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What are 5-fluorouracil¡¯s side effects?

Hand-foot syndrome is probably the most common. As the name implies, it primarily affects the palms of the hands and the soles of the feet. It causes a discoloration of the skin. This discoloration sometimes appears as redness, which can almost look like a sunburn.  

Normally, patients don¡¯t notice any difference in the way the affected skin feels, even if it looks different. But if it starts bothering you, you can apply a thick moisturizing lotion two or three times a day. The lotion should be unscented, though, because perfumes dry out the skin even more. 

In the very rare instances when patients develop blisters or their skin becomes so dry it starts cracking or peeling, we may consider adjusting their chemotherapy dose.  

Other side effects associated with 5-FU include: 

Nausea

When taken on its own, 5-FU has a low risk of causing nausea. But because it is rarely given that way, patients often experience nausea due to the other drugs it¡¯s given in combination with. If nausea develops, we can treat it with antiemetic medications. 

Hair loss

5-FU is also not typically associated with significant hair loss, though it may cause some minor hair thinning that only you would notice. This means you might see more hair ending up on your brush or in your shower drain than usual. But it¡¯s not the type of hair loss that¡¯s going to make someone look at you and think, ¡°Oh, she¡¯s definitely getting chemotherapy,¡± if they see you out in public.  

Diarrhea

5-FU can cause mild to moderate diarrhea, but it¡¯s not one of the worst offenders. Just make sure you have over-the-counter anti-diarrheal medications on hand at home, so you can take them, if needed. 

Mouth sores

5-FU can sometimes cause mucositis, or sores in the mouth and throat. To prevent this, we recommend rinsing your mouth out with a baking soda solution four or five times a day: once after every meal, and once after waking and again before going to bed.  

We don¡¯t recommend this regimen to everyone because mucositis may never become an issue. It¡¯s more common if we¡¯re giving someone bolus doses of 5-FU versus a continuous infusion.  

But if you develop mouth sores and they interfere with your ability to eat, we have other prescription mouth rinses that can help. 

Photosensitivity

5-FU can make you more sensitive to sunlight, but that doesn¡¯t mean you can¡¯t go outside. It just means you have to be a little more cautious when you do. You¡¯re more likely to get sunburns on 5-FU therapy and if you do get them, they will likely be more severe.  

So, dress in layers, wear a big hat and sunglasses, and cover any exposed skin with SPF 30 sunscreen or higher while receiving treatment with 5-FU. 

Coronary vasospasm

This is a very rare side effect of 5-FU, but it¡¯s worth mentioning because it can be severe and feel scary. Coronary vasospasm describes a condition when the arteries that supply the heart with blood suddenly narrow, which restricts the heart¡¯s blood supply. This may cause chest pain, tightness and difficulty breathing. It can feel like you¡¯re having a heart attack. 

Coronary vasospasm usually happens during or after a patient¡¯s very first exposure to 5-FU. So, if you don¡¯t experience it then, you might not experience it at all. If you ever do, though, and you¡¯re not already at a hospital, go straight to an ER. There¡¯s a small possibility you might actually be having a heart attack, so you don¡¯t want to take any chances. 

If you develop coronary vasospasm as a side effect, we may stop giving you 5-FU entirely or change the way we administer it. We may also ask our cardiology team to help monitor you and provide prevention strategies to avoid future problems. 

Stacy Diao is a clinical pharmacist at MD Anderson.

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