Finasteride vs Dutasteride: Which is Better for Preventing Hair Loss?

Dr. Patrick Carroll, MD
Medically reviewed by Patrick Carroll, MD Written by Our Editorial Team Last updated 9/19/2019

Finasteride and dutasteride are two of the most widely known and frequently used 5α-reductase inhibitors available today.

Both drugs are designed to inhibit the conversion of testosterone into dihydrotestosterone — the androgen that causes male pattern baldness. While finasteride and dutasteride share a few key benefits, they’re both unique drugs with slightly different purposes and effects.

In this guide, we’ll compare finasteride and dutasteride as hair loss treatments and look at the main differences between the two drugs.

Finasteride Was Developed and Patented First

Between finasteride and dutasteride, finasteride is the older drug. Finasteride was developed in the 1970s, patented in the 1980s and in 1992 received FDA approval as a treatment for benign prostatic hyperplasia (BPH, or prostate enlargement).

Finasteride was FDA-approved for use as a male pattern baldness treatment in 1997, at a lower dose than the higher-dosed BPH treatment version of finasteride (1mg vs. 5mg).

Dutasteride, on the other hand, was patented in 1996 and in 2001 received its FDA approval as a treatment for BPH. It’s worth noting that dutasteride has not received FDA approval as a treatment for male pattern baldness.

Only Finasteride Is FDA-Approved to Treat Hair Loss in Men

Although dutasteride is approved as a treatment for male pattern baldness in some countries, it hasn’t received FDA approval as a hair loss drug in the United States.

Dutasteride is approved by the FDA, but only as a treatment for BPH. This means that it has 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 hair loss (we’ll cover this subject further down). Dutasteride has been shown to prevent hair loss, but it can only be prescribed for this purpose as an off-label treatment option.

Finasteride Blocks ~70 Percent of DHT, Whereas Dutasteride Blocks 90+ Percent

Studies suggest that dutasteride is more effective at blocking testosterone from converting into DHT — the hormone that causes male pattern baldness.

In a study of 399 patients, researchers found that dutasteride blocked 98.4 percent +/- 1.2 percent of DHT at a 5mg daily dose, compared to 70.8 +/- 18.3 percent with the same dose of finasteride.

This study was conducted on people suffering from prostate enlargement, meaning it used far higher doses of dutasteride and finasteride than the doses used to treat hair loss. Still, it suggests that dutasteride is, milligram for milligram, more effective at lowering DHT than finasteride.

It also showed that dutasteride may be more consistent at blocking DHT than finasteride. The level of variability for the dutasteride group was +/- 1.2 percent, showing an almost total elimination of DHT, with far less variation between patients than the +/- 18.3 percent of the finasteride group.

In simple terms, this means that dutasteride is potentially more effective at blocking DHT and more consistent in its DHT blocking effects than finasteride.

Both Finasteride and Dutasteride Are Effective, but Dutasteride May Promote More Hair Growth

Study data shows that both finasteride and dutasteride are effective at promoting hair growth in men with male pattern baldness. In some head-to-head studies of the drugs, dutasteride increased hair growth in men more than finasteride.

A 2006 study of 416 men aged between 21 and 45 showed that dutasteride produced better hair count results than finasteride over a period of 12 to 24 weeks. 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 helps men to grow more hair than finasteride does. 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 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 four to five weeks in men under 70, while finasteride, on the other hand, has a half-life of around five to six hours in men 18 to 60 years of age (and eight hours in men over the age of 70). 

Of course, this doesn’t mean finasteride isn’t effective at stopping hair loss in men. There are countless studies showing that finasteride works very well at preventing hair loss in both the short term and the long term, and generally, 85 percent of people who use finasteride daily exhibit hair regrowth in the first three to four months.

While there is study data that suggest dutasteride may increase hair growth in men more than finasteride, it doesn’t mean dutasteride is undoubtedly a better option. If you’re looking to grow back your luscious locks, discuss with your doctor what might be the best option for you.

Finasteride and Dutasteride Both Have Side Effects, Though Rare

Finasteride and dutasteride both have side effects, but they’re rare and only affect a very small percentage of users.

In clinical studies, a very low percentage of finasteride users experienced breast tenderness and rashes. Sexual dysfunction was slightly more common — but only marginally.

Specifically, in clinical studies, 1.8 percent of finasteride users experienced a decrease in libido, 1.3 percent experienced erectile dysfunction and 1.2 percent experienced a lower level of ejactulate.

Far as long-term side effects go, although they’re very rare, there have been some reports of sexual side effects that don’t stop even after people stop using finasteride — although it’s also worth noting this is an area of active research. 

Most studies of long-term finasteride use corroborate that long-term side effects are rare. A 1992 study of finasteride resulted in no reports of negative sexual side effects in the 895 men that used the treatment for 12 months, even at a 5mg daily dose.

Over the course of 24 months, the only negative side effects reported were reduced libido and ejaculation issues, which affected approximately one percent of patients.

Other studies show similar results. A 48-week trial of finasteride that involved 212 men resulted in two people experiencing sexual side effects from finasteride, with one person in the placebo group also reporting sexual side effects.

Participants in this study also reported that the negative effects stopped after they stopped using finasteride.

As a whole, the data shows that for most men, finasteride is safe and side effects are rare, reversible and generally not permanent.

Likewise, study data shows that dutasteride is generally safe and well tolerated, even at the higher doses used to treat BPH. Side effects are rare and generally reversible.

It’s important to remember that while side effects from finasteride and dutasteride are rare, they can still happen. If you experience side effects from either treatment, it’s always important to talk to your doctor and let them know about your experience.

Which Is Better for Preventing Hair Loss?

Finasteride and dutasteride are two different drugs with similar effects. Both are thought to prevent hair loss by preventing the conversion of testosterone to DHT. Both are proven to work. Both have rare side effects that, for most users, are tolerable.

Finasteride is the older of the two drugs and is the only one approved by the FDA for the treatment of hair loss in men.

Still, the future looks bright for dutasteride, and it is continuing to be studied as a potential treatment option for male pattern baldness.

Only you and your doctor can decide what treatment is best for you. If you’re concerned about that sneakily receding hairline, talk to your doctor about whether one of these prescription products could be a good option for you.

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This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.