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What is finasteride and what is it used for?

Cropped SingleCare logo By | April 12, 2020
Medically reviewed by Marissa Walsh, Pharm.D., BCPS-AQ ID

What do male pattern baldness and enlarged prostate have in common? Both are treated with finasteride—and that’s where their similarity ends. What is it? This guide explains the conditions it treats, potential side effects, and alternative treatments. 

What is finasteride?

Finasteride is a 5-alpha reductase inhibitor. It works by blocking the production of the 4-alpha reductase enzyme, which changes testosterone into dihydrotestosterone (DHT), stimulating prostate growth and causing hair loss. The effect of DHT is local, meaning that the presence of it in the scalp doesn’t indicate an enlarged prostate and vice versa. Even so, finasteride, under different names and at different doses, is effective in treating both conditions. Brand names for finasteride include Proscar (for enlarged prostate) and Propecia (for hair loss). This medication might also reduce the risk of low-grade prostate cancer. 

What is finasteride used for?

The Food and Drug Administration (FDA) approved finasteride for the treatment of benign prostatic hyperplasia (BPH) and androgenetic alopecia, a gradual thinning of hair. Ask a healthcare provider about other off-label uses.

Benign prostatic hyperplasia

The brand name Proscar can be used alone or in combination with Cardura (doxazosin) to treat BPH, an enlargement of the prostate gland. When the prostate gland grows, it presses against the urethra. Symptoms of BPH, according to the Urology Care Foundation, include:

  • Urinary retention–being unable to empty the bladder fully
  • Feeling an urgency to urinate
  • Having a weak flow of urine
  • Difficulty with urination
  • Needing to strain to urinate

“Studies have shown that men taking finasteride for 12 months were noted to have a 23% reduction in obstructive and 18% reduction in nonobstructive scores, increased urinary flow, and a 19% reduction in mean prostatic volume,” says Douglas P. Jeffrey, MD, a family physician in Oregon and medical advisor for eMediHealth.“ It is important to take finasteride for six to 12 months before the size of the prostate is sufficiently reduced to improve the symptoms associated with the BPH.  The symptoms are relieved as long as the medication is continued for years.  Once the medication is stopped the original symptoms of BPH will generally return. The medication is considered safe for long term use.”

This risk for this condition increases with age. Half of all men between the ages of 51, and 60% to 90% of those older than 80 experiencing symptoms caused by an enlarged prostate, according to the National Institute of Diabetes and Digestive and Kidney (NIDDK). Finasteride can control BPH, but it does not cure it.  For some people, it decreases the need for prostate surgery. 

Male pattern baldness

Propecia can treat androgenetic alopecia—male pattern baldness. This medicine is a lower-dose of finasteride than Proscar. It helps improve receding hairlines and hair loss on the top of the scalp. However, it does not help thinning hair at the temples, according to Medline Plus

Propecia slows hair loss and can contribute to new hair growth, according to Kaiser Permanente. Many people do not see improvement for three to six months after starting the medication, and it only works if you continue to take it. If you stop, your new hair growth will fall out within six to 12 months of quitting. 

“Finasteride is more effective than topical treatments for male pattern hair loss,” according to Dr. Jeffrey.“Some studies report men achieve significant hair regrowth after two years of use with even more significant improvement in younger men between the ages of 18 and 41.” 

Finasteride is sometimes used to treat other conditions off-label. Off-label means that the FDA has not approved the drug for the treatment of the condition; however, anecdotal evidence has shown it might help. Some of these conditions include:

Hirsutism

This condition causes excessive hair growth in women. The hair growth appears on areas of the body where hair does not typically grow, such as on the upper lip, chin, chest, abdomen, and back. Between 5% and 10% of women have hirsutism, according to the Cleveland Clinic. Common causes include polycystic ovary syndrome (PCOS), menopause, some medications, and other health conditions caused by high testosterone levels. 

Transgender hormone therapy (male to female) 

Finasteride is sometimes useful in hormone therapy for transgender women to reduce the growth of hair on areas of the body other than the head. 

Prevention of prostate cancer

Finasteride might reduce the risk of low-grade prostate cancer. A large study found that finasteride substantially reduced the risk of prostate cancer in men aged 55 and older, according to the National Cancer Institute. This same study shows that although the drug lowers the risk of low-grade prostate cancer, it increases the risk for diagnosing high-grade prostate cancer, which is more aggressive and harder to treat. However, a more recent study, which followed men taking finasteride for 20 years, did not find an increase in prostate cancer-associated mortality.

Dr. Howard Parnes, one of the authors of the study, believes the initial results showing an increase in high-grade cancer are easily explainable, at least partially, by improved detection due to drug factors. Decreasing the size of the prostate gland increased the likelihood of obtaining a positive specimen upon biopsy for diagnosis, and finasteride seems to improve the sensitivity of the PSA test for the detection of high-grade prostate cancer. 

The FDA has not approved finasteride for cancer prevention.

Finasteride dosages

Finasteride is available in 1 mg and 5 mg tablets, according to the Physician’s Desk Reference (PDR). Typical dosages for the different conditions are:

  • BPH: 5 mg daily, taken with or without food, for a minimum of six months, up to 12 months if necessary. Use it alone or in combination with Cardura (doxazosin).
  • Male pattern hair loss: 1 mg daily for a minimum of three months. You should notice an improvement within 12 months. If there isn’t an improvement, further treatment is probably not going to be effective. You must have continued use to sustain the benefits of the medicine. 
  • Hirsutism in women: 5 mg daily, either alone or in combination with oral contraceptives. 
  • Transgender hormone therapy: 1 to 5 mg daily, according to Katie Imborek, MD, a co-director of the University of Iowa’s LGBTQ Clinic. 

What are the side effects of finasteride?

As with all drugs, finasteride can cause side effects. Not everyone experiences adverse reactions; however, you should be aware of the potential finasteride side effects, which can include sexual dysfunction. According to the PDR, common side effects include: 

  • Erectile dysfunction
  • Decreased sexual desire
  • Problems with ejaculation, including reduced volume of ejaculate
  • Pain in the testicles
  • Depression

More severe side effects, including an allergic reaction, are:

  • Rash
  • Itching
  • Hives
  • Swelling of lips and face
  • Difficulty breathing or swallowing

If you experience any of the severe side effects, you should contact your doctor or seek medical advice immediately. 

Finasteride might also increase your risk of developing breast cancer, according to the University of Michigan. You should contact a medical professional if you notice:

  • Breast lumps
  • Breast pain or tenderness
  • Nipple discharge
  • Other breast changes

Despite the possible side effects, “finasteride is relatively safe in use for improving hair growth for a portion of younger men. It should not be used without discussion. Careful review of potential short-term and long-term side effects and the understanding that loss of improvement nine to 12 months after stopping the finasteride are important to review prior to starting,” says Dr. Jeffrey. “Since finasteride has a tendency to decrease PSA levels it requires PSA to be monitored and to have a periodic digital rectal exam (DRE) to check the prostate. There is a possibility of masking prostate cancer due to the lowering of the PSA.  DRE should be performed prior to the start of therapy and at six months after start. Yearly DRE thereafter becomes important.”

Finasteride warnings

Some men experience post-finasteride syndrome (PFS) when they stop taking the medication. PFS includes persistent sexual, neurological, physical, and mental adverse effects. “Post-finasteride syndrome is not well defined and represents a controversial syndrome. It is associated with a group of sexual, physical, and psychological symptoms that develop during or after finasteride is started and may continue after discontinuation. Symptoms include decreased libido, ED, and ejaculatory dysfunction and depression,” according to Dr. Jeffrey. “In some cases, the symptoms disappeared over time though in others they lasted for many years.

There is no cure and few, if any, treatments, according to the PFS Foundation. The foundation indicates there have been 16,198 adverse drug reaction reports worldwide, 63 known suicides, and 23 nations that provide warnings about the medication. They are actively working to remove the drug from the market, or, at the very least, to have stronger warnings printed on all prescriptions and patient information sheets. 

Although finasteride has been linked to a decrease in low-grade prostate cancer, the 2003 study found it can increase your risk of developing high-grade prostate cancer, which is a more aggressive prostate cancer. Subsequent studies, such as the one published in Cancer Prevention Research, ultimately found no statistically significant increase in high-grade prostate cancer in those taking finasteride. 

Women who are pregnant or could become pregnant should not touch finasteride tablets as this medication may cause birth defects. 

Are there alternatives to finasteride?

Alternatives to finasteride depend on the reason you take medicine.

Avodart (dutasteride) for BPH

Avodart is a synthetic 4-azasteroid compound that treats BPH. It works by blocking the conversion of testosterone to dihydrotestosterone (DHT), which improves urine flow and might reduce the need for prostate surgery. Use it alone or with the medication Flomax (tamsulosin). 

Alpha-blockers for BPH

Alpha-blockers work by relaxing muscles in the bladder and prostate and help about 70% of men with BPH, according to Harvard Health. These begin working in approximately one to two weeks and have fewer side effects. Alpha-blockers include:

  • Rapaflo (silodosin)
  • Flomax (tamsulosin)
  • Uroxatral (alfuzosin)

They do not have any effect on the chance of developing prostate cancer.

Alternatives for male pattern baldness

In addition to finasteride, an over-the-counter topical treatment can combat male pattern baldness. Rogaine (minoxidil) is available as a liquid or foam, rubbed into the scalp daily, according to the Mayo Clinic. It can take at least six months before you start to notice further hair loss and new hair growth. The treatment only works while you are using it. When you stop, any new hair growth could be lost. 

Non-medication treatments include hair transplant surgery, or restoration surgery, and laser therapy. You might require more than one operation, and insurance typically does not cover these treatments.