Episode 288: Pharmacology 101: Antimetabolites

“I think that there are certain agents that are so foundational in some diseases that they will remain. Whether they remain first-line, maybe not; maybe they’ll go to second line as we see things evolve with new agents. Some of these drugs have been very effective in the diseases in which they are used to treat patients. There’s a long term place in therapy for these, and I think that will still be using these,” Rowena Schwartz, PharmD, BCOP, FHOPA, known to many as “Moe,” professor of pharmacy practice at James L. Winkle College of Pharmacy at the University of Cincinnati in Ohio, told Lenise Taylor, MN, RN, AOCNS®, BMTCN®, oncology clinical specialist at ONS, during a discussion about what oncology nurses need to know about antimetabolites. This episode is part of a series about drug classes, which we’ll include a link to in the episode notes. 

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Music Credit: “Fireflies and Stardust” by Kevin MacLeod 

Licensed under Creative Commons by Attribution 3.0 

Earn 0.5 contact hours of nursing continuing professional development (NCPD), which may be applied to the oncology nursing practice and treatment ILNA categories, by listening to the full recording and completing an evaluation at myoutcomes.ons.org by December 1, 2025. The planners and faculty for this episode have no relevant financial relationships with ineligible companies to disclose. ONS is accredited as a provider of NCPD by the American Nurses Credentialing Center’s Commission on Accreditation. 

Learning outcome: The learner will report an increase in knowledge related to antimetabolites. 

Episode Notes 

To discuss the information in this episode with other oncology nurses, visit the ONS Communities.  

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Highlights From Today’s Episode 

“Antimetabolites are relatively old agents. They are some of the oldest anti-cancer drugs that we have. They were developed to be similar to naturally occurring compounds that are important in cellular production. They are similar but not the same. So, they sometimes will bind to an enzyme important for cell proliferation. And because it binds to an enzyme, does it mean that it helps the enzyme? It may block it and that may cause cell death. And so, they’ve been used for a long time in oncology.” TS 1:44 

“There's different classes of antimetabolites in oncology. If you think of the structure of DNA, there is purines, that’s adenine and guanine, there are pyrimidines, which are things like cytosine and limonene, and then in RNA there's uracil. So, some of the antimetabolites are either purine analogues or pyrimidine analogues, meaning they look very much like the natural parts of DNA, and by being incorporated into the DNA they cause cell death. There's also a class of antimetabolites that interfere with how we use folate in the body, such as methotrexate is an obvious one, and these are called folate antagonists.” TS 2:43 

“The purine analogs—and those are things like fludarabine or clofarabine—those drugs are very toxic to lymphocytes. And because they’re very toxic to lymphocytes, these are drugs that we use in lymphocytic diseases. But that also means that these are drugs that we get immunosuppression because of the toxicity to lymphocytes. So, these patients have risk of infections because of their decreased lymphocyte activity after receiving these drugs.” TS 6:37 

“Methotrexate works by blocking an enzyme that decreases the ability to make the folate that we need in our body to make cells. So, one of the things that we do when we use really high doses of methotrexate is we let it work for 24 hours and then we come in and we give leucovorin, which is the thing that we blocked. So, you're coming into rescue cells. And you're rescuing cells because the cancers we use high-dose methotrexate, we know that 24-hour exposure is going to be a really good effect on those cancer cells. So that's why we use leucovorin after methotrexate. We use it to minimize the toxicities that you would see with methotrexate. You decrease GI mucositis; you decrease the bone marrow suppression when you come in and adequately rescue with leucovorin.” TS 12:22  

“I think [that’s] one of the biggest challenges. I just had a situation that was an antimetabolites drug I’d never used before. I couldn't find in the literature and through resources I normally use, how to manage, so I actually reached out to colleagues to find out, who have used the medications to say, ‘What's your experience? What's worked for you?’ It's one of the reasons I really love ONS, because I think it gives a forum for people to ask those questions together.” TS 15:23 

“I think developing good patient education tools that people can take home that highlight the most important things about the regimen, including the antimetabolite aspects, making sure patients know what to monitor for so that they can contact their team if they need them. Diarrhea is something I always talk about with patients getting 5-fluorouracil. I do it because otherwise people self-manage and don’t actually know what to do, and we really want to make sure that they contact us if they’re having problems with diarrhea.” TS 17:14 

“I think one of the best things that people can do is work together in the development of the order sets, whether they be electronic or not. And, so, that within the order sets there is clear indications of those things that highlight to patients the strategies to take, to manage. I think that's really helpful, and I think it's best done by a team. And to modify those order sets as things are learned that are helpful so that, you know, the strategy is dose reduction that's clear that that's going to be the strategy. So, I think that in this day and age it's really important that there is collaboration in developing whatever resources that we have.” TS 18:55 

“Because gemcitabine is such a good radio sensitizer, when we use it with radiation, we use a very small dose. Very small. We're not talking anything near what we use when we use it in combination chemotherapy. So, when you have a patient getting gemcitabine, if somebody decides that they're going to do radiation, you have to make sure everybody knows they're on gemcitabine because you may hold the drug while they're getting radiation because you don't want to increase in toxicity.” TS 22:31 

“I think that there are so many new, exciting agents and there are so many older agents that are still used in practice, that it's becoming very difficult for people to understand the mechanisms of the drugs that we're using and the agent-specific toxicities. So, I think that the education that's needed is the foundation and fundamentals of chemotherapy, because they still are used so much in practice. And I would hate to lose the knowledge that practitioners have because we're excited about the new, exciting therapies that are new and exciting.” TS 25:09 

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