5-Fluorouracil Injection

Generic name: fluorouracil (injection) [ FLOOR-oh-URE-a-sil ]
Brand names: Adrucil injection, Adrucil
Dosage form: intravenous solution (50 mg/mL)
Drug class: Antimetabolites


In cancer treatment, 5-fluorouracil injection is the prime medication, wielding its efficacy against various malignancies. Abbreviated as 5-FU, this chemotherapy drug is a potent tool in oncologists' arsenal, precisely targeting cancer cells. Lets explore the different aspects of 5-fluorouracil injection and more.

What is 5-Fluorouracil Injection?

At the core of its mechanism lies the ability to disrupt the proliferation of cancer cells by interfering with their DNA synthesis. As an antimetabolite, 5-Fluorouracil mimics the structure of natural substances within the body, fooling cancer cells into incorporating it during DNA replication. Once integrated, it hampers the process, leading to cell death and impeding tumor growth.

Uses of 5-Fluorouracil Injection

Colorectal Cancer

The foremost application of 5-Fluorouracil injection lies in combating colorectal cancer, where it often features prominently in chemotherapy regimens, either as a standalone treatment or in combination with other drugs like oxaliplatin or irinotecan.

Breast Cancer

In cases of advanced breast cancer, mainly when metastasis has occurred, 5-FU may be employed to impede tumor progression and alleviate symptoms.

Gastric Cancer

Treatment protocols for gastric cancer frequently include 5-Fluorouracil injection, either as neoadjuvant therapy to shrink tumors before surgery or as adjuvant therapy post-surgery to eradicate residual cancer cells.

Pancreatic Cancer

While challenging to treat, pancreatic cancer may benefit from the addition of 5-FU to chemotherapy regimens, often in combination with other agents like gemcitabine.

Skin Cancer

Certain types of skin cancers, such as basal and squamous cell carcinoma, respond favorably to 5-Fluorouracil injection, offering a non-surgical option for treatment, particularly in cases where surgery is not feasible.

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Side Effects of 5-Fluorouracil Injection

  1. Nausea and Vomiting: Nausea and vomiting are among the most common side effects, and they can significantly impact a patient's quality of life during treatment.
  2. Diarrhea: Gastrointestinal disturbances, including diarrhea, are frequent occurrences with 5-FU therapy, often necessitating supportive care and management.
  3. Loss of Appetite: Decreased appetite and weight loss are prevalent side effects, which may contribute to nutritional deficiencies and weakness.
  4. Mouth Sores: Oral mucositis, a painful mouth sores, can develop, making eating and speaking uncomfortable for patients.
  5. Fatigue: Profound fatigue is a hallmark side effect of chemotherapy, including 5-fluorouracil injection. It impacts daily functioning and requires adequate rest and support.
  6. Hair Loss: While not as common as other chemotherapy agents, hair loss (alopecia) may occur with 5-FU treatment, albeit usually temporary.
  7. Hand-Foot Syndrome: This unique side effect is redness, swelling, and pain on the palms of hands and soles of feet. It can affect mobility and agility.
  8. Low Blood Cell Counts: Bone marrow suppression can lead to decreased red blood cells (anemia), white blood cells (leukopenia), and platelets (thrombocytopenia).
  9. Skin Reactions: Various skin reactions, including rash, dryness, and itching, may occur, necessitating gentle skin care and avoidance of irritants.
  10. Increased Sensitivity to Sunlight: Photosensitivity reactions, such as sunburn and skin damage, are heightened during treatment with 5-Fluorouracil injection, emphasizing the importance of sun protection.

Administration Of Fluorouracil?

The administration of 5-fluorouracil injection typically occurs intravenously and is delivered directly into a vein by a trained healthcare professional. Depending on the prescribed dosage and infusion rate, the infusion process may take several hours. Some patients may receive continuous infusion pumps to ensure a steady medication delivery over an extended period.

Fluorouracil Dosing Details

Usual Dose - Colorectal Cancer

For colorectal cancer treatment, the typical dosage involves administering 400 mg/m2 intravenously as a bolus on the first day, followed by 2400 to 3000 mg/m2 as a continuous intravenous infusion over 46 hours, every two weeks.

Bolus Dosing Regimen with Leucovorin

Combined with leucovorin, a bolus dosing regimen involves administering 500 mg/m2 intravenously on Days 1, 8, 15, 22, 29, and 36, within 8-week cycles. This flexible dosing schedule, utilizing bolus injections of fluorouracil and leucovorin, may be preferred in specific clinical situations.

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What To Do Prior Of Administration?

Before initiating treatment with 5-Fluorouracil injection, you should have a thorough assessment and consultation. Patients should disclose their complete medical history, including any pre-existing conditions, allergies, or medications they are currently taking. Special consideration should be given to women who are pregnant or breastfeeding, as well as individuals with liver or kidney impairment, to mitigate potential risks and optimize treatment outcomes.

Warnings of 5-Fluorouracil Injection

Bone Marrow Suppression

One of the most significant concerns with fluorouracil treatment is the potential for bone marrow suppression, leading to decreased blood cell counts and increased susceptibility to infections and bleeding.


In some instances, fluorouracil may cause cardiotoxic effects, including chest pain, arrhythmias, and myocardial ischemia, necessitating close monitoring of cardiac function during treatment.

Gastrointestinal Toxicity

Severe gastrointestinal adverse events, such as diarrhea, dehydration, and mucositis, can occur, requiring prompt intervention and supportive care measures.


Although rare, neurotoxic effects, including confusion, dizziness, and peripheral neuropathy, may manifest, warranting careful observation and management.


Fluorouracil therapy may cause hepatic dysfunction, known by elevated liver enzymes and hepatomegaly, necessitating regular monitoring of liver function tests.

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Interactions with 5-Fluorouracil Injection

  1. Warfarin: Concurrent use of warfarin with fluorouracil may potentiate the risk of bleeding, necessitating close monitoring of prothrombin time and INR levels.
  2. Phenytoin: Phenytoin may diminish the effectiveness of fluorouracil by accelerating its metabolism, potentially reducing therapeutic efficacy.
  3. Leucovorin: Co-administration of leucovorin with fluorouracil can enhance the efficacy of fluorouracil-based chemotherapy regimens, particularly in colorectal cancer.
  4. Allopurinol: Allopurinol may exacerbate the toxicity of fluorouracil by interfering with its metabolism, increasing the risk of adverse reactions.
  5. Live Vaccines: They should be avoided during treatment to prevent vaccine-induced infections and suboptimal immune responses.

Precautions for 5-Fluorouracil Injection

Pregnancy and Breastfeeding

The use of fluorouracil during pregnancy or breastfeeding should be approached with caution, considering the potential risks to fetal development and infant health.

Hepatic Impairment

Patients with pre-existing liver disease or impaired hepatic function may be at increased risk of hepatotoxicity with fluorouracil treatment, necessitating dose adjustments and close monitoring.

Renal Impairment

Renal function should be assessed before initiating fluorouracil therapy, with dose modifications made in patients with impaired kidney function to prevent drug accumulation and toxicity.

Elderly Patients

Elderly patients may be more susceptible to specific side effects of fluorouracil, such as bone marrow suppression and cardiotoxicity, requiring vigilant monitoring and supportive care.

Sun Exposure

Patients receiving fluorouracil treatment should exercise caution when exposed to sunlight, as photosensitivity reactions may occur, leading to sunburn and skin damage. Adequate sun protection measures, including sunscreen and protective clothing, are essential to minimize the risk of skin reactions.

In Case a Dose is Missed

If a dose of 5-Fluorouracil injection is missed, patients should promptly notify their healthcare provider for further guidance. Attempting to administer extra doses to compensate for the missed dose is not recommended and may increase the risk of adverse effects or toxicity.

Also Read: 10 Tips To Live Your Life After a Lung Cancer Diagnosis


5-Fluorouracil injection is a strong support in the battle against cancer, offering hope and respite to patients confronted with the formidable challenges of this disease. 5-FU necessitates careful consideration of its potential side effects. Lets navigate the complexities of cancer treatment with diligence, compassion, and unwavering determination.


Can fluorouracil cure cancer?

While not typically curative on its own, fluorouracil plays a pivotal role in cancer treatment, often contributing to disease control and symptom management as part of therapeutic strategies.

How long does it take for fluorouracil to work?

The timeline for observing the therapeutic effects of fluorouracil varies depending on factors such as cancer type, stage, and individual response to treatment. Patients may begin to notice improvements within weeks to months of initiating therapy.

What should I do if I experience severe side effects with fluorouracil?

In the event of severe or debilitating side effects, patients should seek immediate medical attention and notify their healthcare provider for prompt evaluation and management of symptoms.

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