Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 6/21/2021
If you’ve ever looked into medications for treating hair loss, you’ve likely heard of finasteride and dutasteride.
They work by preventing your body from converting testosterone into a different type of androgen hormone called dihydrotestosterone, or DHT.
DHT is strongly linked to hair loss, with research showing that it’s the main hormone responsible for male pattern baldness.
While finasteride and dutasteride both block DHT, there are some medical and legal differences that you should be aware of before you consider using either medication to slow down hair loss and prevent your male pattern baldness from worsening.
Below, we’ve explained what medications like finasteride and dutasteride are, how they work as hair loss treatments and the type of results you can expect from treatment.
We’ve also shared several key differences between finasteride and dutasteride, including each medication’s availability and legal status as a hair loss treatment in the United States.
Finasteride and dutasteride are both medications that block the conversion of testosterone into dihydrotestosterone (DHT) within your body.
Dihydrotestosterone is a type of androgen, or male sex hormone. It’s created as a byproduct of testosterone by an enzyme called 5-alpha reductase.
Only a small amount of your testosterone is converted into DHT, with most of your circulating testosterone left unaffected.
During prenatal development, childhood and adolescence, DHT plays a major role in producing your male sex characteristics.
It’s responsible for everything from your genitals to the body and facial hair that you develop as a teen.
As an adult, DHT is less essential for your everyday wellbeing. However, it still produces certain effects in your body.
If you’re genetically predisposed to male pattern baldness, DHT can bind to androgen receptors in your scalp and cause your hair follicles to gradually stop producing new hairs.
Over time, this can result in a receding hairline, thinning of your hair around the crown (the area at the top of your head) and near-total hair loss.
We’ve explained this process and its effects on your hairline in more detail in our guide to DHT and male pattern baldness.
Finasteride and dutasteride both work by blocking the effects of 5-alpha reductase, the enzyme that converts testosterone into DHT.
By blocking 5 alpha-reductase, these medications reduce DHT levels throughout your body and slow down, stop or reverse the effects that DHT can have on your hair.
Although finasteride and dutasteride work in the same way, there are a few differences between the two medications when it comes to effectiveness, side effects and legal status.
We’ve listed these below, along with more information on how each medication works and what you can expect from each as a hair loss treatment.
Between finasteride and dutasteride, finasteride is the older drug. Finasteride was developed in the 1970s, patented in the 1980s and approved by the FDA in the 1990s, initially as a treatment for benign prostatic hyperplasia (BPH, or prostate enlargement) as Proscar®.
That’s right -- finasteride, the male pattern baldness medication, was originally approved by the FDA to treat BPH.
This is because BPH, like male pattern baldness, is caused by the effects of DHT.
In 1997, finasteride was approved under the brand name Propecia® as a treatment for hair loss in men.
When used for hair loss, it’s prescribed at a lower dose (1mg per day) than the stronger 5mg version that’s used to treat BPH.
Dutasteride, on the other hand, was patented in 1996 and in 2001 received its FDA approval as a treatment for BPH under the brand name Avodart®.
Although research shows that dutasteride is effective at treating hair loss, it hasn’t yet received approval from the FDA as a hair loss treatment.
Dutasteride is approved by the FDA, but only as a treatment for BPH. This means that it’s gone through the FDA’s rigorous testing and research process, but only as a drug marketed with the intended purpose of combating prostate enlargement.
This doesn’t mean that dutasteride isn’t effective at preventing male pattern baldness (we’ll talk about this subject in more detail further down the page).
Dutasteride has been shown to treat and prevent hair loss. However, since the FDA has yet to approve it for this specific purpose, it can only be prescribed as an “off-label” treatment for hair loss in the United States.
Currently, only finasteride is approved by the FDA as a treatment for hair loss. However, studies have largely shown that both medications -- finasteride and dutasteride -- are effective at cutting DHT production and treating male pattern baldness.
In one study published in the Journal of the American Academy of Dermatology in 2014, a team of researchers compared the effects of finasteride vs. dutasteride on 917 men between the ages of 20 and 50 who were at various stages of male pattern baldness.
They concluded that both finasteride and dutasteride were successful at increasing hair growth over a 24-week period, and that side effects were similar among both groups.
It is worth noting that although finasteride and dutasteride were both successful at treating hair loss and promoting hair growth, the researchers concluded that the men who used dutasteride had thicker hair -- and more of it -- after 24 weeks than the men who used finasteride.
A review published in the journal Clinical Interventions in Aging, which featured data from three studies comparing dutasteride and finasteride as treatments for male pattern baldness, came to a similar conclusion.
The researchers concluded that although both medications are effective at treating hair loss in men, dutasteride “seems to provide a better efficacy compared with finasteride” with a broadly similar rate of side effects.
In short, although both medications treat hair loss, there’s some evidence that dutasteride may be slightly more effective.
One reason that dutasteride may be slightly more effective than finasteride is that it appears to block more testosterone from being converted into DHT, the hormone that causes male pattern baldness.
In a 2004 study published in the Journal of Clinical Endocrinology and Metabolism, researchers compared the effects of finasteride and dutasteride on serum levels of DHT (the amount of DHT that’s present in the bloodstream).
After testing a total of 399 patients, they found that a 5mg per day dose of dutasteride reduced DHT levels by approximately 98.4 +/- 1.2 percent.
In comparison, finasteride reduced DHT by 70.8 +/- 18.3 percent when used at the same dosage.
This study was conducted on people suffering from prostate enlargement, meaning it employed far higher doses of dutasteride and finasteride than the amounts typically used to treat hair loss.
Still, it suggests that dutasteride is, milligram for milligram, more effective at lowering DHT levels than finasteride.
It also showed that dutasteride may be more consistent at blocking DHT. The level of variability for the dutasteride group was +/- 1.2 percent, showing an almost total elimination of DHT, while the level of variability in the finasteride group was +/- 18.3 percent.
In simple terms, this means that dutasteride may potentially be more effective at reducing DHT levels and more consistent in its DHT-blocking effects than finasteride.
Study data shows that both finasteride and dutasteride are effective at promoting hair growth in men with male pattern baldness.
However, in some head-to-head studies of the drugs, dutasteride increased hair growth in men more than finasteride.
In one study published in the Journal of the American Academy of Dermatology, which involved a total of 416 men with male pattern hair loss, researchers found that men who used dutasteride experienced a greater percentage increase in hair count than men who used finasteride.
The men given dutasteride received a dose of either 0.05mg, 0.1mg, 0.5mg or 2.5mg each day, while the men who received finasteride received a 5mg dose (approximately five times the dose typically prescribed to treat hair loss). The study covered a period of 24 weeks in total.
The researchers used an expert panel and before and after photographs to compare and verify the effects of the two drugs.
There are a few theories as to why dutasteride has a stronger effect on hair growth in men with male pattern baldness than finasteride.
One reason could be that dutasteride’s stronger effect on blocking DHT makes it more effective as a treatment for preventing male pattern baldness.
Another reason could be that dutasteride has a longer half-life, meaning it stays in the body for longer than finasteride after it’s taken.
Dutasteride has a half-life of approximately five weeks, meaning a single dose of dutasteride is capable of remaining in the body for several months.
Finasteride, on the other hand, has a half-life of approximately five to six hours in men aged 18 to 60 and eight hours in men 70 and older.
This means that a typical dose of finasteride lasts for a significantly shorter period of time in your body than a typical dose of dutasteride.
Of course, this doesn’t mean that finasteride isn’t effective at stopping hair loss in men. Several studies have found that finasteride produces a reduction in hair loss and, for many men, serious improvements in hair growth.
For example, a series of two one-year trials found that men who used finasteride experienced a clinically significant increase in hair count and a noticeable reduction in hair loss.
A long-term study carried out in Japan, which looked at the effects of finasteride over a 10-year period, also found that it was effective at treating male pattern baldness.
In this study, 99.1 percent of balding men who used finasteride over a 10-year period found that their hair loss stopped during treatment.
91.5 percent of the men experienced improvements in hair growth while using finasteride.
In general, the majority of men with hair loss who use finasteride report that their hair loss either slows down, stops or reverses over the course of several months.
While there is study data that suggests dutasteride may increase hair growth in men more than finasteride, this doesn’t necessarily mean that dutasteride is the better option.
If you’re losing your hair, it’s best to talk to a healthcare provider about the hair loss treatments that are most effective for you.
Because finasteride and dutasteride both work by inhibiting the 5-alpha reductase enzyme and reducing the amount of DHT in your body, they have similar side effects.
The most common side effects of finasteride are:
Inability to get or maintain an erection (erectile dysfunction, or ED)
Problems related to ejaculation, such as a decreased semen volume
A reduced level of sexual desire
Testicular pain or discomfort
The most common side effects of dutasteride are very similar:
Inability to get or maintain an erection (erectile dysfunction, or ED)
Problems with ejaculating
Decrease in sex drive
Although sexual side effects such as these may sound alarming, they’re uncommon and affect a small percentage of men who use medications like finasteride or dutasteride.
In clinical trials, 1.8 percent of men who used finasteride reported developing a reduced level of interest in sex.
Only 1.3 percent experienced erectile dysfunction (ED) during treatment, and 1.2 percent reported experiencing a lower volume of ejaculate.
In clinical trials of Avodart, a common version of dutasteride used to treat BPH, a slightly higher percentage of men reported sexual side effects, such as erectile dysfunction, during the first six months of treatment.
4.7 percent of men who used Avodart reported experiencing erectile dysfunction, with 3 percent reporting decreased libido and 1.4 percent reporting issues with ejaculation.
Many side effects became less common during long-term treatment.
Although uncommon, 5-alpha reductase inhibitors such as finasteride and dutasteride may also cause more serious side effects. These include:
Increased male breast size, or swelling of the breasts and nipples
Lumps, pain and discomfort of the breasts
Discharge from the nipples
Rash, itching, hives and swelling of the face and lips
Difficulty breathing and/or swallowing
These reactions are rare, but may be serious. It’s important to contact your healthcare provider immediately, if you experience any of these side effects after taking either finasteride or dutasteride.
While finasteride reduces overall prostate cancer risk for men, some research suggests that it may be associated with an increased risk of high-grade prostate cancer in older men.
However, analysis has found that this may be linked to confounding factors and detection bias rather than finasteride itself.
In either case, this research is based on the effects of finasteride at a significantly higher dose (5mg) than the typical dose used to treat hair loss.
Overall, studies show that for the majority of men, finasteride is a safe medication and that side effects are rare, reversible and generally not permanent.
Likewise, study data shows that dutasteride is safe and well tolerated, even at the higher doses used to treat BPH. Side effects are rare, often temporary in nature and generally reversible.
Finasteride and dutasteride both work by inhibiting the 5-alpha reductase enzyme and stopping your body from converting testosterone into dihydrotestosterone, or DHT.
By reducing DHT levels, both medications are shown to slow down, stop or reverse the effects of male pattern baldness.
Because they’re so similar, finasteride and dutasteride may cause a similar range of side effects, the majority of which are mild and tolerable.
As the older of the two medications, finasteride is currently the only one approved by the FDA as a treatment for male pattern baldness.
This makes it the obvious choice if you’re looking for an effective, readily-available medication that can stop your hair loss from worsening.
Still, the future looks bright for dutasteride, and it’s continuing to be studied as a potential male pattern baldness treatment option that may eventually become available in the United States.
If you’re concerned about a receding hairline, bald spot or other sign of male pattern baldness, it’s important to talk to a healthcare provider as soon as possible.
Hair loss can worsen quickly. By treating your hair loss as soon as you notice it, you’ll increase your likelihood of maintaining a strong hairline and full head of hair well into your 40s, 50s and beyond.
We offer a large selection of science-based hair loss treatments online, including options such as finasteride and minoxidil.
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