What Is Flutamide (Eulexin®)?

Eulexin® (flutamide) is an androgen receptor inhibitor, also called an antiandrogen or a nonsteroidal antiandrogen (NSAA), that is used in combination with other hormone therapies called LHRH agonists (also called GnRH agonists). It may be used in individuals with prostate cancer that is locally confined or that has metastasized (spread to other parts of the body). Flutamide is an orally administered medication that comes in capsule form. Individuals taking flutamide should also be monitored for changes in liver functioning as well as any other liver conditions.

How does flutamide work?

Flutamide’s active ingredient binds to androgen receptors in the body. Flutamide blocks testosterone and other androgens from activating these receptors. Prostate cancer tumors are often fueled to grow by androgens, including testosterone. Turning off the body’s ability to respond to testosterone can potentially halt tumor growth. In addition, flutamide can be used during early stages of other hormone therapies, such as treatment with Gonadotropin-Releasing Hormone (GnRH) agonists, in order to block the initial surge of testosterone, called tumor flare, that can come along with these medications. The surge of testosterone at the beginning of some of these treatment methods can contribute to rapid tumor growth before it is halted, potentially leading to life-threatening issues such as spinal cord compression.

What are the possible side effects of flutamide?

Multiple clinical trials evaluated the safety and efficacy of flutamide. Possible side effects of flutamide include hot flashes, swelling or pain of the breasts, decreased libido, impotence, diarrhea, nausea, and vomiting. These are not all the possible side effects of flutamide. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with flutamide.

Things to note about flutamide

Less common but more serious side effects can accompany flutamide including problems with your liver. Individuals should be closely monitored for signs of these serious side effects, and blood tests to assess liver function should be performed regularly. Patients should take their medication as prescribed by their doctor. Patients should talk to their doctor if they have any questions, or if they have questions regarding their flutamide regimen. Alert your provider immediately if you notice any of the following symptoms:

  • Nausea and vomiting
  • Stomach or abdominal pain
  • Flu-like symptoms like soreness or muscle aches
  • Fatigue
  • Brown urine
  • Yellowing of the skin or whites of eyes (jaundice)
  • Loss of appetite
  • Inability to urinate

You should also contact your provider if you notice any signs of an allergic reaction to the medication, including chest pain or difficulty breathing. It is also important to consult the prescribing information for any other medications taken with flutamide, including any LHRH agonists.

Before starting flutamide talk to your provider if you:

  • Have any liver problems
  • Have any other medical conditions
  • Are currently taking any other medications (prescription and over-the-counter), vitamins, or herbal supplements

Receiving flutamide

Flutamide is administered orally and is commonly taken with a LHRH (or GnRH) agonist. Your provider will determine the appropriate dosage and administration schedule for you, as well as the appropriate dosage and administration of any other medications taken with flutamide. It is important to follow this schedule exactly as instructed, and not to stop taking flutamide or any accompanying medications on your own.1

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Written by: Casey Hribar | Last reviewed: March 2022