Reviewed on 5/24/2022

What Is Pemetrexed and How Does It Work?

Pemetrexed is a prescription medication used for treating the symptoms of Crohn’s disease, rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, spondyloarthritis, and plaque psoriasis.

  • Pemetrexed is available under the following different brand names: Alimta, Pemfexy

What Are Dosages of Pemetrexed?

Adult dosage

Injection, lyophilized powder for reconstitution

  • 100mg/vial (Alimta)
  • 500mg/vial (Alimta)

Injectable solution

  • 500mg/vial (Pemfexy)


Adult dosage

  • In combination with cisplatin: Pemetrexed 500 mg/m2 IV on Day 1 of each 21-day cycle until disease progression or unacceptable toxicity

Nonsquamous Non-Small Cell Lung Carcinoma

Adult dosage

  • Combination with pembrolizumab and platinum chemotherapy
  • Alimta only
    • In combination with pembrolizumab and platinum chemotherapy: Pemetrexed 500 mg/m2 IV on Day 1 of each 21-day cycle for 4 cycles  
    • Combination with cisplatin
  • Alimta, Pemfexy
    • In combination with cisplatin: Pemetrexed 500 mg/m2 IV on Day 1 of each 21-day cycle for up to 6 cycles in the absence of disease progression or unacceptable toxicity  
  • Single agent
  • Alimta, Pemfexy
    • 500 mg/m2 IV on Day 1 of each 21-day cycle  

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Are Side Effects Associated with Using Pemetrexed?

Common side effects of the Pemetrexed include:

  • tiredness,
  • shortness of breath,
  • loss of appetite,
  • weight loss,
  • nausea,
  • vomiting,
  • diarrhea, and
  • constipation.

Serious side effects of the Pemetrexed include:

  • hives,
  • difficulty breathing,
  • swelling of the face, lips, tongue, or throat,
  • little or no urination,
  • new or worsening cough,
  • fever,
  • trouble breathing,
  • swelling, redness, or blistering of skin that was treated with radiation in the past,
  • chills,
  • tiredness,
  • mouth sores,
  • skin sores,
  • easy bruising,
  • unusual bleeding,
  • pale skin,
  • cold hands and feet,
  • shortness of breath, and
  • lightheadedness

Rare side effects of the Pemetrexed include:

  • none 

This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Pemetrexed?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions or concerns.

What Are Warnings and Precautions for Pemetrexed?


  • History of severe hypersensitivity reaction to pemetrexed

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Pemetrexed?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Pemetrexed?”


  • Treatment can cause severe, and sometimes fatal, renal toxicity; determine creatinine clearance before each dose and periodically monitor renal function during treatment with the drug; withhold therapy in patients with a creatinine clearance of less than 45 mL/minute
  • Serious and sometimes fatal, bullous, blistering, and exfoliative skin toxicity, including cases suggestive of Stevens-Johnson Syndrome/Toxic epidermal necrolysis, can occur; permanently discontinue drug for severe and life-threatening bullous, blistering or exfoliating skin toxicity
  • Serious interstitial pneumonitis, including fatal cases, can occur with treatment; withhold drug for acute onset of new or progressive unexplained pulmonary symptoms such as dyspnea, cough, or fever pending diagnostic evaluation; if pneumonitis is confirmed, permanently discontinue therapy
  • Radiation recall can occur in patients who have received radiation weeks to years previously; monitor patients for inflammation or blistering in areas of previous radiation treatment; permanently discontinue therapy for signs of radiation recall
  • Based on findings from animal studies and its mechanism of action, therapy can cause fetal harm when administered to a pregnant woman; avoid pregnancy (see Pregnancy)
  • Myelosuppression
    • Therapy can cause severe myelosuppression resulting in a requirement for transfusions and which may lead to neutropenic infection; the risk of myelosuppression is increased in patients who do not receive vitamin supplementation
    • Initiate supplementation with oral folic acid and intramuscular vitamin B12 before the first dose of treatment; continue vitamin supplementation during treatment and for 21 days after the last dose to reduce the severity of hematologic and gastrointestinal toxicity of treatment;
    • Obtain a complete blood count at beginning of each cycle; do not administer treatment until the ANC is at least 1500 cells/mm3 and platelet count is at least 100,000 cells/mm3
    • Permanently reduce dose in patients with an ANC of less than 500 cells/mm3 or platelet count lower than 50,000 cells/mm3 in previous cycles
  • Drug interactions overview
    • Exposure to the drug is increased in patients with mild to moderate renal impairment who take concomitant ibuprofen, increasing the risks of adverse reactions; in patients with creatinine clearances between 45 mL/min and 79 mL/min, avoid administration of ibuprofen for 2 days before, the day of, and 2 days following administration of the drug; if concomitant ibuprofen use cannot be avoided, monitor patients more frequently for adverse reactions, including myelosuppression, renal, and gastrointestinal toxicity

Pregnancy and Lactation

  • Based on findings from animal studies and its mechanism of action, therapy can cause fetal harm when administered to a pregnant woman
  • There are no available data on pregnant women; in animal reproduction studies, IV administration of pemetrexed to pregnant mice during organogenesis was teratogenic, resulting in developmental delays and malformations at doses lower than the recommended human dose of 500 mg/m2; advise pregnant women of the potential risk to a fetus
  • Contraception
    • Females of reproductive potential: Use effective contraception during treatment for at least 6 months after the final dose
    • Males with female partners of reproductive potential: Use effective contraception during treatment and for 3 months after the final dose
  • Infertility
    • Therapy may impair fertility in males of reproductive potential; it is not known whether these effects on fertility are reversible
  • Contraception
    • Consider adequate contraception for women of childbearing potential
    • For women planning pregnancy, consider adequate contraception for 5 months after the last dose due to its elimination rate
  • Lactation
    • There is no information regarding the presence of the drug or its metabolites in human milk, its effects on the breastfed infant, or milk production; because of the potential for serious adverse reactions in breastfed infants, advise women not to breastfeed during treatment and for 1 week after the last dose.

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