Pemetrexed and Vitamin B12 interaction
Pemetrexed and Vitamin B12: the Pemetrexed prescribing label describes an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Pemetrexed (Pemfexy) label · effective 2026-02-20
Initiate supplementation with oral folic acid and intramuscular vitamin B 12 to reduce the severity of hematologic and gastrointestinal toxicity of PEMFEXY.
Initiate supplementation with oral folic acid and intramuscular vitamin B 12 prior to the first dose of PEMFEXY; continue vitamin supplementation during treatment and for 21 days after the last dose of PEMFEXY to reduce the severity of hematologic and gastrointestinal toxicity of pemetrexed [see Dosage and Administration ( 2.4 )] .
…versus 23%), thrombocytopenia (9% versus 5%), febrile neutropenia (9% versus 0.6%), and neutropenic infection (6% versus 0) were higher in patients who received pemetrexed plus cisplatin without vitamin supplementation as compared to patients who were fully supplemented with folic acid and vitamin B 12 prior to and throughout pemetrexed plus cisplatin treatment.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.