PEMETREXED

Antifolate Antineoplastic Agent | Chemotherapy Medicine

Medical Description

Pemetrexed is a prescription antineoplastic medicine belonging to the class of folate analog metabolic inhibitors (antifolate agents). It interferes with folate-dependent cellular processes required for the synthesis of DNA and other cellular components, thereby inhibiting the growth and multiplication of rapidly dividing cancer cells.

Pemetrexed is administered intravenously by a healthcare professional and is generally given in treatment cycles. It is primarily used as part of chemotherapy regimens for selected forms of non-small cell lung cancer (NSCLC) and malignant pleural mesothelioma.

Main Clinical Uses

Pemetrexed is indicated for specific patients with:

• Locally advanced or metastatic non-squamous non-small cell lung cancer (NSCLC), commonly in combination with platinum-based chemotherapy.
• Metastatic non-squamous NSCLC, in combination with pembrolizumab and platinum chemotherapy in appropriate patients whose tumors do not have EGFR or ALK genomic aberrations.
• Maintenance treatment of non-squamous NSCLC when the disease has not progressed following initial platinum-based chemotherapy.
• Recurrent or metastatic non-squamous NSCLC after previous chemotherapy.
• Malignant pleural mesothelioma, generally in combination with cisplatin when the disease is unresectable or the patient is not a candidate for curative surgery.

Important: Pemetrexed is not indicated for squamous-cell NSCLC according to current U.S. prescribing information.

How Pemetrexed Works

Pemetrexed inhibits several folate-dependent enzymes involved in nucleotide synthesis. By interfering with the production of DNA and other molecules required for cell division, it can inhibit the proliferation of cancer cells. It is therefore classified as an antifolate antimetabolite chemotherapy agent.

Administration

Pemetrexed is supplied for intravenous administration and is given as an infusion over approximately 10 minutes by a qualified healthcare professional. For many approved indications, the standard regimen is administered on Day 1 of a 21-day treatment cycle, although the complete regimen depends on the cancer type and combination therapy being used.

For appropriate patients with adequate renal function, the commonly recommended dose is 500 mg/m² IV on Day 1 of each 21-day cycle. Dose adjustments or discontinuation may be required according to laboratory results, adverse reactions, and renal function.

Vitamin Supplementation

Because pemetrexed interferes with folate-dependent metabolic pathways, folic acid and vitamin B12 supplementation are an important part of treatment to reduce treatment-related toxicity.

Typical prescribing guidance includes:

• Folic acid: 400–1,000 micrograms orally once daily, beginning 7 days before the first pemetrexed dose and continuing until 21 days after the final dose.
• Vitamin B12: 1 mg intramuscularly approximately 1 week before the first dose and subsequently every 3 cycles.
• Dexamethasone: commonly administered around the time of pemetrexed treatment to reduce the risk of skin reactions.

These supplements are part of the medical treatment protocol and should not be omitted or substituted without medical advice.

Common Adverse Effects

Pemetrexed can cause adverse effects, including:

• Fatigue and weakness
• Nausea and vomiting
• Loss of appetite
• Diarrhea or constipation
• Skin rash or itching
• Hair loss
• Changes in taste
• Mouth sores
• Joint or muscle discomfort
• Decreased blood-cell counts, which may increase the risk of infection, anemia, or bleeding

Important Warnings & Precautions

Pemetrexed can cause serious and potentially life-threatening toxicities, and treatment requires medical supervision and laboratory monitoring.

Particular attention should be given to:

• Bone-marrow suppression: decreased white blood cells, red blood cells, and platelets can occur.
• Kidney toxicity: renal function should be assessed before and during treatment; dosing is dependent on renal function.
• Severe skin reactions: blistering, peeling, mucosal ulcers, or severe rash require urgent medical evaluation.
• Infection: fever, chills, sore throat, or other signs of infection should be reported promptly.
• Pulmonary toxicity: new or worsening cough or shortness of breath requires medical assessment.
• Pregnancy: pemetrexed may harm an unborn baby and requires appropriate pregnancy precautions.
• Breastfeeding: breastfeeding is not recommended during treatment and for the period specified by the prescribing information after the final dose.
• Fertility: pemetrexed may affect male fertility.

Patients should inform their oncology team about all prescription medicines, OTC medicines, vitamins, supplements, and herbal products they are taking. Certain medicines, including some NSAIDs, may require special consideration in patients with impaired renal function.

Patient Disclaimer

Pemetrexed is a prescription anticancer chemotherapy medicine and must be administered only under the supervision of a qualified oncology healthcare professional. The information above is for educational purposes and does not replace the prescribing information or individualized medical advice. Treatment, dose, treatment interval, laboratory monitoring, and combination medicines must be determined by the treating oncologist. Do not use, discontinue, or modify pemetrexed treatment without medical supervision.

References

1. U.S. FDA / DailyMed – Pemetrexed Injection, official prescribing information.
2. National Cancer Institute (NCI) – Pemetrexed Disodium.
3. National Cancer Institute – Non-Small Cell Lung Cancer Treatment (PDQ).
4. National Cancer Institute – Malignant Mesothelioma Treatment (PDQ).
5. U.S. National Library of Medicine – MedlinePlus, Pemetrexed Injection.