Introduction
You’ve probably heard about finasteride, but what about dutasteride? The two sound similar enough by name but are they both as effective? Safe? In this blog, we’ll investigate the differences between finasteride and dutasteride and how dutasteride stacks up to the tried and true.
If you’ve taken the time to read our other pieces, you’re likely familiar with the current state of the field when it comes to hair loss treatments—but just in case, we’ll get you back up to speed.
What is dutasteride?
As far as FDA-approved treatments go, minoxidil and finasteride lead the way as the only two medications currently approved for the indication of treating hair loss. (We’ve covered the history and development of both minoxidil and finasteride here and here, respectively.) In the space beyond formally-approved treatments for androgenic alopecia and other forms of pattern hair loss, there exist numerous supplements, nutraceuticals, and medical devices that make use of low-level lasers to exert a therapeutic effect.
Hair loss is neither a new condition—nor is it going away anytime soon—yet there hasn’t been any new FDA-approved drugs for hair loss since finasteride received approval for the indication in 1997. It’s hard to believe that pharmaceutical companies would rest on their laurels with a potential customer base eager and waiting for new and improved methods to fight hair loss, begging the question: Are any compounds on the radar when it comes to future approval for the treatment of pattern hair loss?
What is dutasteride currently approved for, and where is it approved as a treatment for hair loss?
Similar in structure and developmental background, dutasteride, like finasteride, is a compound originally developed to treat issues with benign prostatic hyperplasia (BPH). Both work by targeting the enzyme 5α-reductase that converts the androgen testosterone into the more potent dihydrotestosterone (DHT), which contributes to the shrinkage of hair follicles and thinning of hair on the scalp.
Dutasteride—currently branded as Avodart—is currently only available for the treatment of BPH. In 2011, GlaxoSmithKline (GSK), the patent holder for Avodart, sought additional FDA approval for dutasteride to reduce the risk of prostate cancer.
During the clinical trials, some data suggested that because of the significant reduction of prostate cancer only in less severe presentations, rather than in aggressive forms of prostate cancer. Additional concerns were raised by the FDA that even though dutasteride reduced the overall prevalence of prostate cancer in trial participants by 22.8% over 4 years, a second pass at the trial data appeared to suggest that dutasteride increased the incidence of high-grade presentations of prostate cancer by 0.5%. This data not only caused the FDA to deny the application for an indication of reducing the risk of prostate cancer, but to issue a warning on the label that mentioned this potential risk. Since then, subsequent data over a longer window of time appears to suggest that the concern over finasteride and dutasteride contributing to a higher incidence of high-grade prostate cancer may have been premature; however, this fails to change the fact that dutasteride has yet to receive FDA approval for the treatment of pattern hair loss, approval that was granted to finasteride nearly 25 years ago.
Revisiting finasteride
Given that dutasteride is a chemical analogue of finasteride, both compounds target similar structures and act in comparable ways. Let’s briefly revisit what finasteride is, how it works, and build from there to understand how dutasteride may represent a different avenue for treating androgenic alopecia.
Finasteride is a prescription drug used to treat two separate, but related, conditions in men:
- Benign prostatic hyperplasia (BPH), or an enlarged—but non-cancerous— prostate.
- Androgenetic alopecia (AGA), or male pattern baldness.
Alongside minoxidil, finasteride is one of the two FDA-approved treatments for hair loss. While finasteride is the generic name for the compound, it’s commonly marketed under the brand names Proscar and Propecia for the treatment of BPH and AGA, respectively.
As a drug, finasteride falls within the class of drugs known as 5α-reductase inhibitors (5-ARIs), which work by inhibiting one or more of the three forms of the enzyme 5α-reductase. Inhibiting 5α-reductase disrupts its ability to convert the androgen testosterone into dihydrotestosterone (DHT), the potent androgen that causes follicle miniaturization and hair loss. For this reason, 5-ARIs are also commonly known as DHT blockers.
When used to treat androgenetic alopecia, finasteride is taken orally in tablet form at a dose of 1mg once daily. For the treatment of BPH, the dose is 5mg once daily.
How does finasteride work?
As we’ve mentioned before, finasteride achieves its effects by inhibiting the activity of types 2 and 3 of the enzyme 5α-reductase. As a similar compound, dutasteride not only inhibits types 2 and 3 of the enzyme, but type 1 as well. Given that this isozyme isn’t inhibited by finasteride, the possibility exists that dutasteride could represent a more effective treatment at addressing pattern hair loss than finasteride.
Because 5α-reductase converts testosterone into DHT, and because DHT causes hair follicles to miniaturize and thin the hair strands they produce, inhibiting the activity of 5α-reductase means that less DHT ends up being produced. Less DHT means less follicular miniaturization, and less miniaturization means less hair loss. When using finasteride daily, early results can be seen in 3-4 months, but because of the nature of the hair growth cycle and the length of hair you’re trying to replace, full results may be seen near the one year mark.
Given that dutasteride has yet to see FDA approval for the treatment of hair loss—and exacerbated by the Phase 3 data from GSK’s clinical trials to gain approval for the indication of treating androgenic alopecia—the number of studies investigating dutasteride’s efficacy remains somewhat limited.
How do finasteride and dutasteride compare in terms of inhibitory potency?
Separate from hair loss, trial data has hinted that dutasteride may be more potent than finasteride at preventing the accumulation of DHT in the human body. When it comes to measuring how effective each compound is at inhibiting 5α-reductase, a 2003 study from GSK suggests that dutasteride is not only three times more potent than finasteride at inhibiting 5α-reductase type 2, but 100 times more potent at inhibiting 5α-reductase type 1. Two cited studies suggest that 0.5mg/day of dutasteride could yield a reduction in scalp DHT levels by 51%, while 5mg/day of finasteride reduced DHT levels by 41%. If DHT levels can be taken as a proxy for the likelihood of hair loss, then milligram-for-milligram dutasteride appears to exceed the efficacy of finasteride.
A meta-analysis of 23 studies that compared the effect of different dosages of minoxidil, finasteride, and dutasteride on hair regrowth led the authors to conclude that at 24 weeks, 0.5mg/day of dutasteride represented the most efficacious treatment for an overall increase in total hair count; at 48 weeks, 5mg/day of finasteride represented the best solution for total hair regrowth.
Some studies have begun to investigate the use of antiandrogens in treating female pattern hair loss, but the results and side effects remain mixed. Regardless, finasteride remains unapproved for the treatment of pattern hair loss in women, while dutasteride remains unapproved for the treatment of pattern hair loss in both men and women.
Why do 5α-reductase inhibitors like dutasteride need to be handled safely, particularly by children and pregnant women?
Because it works on male sex hormones, finasteride isn’t approved for use in women—the same can be said for dutasteride. It’s even recommended that pregnant women avoid handling finasteride tablets and dutasteride capsules at all: Though both tablets and capsules are covered in a protective coating, both of the active molecules can potentially be absorbed through the skin if the integrity of the coating is compromised. Why?
We typically associate hormones with sex-linked developmental changes, but androgens like testosterone and DHT are just but one class of hormones. In more general terms, hormones are signaling molecules that communicate and coordinate between different organs and tissues in the body as part of the endocrine system. During pregnancy, levels of different hormones can help lay out the blueprint for the body plan of the developing fetus by modulating certain genes, turning them up, down, on, or off.
As signaling molecules, testosterone and DHT exert their effects by impacting the transcription of many different genes within the chromosomal DNA. In a developing male fetus, the presence of these androgens signals that the undifferentiated sex organs and genitalia of the fetus should develop into those of a male. The absence of those androgens—either due to the original genetic blueprint from a genetically-female fetus, or because certain androgens produced by a genetically-male fetus are being inhibited via a 5α-reductase inhibitor like finasteride or dutasteride—signals that the fetus should instead proceed to develop as a female.
Can dutasteride be used off-label?
If you’re an avid reader of our blogs, you may be thinking: Dutasteride was approved for the indication of treating BPH, so even if it wasn’t approved as a recognized treatment for hair loss, can my doctor still prescribe it to me off-label? The answer is yes.
Based on clinical data provided, dutasteride received approval to be marketed as a treatment for hair loss in both South Korea (2009) and Japan (2015) by the respective regulatory authorities in each country.
While approval for that additional indication of treating hair loss hasn’t passed by the FDA, keep the following in mind:
- Dutasteride has already passed FDA muster for safety as part of the approval process for the treatment of BPH.
- The results published in the scientific literature regarding the usage of dutasteride for treating androgenic alopecia are compelling enough to warrant usage at the discretion of a prescribing doctor.
Given the previously agreed-upon safety profile of dutasteride, coupled with the emerging science, medical practitioners may feel comfortable prescribing dutasteride off-label for the treatment of hair loss in men. Though every patient is different, it remains substantially less likely that antiandrogens like finasteride and dutasteride will represent a viable alternative when it comes to treating hair loss in women.
Is dutasteride a viable option for treating pattern hair loss?
It would indeed appear that dutasteride may be a useful alternative to treat androgenic alopecia, despite having yet to garner FDA approval for that particular indication. Though this line of reasoning can’t be applied to all drugs in all circumstances, it’s worth keeping in mind that just because a drug analogue like dutasteride hasn’t received FDA approval, there’s a difference between having yet to receive FDA approval and failing to receive FDA approval. It remains possible that GSK could seek approval from the FDA to market dutasteride as a treatment for hair loss, following the same path as minoxidil and finasteride in seeking approval for secondary indications.
This doesn’t necessarily mean that dutasteride comes without its share of risks, however. Potential side effects from antiandrogens like dutasteride can include the following:
Given that dutasteride represents a far more potent 5-ARI than finasteride, it could be that dutasteride possesses a higher incidence of severe side effects than finasteride. If these side effects concern you as you begin your hair loss journey, it may be worth checking out additional options that don’t interfere with the endocrine system—our ProCelinyl™-based products like Revela’s Hair Revival Serum or The Growth Concentrate are an excellent place to start!
