Active Ingredients

5-Fluorouracil – Effect, Application & Risks


5-Fluorouracil is a cytostatic used in human medicine. It is used as part of a holistic chemotherapy under medical supervision in order to treat so-called malignant (“malignant”) tumors in various parts of the body. Due to the strong side effects , there is a strict pharmacy and prescription requirement within the European Union.

What is 5-Fluorouracil?

The medicinal substance 5-fluorouracil (abbreviated: 5-FU ) is often also called fluorouracil (abbreviated: INN ). Both designations stand for a heterocyclic organic compound that is built on a pyrimidine basis. The active substance inhibits the growth of cells and is therefore included in the drug group of cytostatics. 5-Fluorouracil is thus administered as part of a holistic chemotherapy to treat malignant tumours.

5-Fluorouracil is commonly used to treat breast cancer or colorectal cancer or tumors of the gastrointestinal tract . Furthermore, the use for the treatment of warts is conceivable in lower doses. In these cases, the active ingredient is processed into a cream intended for external use.

5-FU has been marketed internationally since the 1960s and was developed by the American chemist Charles Heidelberger. In chemistry and pharmacy, the substance is described by the empirical formula C 4 – H 3 – F – N 2 – O 2 , which corresponds to a moral mass of approx. 130.08 g/mol. At room temperature, 5-FU is a white powder. It is water-soluble and can be processed into an infusion solution.

Pharmacological effect on body & organs

5-Fluorouracil is a representative of the class of active substances known as antimetabolites. This includes chemical compounds that inhibit the process of metabolizing natural metabolites and therefore have an inhibiting effect on the physiological processes of the body.From a chemical point of view, 5-fluorouracil also resembles the pyrimidine analogues because of its structural similarity to the pyrimidine base uracil. Various medicinal substances derived from the organic compound pyrimidine can be subsumed under this term.

5-Fluorouracil inhibits thymidilate, an essential enzyme in pyrimidine biosynthesis. This prevents the conversion of dUMP (deoxyuridine monophosphate) into dTMP (deoxythymidine monophosphate), which in turn leads to inhibition of cell growth . In this way, 5-fluorouracil is particularly successful in preventing cells with a high rate of division from multiplying.

Medicinal Application & Use for Treatment & Prevention

5-Fluorouracil is indicated both alone and in combination with other preparations. The administration with the drug folinic acid has proven to increase the cytotoxic effect of 5-FU again (so-called FOLFIRI or FOLFOX scheme).

In general, 5-fluorouracil is considered a highly effective drug that has a broad spectrum of effectiveness. The potential area of ​​application is therefore particularly large. Administration of 5-fluorouracil is particularly indicated for various tumor diseases. In particular, malignant tumors of the gastrointestinal tract (gastrointestinal tract) such as colorectal carcinoma, anal carcinoma or esophageal carcinoma can be treated.

In addition, there is also an indication for the treatment of malignant tumors in the head and neck area ( squamous cell carcinoma ). 5-FU is also often used as part of chemotherapy to treat breast cancer (mammary carcinoma).

If 5-fluorouracil is used to treat carcinomas, it is administered intravenously as part of chemotherapy. The drug itself is issued exclusively to doctors and sold as a powder for making up an infusion solution. There is a strict prescription and pharmacy obligation within the European Union, so that independent purchase by the patient is excluded.

In addition to cancer therapy, 5-FU is also processed in a weakened concentration in creams intended for the topical treatment of warts.

Risks & side effects

Since 5-FU is a highly effective cytostatic, there are numerous risks and side effects . Immense interactions with other medicinal substances must also be taken into account. The use of 5-Fluorouracil must be completely avoided if there is a contraindication. This is always the case when there are circumstances that would lead to unmanageable risks and therefore make treatment with the active ingredient appear unreasonable from a medical point of view (contra-indication). Such circumstances exist, among other things, if intolerances or allergies are known.In addition, 5-fluorouracil is contraindicated if there are severe changes in the blood count , bone marrow dysfunction or blood formation disorders . Patients suffering from acute infections or severe liver dysfunction should also not take 5-FU. During pregnancy and lactation , 5-fluorouracil can lead to significant deformities, which is why any contact with the substance should be avoided.

The usual undesirable side effects that can occur during or shortly after taking 5-fluorouracil include primarily gastrointestinal complaints. These manifest themselves as severe nausea , diarrhea , vomiting or mucositis. In addition, disorders of the blood formation system are also conceivable. Bone marrow depression in particular can be attributed to the intake of 5-fluorouracil. In some cases, hand-foot syndrome may also develop after ingestion.

The extent of the respective side effects depends on the individual case. In particular, the dose administered is important for the intensity of the symptoms.

Interactions are conceivable , especially with various antivirals . The active substance brivudine (Zostex) can lead to serious interactions. The same is the case when taking 5-FU prodrugs such as capecitabine at the same time . A safety interval of at least four weeks between intakes should be maintained.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.