What is flutamide used for? An overview of its indications and use

October 7, 2025 •

4 min read

First approved by the FDA in 1989, flutamide was the first nonsteroidal antiandrogen on the market, offering a new approach to hormone therapy. As a potent inhibitor of male hormones, understanding what is flutamide used for involves exploring its primary role in cancer treatment, as well as its historical application for androgen-dependent conditions in women.

Quick Summary

Flutamide is an antiandrogen medication used primarily in combination therapy for metastatic prostate cancer by blocking testosterone effects on cancer cells. It was also historically used to treat hyperandrogenism in women, though this is now rare due to severe liver toxicity risks.

Key Points

Prostate Cancer Treatment: Flutamide is a first-generation nonsteroidal antiandrogen used in combination with LHRH agonists to treat metastatic prostate cancer.
Mechanism of Action: It works by blocking androgen receptors on cancer cells, preventing androgens like testosterone from stimulating their growth.
Preventing Tumor Flare: When used with an LHRH agonist, flutamide helps prevent the initial testosterone surge and associated symptom flare that can occur.
High Risk of Liver Toxicity: Flutamide carries a significant risk of severe, potentially fatal liver damage (hepatotoxicity), requiring close and regular monitoring of liver function.
Superseded by Newer Drugs: Due to the severe hepatotoxicity risk and less convenient dosing schedule, flutamide has largely been replaced by newer, safer, and once-daily antiandrogens like bicalutamide and enzalutamide.
Historical Use in Women: Historically, flutamide was used off-label for conditions like hirsutism and PCOS in women, but this practice is now rare due to the high risk of liver damage.
Common Side Effects: Men taking flutamide commonly experience side effects such as hot flashes, diarrhea, gynecomastia, and decreased libido.

Primary Uses: Prostate Cancer

Flutamide is a first-generation nonsteroidal antiandrogen (NSAA) indicated primarily for the treatment of prostate cancer. Prostate cancer cell growth is often stimulated by androgens, or male hormones, particularly testosterone. Flutamide's main purpose is to interfere with this process, thereby slowing the growth and spread of cancer cells.

How Flutamide Works for Prostate Cancer

Flutamide works by blocking the effects of androgens at the cellular level. It acts as a competitive antagonist for androgen receptors, meaning it binds to these receptors but does not activate them. By occupying the androgen receptors on prostate cancer cells, flutamide prevents naturally occurring androgens like testosterone and dihydrotestosterone (DHT) from binding to them. Without the androgen 'fuel,' the cancer cells are inhibited from growing and spreading.

Combination Therapy with LHRH Agonists

Flutamide is not typically used as a standalone treatment for prostate cancer. Instead, it is most often prescribed in combination with a luteinizing hormone-releasing hormone (LHRH) agonist, such as leuprolide or goserelin. LHRH agonists work by suppressing the production of testosterone in the testes, which can lead to a temporary surge in testosterone levels, known as a 'tumor flare,' during the first few weeks of treatment. By administering flutamide a few days before the LHRH agonist, physicians can block this initial flare and mitigate its associated symptoms, such as increased bone pain or urination difficulties. For locally advanced or metastatic prostate cancer, this combination therapy forms part of a strategy known as combined androgen blockade.

Historical and Off-Label Uses in Women

Beyond its FDA-approved use in men with prostate cancer, flutamide has been used off-label to treat various androgen-dependent conditions in women. However, due to its significant risk of liver damage, its use for these purposes has become rare.

Hirsutism

Hirsutism, or excessive hair growth in a male-like pattern, is a condition often caused by high androgen levels, such as in polycystic ovary syndrome (PCOS). Flutamide's antiandrogen properties were effective in reducing unwanted hair growth by blocking the effect of androgens on hair follicles. While studies showed its effectiveness, the severity of potential side effects, including liver toxicity, has led clinicians to favor safer alternatives.

Polycystic Ovary Syndrome (PCOS)

Flutamide was used in women with PCOS to manage symptoms related to hyperandrogenism, such as hirsutism, acne, and seborrhea. It has demonstrated effectiveness in improving these symptoms, but again, the risk-benefit profile shifted with the availability of safer treatments.

Important Considerations: Side Effects and Risks

Flutamide therapy requires careful monitoring due to its potential for serious side effects, particularly liver damage.

Significant Liver Toxicity (Hepatotoxicity)

One of the most serious risks associated with flutamide is the potential for acute liver injury, which can be severe and, in rare cases, fatal. Symptoms of liver damage can include:

Jaundice (yellowing of the skin or eyes)
Dark urine
Light-colored stools
Nausea and vomiting
Right upper abdominal pain

Patients on flutamide must undergo regular blood tests to monitor liver function, especially during the first few months of treatment. Due to this risk, its off-label use for benign conditions is now strongly discouraged.

Common Side Effects

Patients, particularly men, may also experience several common side effects related to androgen deprivation, including:

Diarrhea
Hot flashes
Gynecomastia (enlarged or tender breasts)
Decreased sex drive and impotence
Nausea
Drowsiness

Flutamide in Modern Context: Why Alternatives are Preferred

Flutamide's use has declined significantly over the years due to the development of newer, safer, and more convenient antiandrogens.

Flutamide vs. Newer Antiandrogens


Feature	Flutamide	Bicalutamide (e.g., Casodex)	Enzalutamide (e.g., Xtandi)
Hepatotoxicity Risk	Significant and potentially fatal risk, requiring regular monitoring.	Much lower risk; considered to have a more favorable safety profile.	Lower risk compared to flutamide.
Dosing Frequency	Typically requires multiple daily doses due to a relatively short half-life.	Once daily (e.g., 50 mg) due to a longer half-life.	Once daily.
Side Effect Profile	Higher incidence of diarrhea, gynecomastia, and sexual side effects.	Lower incidence of diarrhea; similar sexual side effects.	Similar sexual side effects.
Convenience	Less convenient due to multiple daily doses.	More convenient with once-daily dosing.	Once-daily dosing offers high convenience.
Efficacy	Effective, but newer drugs offer equivalent or superior efficacy with better tolerability.	Considered equivalent to or better than flutamide in combination therapy.	Newer, more potent antiandrogen.

Flutamide Administration

For prostate cancer, flutamide is typically taken orally in capsule form. It is often initiated several days before starting an LHRH agonist to prevent the tumor flare phenomenon. The capsules are taken at regular intervals throughout the day. Regular blood tests are mandatory to monitor for liver function, as specified by the prescribing physician.

The Future of Flutamide

Due to the significant risk of serious hepatotoxicity, flutamide is no longer considered a first-line treatment for prostate cancer and is rarely used for benign conditions like hirsutism. Its primary use today is as an alternative for patients with a limited number of treatment options or those who cannot tolerate newer medications. However, even in these cases, the risk-benefit profile must be carefully evaluated by a healthcare team. The landscape of antiandrogen therapy has shifted significantly towards safer, more effective, and more convenient options, which has cemented flutamide's status as a less common therapeutic agent in modern medicine.

For more detailed medical information on flutamide, including its toxicology, a review by the National Institutes of Health's LiverTox project offers comprehensive insights.

Note: This information is for educational purposes only and should not be considered medical advice. Patients should always consult with their healthcare provider regarding specific treatments and medical conditions.

Frequently Asked Questions

Flutamide is a nonsteroidal antiandrogen (NSAA) medication that blocks the effects of male hormones, such as testosterone, from promoting cell growth in the body.

Flutamide's use has declined because newer antiandrogens like bicalutamide and enzalutamide are safer, more convenient (once-daily dosing), and have a much lower risk of serious liver toxicity.

For prostate cancer, flutamide is not typically used alone and is instead combined with another hormone therapy, such as an LHRH agonist.

The most serious side effect is liver damage, or hepatotoxicity, which can be severe and life-threatening in rare cases. Patients are monitored with regular blood tests to check liver function.

Common side effects in men include hot flashes, diarrhea, nausea, gynecomastia (breast enlargement), breast tenderness, and a decrease in sexual desire and ability.

While it was historically used off-label for conditions like hirsutism and PCOS, this practice is now discouraged due to the risk of severe liver toxicity. Safer alternatives are available for these conditions.

According to prescribing guidelines, liver function tests should be conducted before starting treatment, monthly for the first four months, and periodically thereafter.