryotoxic in animal studies. In humans, it is contraindicated in pregnancy (FDA Pregnancy Category D). First trimester exposure carries high risk of. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.