Adverse Effects of 5 Fluorouracil (5-F.U.)

Brand Names include: Adrucil, Carac, Efudex, and Flurodex

One of the most popular medicinal creams prescribed today, 5 Fluorouracil (5-F.U.) cream is a topical chemo-therapeutic agent that was patented in 1956. The 5-F.U. acts by blocking the production of pyrimidine thymidine, an organic compound that is essential for DNA replication. In other words, 5-F.U. kills cancer cells by mutating these rapidly dividing cells in such a way that they cannot replicate properly.

While this result is desirable, the resulting mutation also affects other rapidly dividing normal cells, such as the epidermal cells of the skin. In fact, chronic exposure to mutation dramatically increases the chance that normal skin cells will convert into cancer cells. Therefore, while 5-F.U. cream is very effective in killing cancer and precancer cells, it can have a significant negative effect by promoting potential cancer in the surrounding healthy epidermal cells.

The skin’s reaction to the application of 5-F.U. cream is commonly severe inflammation with redness, swelling, and even weeping wounds. It is typically used for about three weeks, temporarily leaving the skin clear and beautiful. However, each time 5-F.U. cream is used, additional epidermal cell mutations are created, potentially leading to more pre-cancers and cancers.

Thus, if 5-F.U. cream is continually used to treat new cancers and precancers, it will need to be used with increased frequency and for a longer duration. This “rebound phenomenon” starts one to five years after the start of 5-F.U. usage.

As a Beverly Hills dermatologist, I never prescribe any type of 5-F.U. cream unless other preferable treatments are impractical – primarily when the patients are is very elderly and incapacitated. In their case, the patients’ short-term benefit of killing cancer cells outweighs the long-term harm from the possibility of creating new cancer cells.

As an alternative, I have had great success using Aldara or Zyclara (Imiquimod).  My preferred treatment is liquid nitrogen followed by a Natural Marine Extract topical, the ingredients of which safely stimulate the immune system to kill cancer cells.

Please note that like 5-FU, Aldara and Zyclara also cause inflammation and scabbing of the skin.

For Further Reading on the Potential Side-Effects of 5-FU:

Abramson Cancer Center of the University of Pennsylvania’s Oncolink®