Finasteride is the only oral medication that’s FDA-approved to treat hair loss. This drug was originally used to treat a prostate condition called benign prostate hyperplasia (BPH). A few years later, it was approved for androgenetic alopecia, the most common form of hair loss. Technically, both men and women can use finasteride, but this prescription-only drug is only FDA-approved for men.
When used for BPH, finasteride is taken in daily doses of 5 milligrams. Finasteride for hair loss is taken orally in lower doses of 1 milligram per day. The risk and type of side effects from this drug may differ based on the dose you’re taking.
What Is Finasteride?
Finasteride is an oral 5-α reductase inhibitor that reduces dihydrotestosterone (DHT), the main hormone responsible for the progression of pattern hair loss.(1,2) A study of male Japanese finasteride users found that the drug improved hair growth in 87.1 percent of men up to 70 years of age. It works up to 50% of the time in men over 70.(3)
Finasteride is not an immediate fix. Like other hair loss treatments, it typically starts working about 3 months after taking the medication. People usually see noticeable improvements after a year of taking the medication, but the finasteride’s full effects may take 2-5 years to see.(4)
Most men can take finasteride safely for either BPH or pattern hair loss. But both the 5-milligram and 1-milligram doses come with a small risk of unpleasant and sometimes serious side effects.
Finasteride can also be useful for hair loss in women. However, this would be an off-label use as this medication is not yet FDA-approved for this purpose.
Finasteride Side Effects
Many people don’t experience side effects after taking finasteride. However, a small percentage of men may develop one or more unpleasant side effects. Symptoms include a wide range of physical and psychological issues, including loss of libido, erectile dysfunction, depression, insomnia, suicidal ideation, and the inability to feel pleasure (anhedonia).
Finasteride’s side effects don’t seem to be dose-dependent. The physical and psychological issues associated with this drug have been attributed more to the 1-milligram dose than the 5 milligram dose.(5,6)
Finasteride 1 mg Side Effects
When taken as the 1 milligram daily dose, finasteride is usually well-tolerated, even with extended use. A long-term study conducted in 2017 evaluated over 4,300 male finasteride users under the age of 42. It found that taking a 1 milligram dose was significantly associated with continued sexual dysfunction in about 0.8% of the men studied, even after they stopped taking the medication. (7)
Strangely, the physical side effects associated with finasteride, such as loss of libido and reduced ejaculation, as well as psychological symptoms, including depression and insomnia, have been associated more often with the daily 1-milligram dose than the 5-milligram dose (5,6). Similarly, there was speculation that the 5-milligram dose increased suicide risk, but it was determined that the adverse psychological effects were more common when taking the 1-milligram dose.(8)
Despite these findings, finasteride’s side effects may still be dose dependent. High and low-dose finasteride pills are prescribed to completely different people.
Most people taking the 5 milligram dose of finasteride are people with BPH. This prostate condition occurs much more often in older men, affecting 20 percent of men aged 40 compared to 90 percent of men in their 70s. This means that most people taking finasteride for BPH are older men who may have already experienced problems with sexual dysfunction. In contrast, typical finasteride users tend to be healthy men in their mid-40s or younger.(9,24)
Considering this age difference, a recent meta-analysis concluded that 1 milligram finasteride users may simply be more prone to finasteride’s psychological side effects. Younger men are more likely to be bothered by issues like sexual dysfunction – especially since they’re already likely anxious about their hair loss – and consequently be more prone to depression, anxiety, and other negative mental health effects.(9)
Finasteride 1 mg Side Effects in Women
Finasteride can be useful for hair loss in women and has been assessed in a number of studies. However, women face a number of other possible unpleasant side effects. Some of the most commonly reported side effects include symptoms like fatigue, arthritis, and menstrual changes.(6)
Pregnant women should never take this drug as it can cause complications during pregnancy and even has the potential to induce spontaneous abortion. In fact, the FDA-approved drug label for Propecia’s label even says pregnant women should not even handle broken or crushed medication.(10)
Finasteride 5 mg Side Effects
The 5-milligram dose of finasteride is mainly used to treat BPH. However, since both pills are made using the same active ingredient, the higher dose pills can also help men improve hair growth. Like with 1-milligram doses of finasteride, most people taking the higher dose of this drug experience little to no issues. However, 5-milligram finasteride users have reported side effects including breast tissue growth, rashes, sexual dysfunction, decreased libido, and impotence. 5-milligram finasteride may also make existing erectile dysfunction disorders worse.(11-13)
Higher doses of finasteride also have the potential to temporarily impact fertility. A comparative study of the semen of 5-milligram finasteride users and a control group found that this drug can reduce sperm count, semen volume, sperm concentration, and sperm motility. However, most of these issues went away once the men stopped taking the drug.(14)
When women have taken the 5-milligram daily dose of finasteride, they’ve reported a range of different symptoms, including:
- Increased body hair growth
- Gastrointestinal discomfort
- Changes to their menstrual cycle
- Decreased libido
Out of all of these symptoms, decreased libido and headaches seem to be the most common. These side effects seem to occur in about 2 percent of female finasteride users.(6)
Are the Side Effects of Finasteride Permanent?
Finasteride side effects aren’t usually permanent. However, people may have a higher likelihood of long-term side effects if they’ve been taking the drug for a while. The time it takes to recover is also dependent on the dose they’ve been taking and the user’s age. Younger individuals (under 40) seem to be more prone to long-term side effects.
A small percentage of finasteride users are affected by side effects that linger even after they’ve stopped taking the medication. This condition, known as post-finasteride syndrome, may be permanent or take a long time to recover from. Long-term side effects, like persistent erectile dysfunction, are also more likely to affect men who already had experienced sexual dysfunction prior to taking this medication. (6,7)
What Is Post-Finasteride Syndrome?
Post-Finasteride Syndrome (PFS) is defined as having one or more side effects that last for at least 3 months. It was not recognized as a legitimate disorder until 2012, when the FDA made it mandatory to provide a warning on finasteride products in the United States, informing users that there may be persistent symptoms. Despite this, whether or not PFS is a true disorder remains a controversial topic. (2)
The psychological symptoms associated with PFS can lead to suicide. Currently, 18,200 people have experienced adverse effects related to finasteride. Out of those individuals, there have been 89 reported suicides worldwide to date. (15)
While it may be easy to blame finasteride for these serious side effects, the risk of developing PFS may be partially genetic. People with PFS have changes in their genetic expression that are considered to contribute to erectile dysfunction. (16)
Despite PFS’s name, it doesn’t only occur after taking finasteride. It can also occur to people who take dutasteride or use other DHT blockers. Dutasteride is a hair loss treatment that is approved for the treatment of male pattern hair loss in Japan and South Korea. It’s stronger than finasteride, reducing DHT levels by as much as 90%. (7,17)
How Long Until Finasteride Side Effects Go Away?
Technically, finasteride’s side effects should be based on the half-life of the drug and your hormone levels going back to normal. This means that side effects should go away when the drug leaves your system. However, how quickly your hormones can go back to normal is also based on how long you’ve been taking the drug. Taking a 1-milligram dose for about 7 months can cause symptoms lasting almost 10 months after you stop taking the drug. Daily use over 27 months may result in long-term symptoms that last up to 4 years. (2,18,19)
People with PFS may see improvement of their symptoms, but it seems like most people don’t completely recover from this condition. Symptoms may improve over time, but reports of full recovery are rare. (15)
How to Reduce Side Effects of Finasteride
If you’re worried about the side effects of finasteride, you should know that this drug only causes systemic side effects when taken in its oral form. Topical finasteride is being explored as an alternative version of this hair loss treatment. Topical finasteride seems to be effective at treating hair loss but is less likely to cause the unpleasant side effects that occur when taking the oral medication. This is because topical finasteride reduces DHT levels in the scalp without affecting serum levels in the body. (18,19)
Lower concentrations of finasteride (.005%) have reduced hair loss significantly after 6 months of use. Using a topical gel with a 1% concentration resulted in improved hair growth after just 3 to 4 months when it was applied twice daily. (20,21)
Unfortunately, topical finasteride is still not widely available or FDA-approved. But if you prefer the idea of a topical, targeted hair loss treatment, you can try minoxidil. This FDA-approved vasodilator supports hair regrowth by increasing blood flow to the scalp. It’s sold as a liquid serum and a foam, and has none of finasteride’s systemic side effects. (20,25)
Finasteride Temporary vs. Permanent Side Effects
Although finasteride is an FDA-approved drug that’s effective and well tolerated by most individuals, it’s important to consider its potential psychological and physiological side effects. Factors like your age, the duration of time you intend to take this drug for, and any pre-existing conditions you have can make finasteride a potentially risky choice of medication. It has the potential to be quite harmful and can considerably and sometimes permanently reduce a person’s quality of life.
For most people, temporary side effects like low sperm count and loss of libido typically resolve themselves soon after stopping treatment. However, an even smaller percentage of those with adverse reactions see their symptoms continue. Longer-term side effects have the potential to turn into PFS and become debilitating.
Only you can decide if taking finasteride is worth the risk. PFS is still a relatively new diagnosis and remains a very rare condition. Much more research needs to be done to determine who is likely to develop temporary side effects versus the permanent symptoms associated with PFS.
In the meantime, researchers are exploring alternative ways to decrease the risk of finasteride side effects by testing different topical formulations. Topical finasteride may be a much safer and more effective hair loss treatment, given that the drug doesn’t cause systemic side effects when applied directly to the scalp.
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Last updated March 2023