Finasteride vs. Dutasteride in Hair Loss Treatment

Hair loss is a common concern for many individuals, and various treatment options are available to address this issue. Two medications that have gained significant attention in the battle against hair loss are Finasteride and Dutasteride. While both drugs are used to combat androgenetic alopecia, they differ in their pharmacokinetics, mechanisms of action, and overall efficacy. This article aims to delve into the distinctions between Finasteride and Dutasteride, shedding light on their unique characteristics.

It is well known that DHT is the primary hormone that leads to repeated miniaturisation of our hair follicles. DHT is an androgen that is many times more powerful than testosterone, and DHT binds directly to androgen receptors in the human scalp. It is this mechanism that leads to the thinning and eventual dying off of hair follicles, also known as balding.

So with this in mind, it seems (and is) imperative that the root cause (no pun intended) of balding is addressed - DHT levels. Testosterone is converted to DHT by an enzyme called 5-alpha-reductase, and a key piece of any hair loss prevention protocol is ensuring that the conversion of Testosterone to DHT is severely limited. As you can see below, the conversion happens at the final stages of the entire HPT axis in men, and is a critical piece of the puzzle to target to stop balding.

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5-alpha-reductase inhibitors are the way to achieve this, and the 2 best options for this are Finasteride and Dutasteride.

But what are the differences? Let’s look at it now…

Pharmacokinetics:

Pharmacokinetics refers to the study of how a drug is absorbed, distributed, metabolized, and excreted by the body. Finasteride and Dutasteride exhibit differences in their pharmacokinetic profiles that are worth exploring.

Now, whilst I mentioned 5-alpha-reductase, it’s not just a singular enzyme: it exists in 2 forms: Type I and Type II. Type I is produced primarily in liver and skin and is carried to the prostate via the systemic circulation. Type II is the major form in the prostate. Research has shown that it is Type II that is most important in hair loss.

Therefore, Finasteride is a type II 5-alpha-reductase inhibitor, primarily metabolised by the liver. It has a bioavailability of approximately 65%, with a peak plasma concentration reached about 2 hours after oral administration. The drug's absorption is not affected by food, making it a convenient option for users. Finasteride, from the research, seems to block around 70% of conversion from Testosterone to DHT.

Dutasteride, on the other hand, is a dual inhibitor of both type I and type II 5-alpha-reductase enzymes. This is likely why serum (blood) levels of DHT can be absolutely nuked when on Dutasteride, because it’s hitting both enzymes and effectively blocking 90-95% of DHT conversion. Dutasteride also has a much longer half-life than Finasteride, contributing to its sustained efficacy. The absorption of Dutasteride is delayed when taken with food, requiring about 4 to 5 hours to reach peak plasma concentration.

Half-lives of Finasteride and Dutasteride:

Half-life is the time required for the concentration of a drug in the body to be reduced by half. Finasteride and Dutasteride differ significantly in their half-lives.

Finasteride has a relatively short half-life of approximately 6 hours. This short duration necessitates daily dosing to maintain therapeutic levels in the body.

Dutasteride, in contrast, boasts a significantly longer half-life of about 4 to 5 weeks. This extended duration allows for less frequent dosing, making it an appealing option for individuals who prefer less frequent medication administration.

This study explored how administration of varying doses of Dutasteride compared to Finasteride, and the half-life effect is very clear. As evident, Dutasteride showed a remarkable ability to crush DHT levels more and for longer as compared to Finasteride.

The dashed line represents the period when all treatment was discontinued. As you can see, Dutasteride over 0.5mg/daily stayed in the bloodstream of participants for far greater than Finasteride, as a result of its significantly longer half-life. It also suppressed DHT to a far greater degree.

Mechanisms of Action:

The mechanisms of action for Finasteride and Dutasteride revolve around their inhibition of the 5-alpha-reductase enzyme, responsible for converting testosterone into dihydrotestosterone (DHT) – a key contributor to hair loss as spoken about earlier.

Finasteride selectively inhibits type II 5-alpha-reductase, predominantly found in the hair follicles and prostate. By doing so, it decreases the levels of DHT in the scalp, mitigating its damaging effects on hair follicles.

Dutasteride, being a dual inhibitor, targets both type I and type II 5-alpha-reductase. This comprehensive inhibition results in a more profound reduction of DHT levels, potentially offering enhanced efficacy in comparison to Finasteride.

DHT Inhibition:

As we know now, DHT is a potent androgen implicated in the miniaturization of hair follicles, leading to hair loss. Both Finasteride and Dutasteride aim to inhibit DHT production, albeit through different approaches.

Finasteride primarily reduces scalp DHT levels by inhibiting type II 5-alpha-reductase. This localised effect helps maintain hair growth in the affected areas while sparing serum DHT levels. Or so the science goes (whether it does stay localised is very much up for debate).

Dutasteride's dual inhibition extends its impact to both type I and type II 5-alpha-reductase, resulting in a more comprehensive reduction of both scalp and serum DHT levels. This broader spectrum of DHT inhibition may contribute to its potential efficacy in hair loss treatment. However, it may also increase the risk of side effects - having both types of enzymes inhibited across the human body may result in more potential widespread systemic effects. Only you and your doctor can make this decision, and it should be noted that Dutasteride is not FDA approved.

Efficacy of Treatment:

The efficacy of Finasteride and Dutasteride in treating hair loss has been extensively studied, with both medications demonstrating positive outcomes.

Finasteride has been a staple in hair loss treatment for many years, with numerous clinical trials showcasing its effectiveness in slowing hair loss and promoting hair regrowth. It is FDA-approved for male pattern baldness and has gained widespread acceptance among users.

Dutasteride, while not FDA-approved specifically for hair loss, has shown promising results in various studies. Some evidence suggests that Dutasteride may be more effective than Finasteride in promoting hair regrowth, potentially due to its broader inhibition of 5-alpha-reductase. In particular, this study showed that Dutasteride outperformed Finasteride in suppressing DHT to a greater degree, with patients having more hair growth (hair count change from baseline) on Dutasteride than Finasteride.

Scalp vs. Serum DHT:

Something that is very interesting is that serum (blood) levels of DHT are not necessarily the best proxy for scalp DHT - these are two very different things.

I often see online, a lot of guys saying:

Dude, I totally just crushed my DHT levels! Look at my blood test, my DHT is near zero! I must be saved from hair loss!

Okay, admittedly, it’s not always exactly like that, but you get the idea. Some men online are equating their lower serum (blood) levels of DHT as evidence that their scalp level of DHT must be as equally low. Yet, these are 2 different beasts. In this study, you can see that even though 0.5mg of Dutasteride (the usual recommended daily dose for most men) lowered the participants’ blood levels of DHT by 92%, this did not equate to the same reduction in scalp DHT levels. In fact, 0.5mg of Dutasteride only reduced scalp DHT by 51%.

And what is important, really, is scalp DHT levels. If your scalp DHT is skyhigh, it won’t matter what your blood level is - that DHT in your scalp tissue will be eating away at your hair and balding you if you are so genetically predisposed.

So, the idea is to combat scalp DHT levels. This is the key. This is why products like RU58841 and pyrilutamide (androgen receptor antagonists/antiandrogens) are so promising, because the idea is that they can bind to androgen receptors in the scalp and stop scalp DHT molecules from binding to hair follicle androgen receptors and accelerating hair loss. I speak about RU58841 in this article, if you are interested in learning more.

In conclusion, the choice between Finasteride and Dutasteride in hair loss treatment depends on various factors, including individual preferences, tolerability, and the desired frequency of medication administration. While both drugs share the common goal of inhibiting DHT and promoting hair growth, their differences in pharmacokinetics, half-lives, mechanisms of action, and efficacy may influence the decision-making process for individuals seeking an effective solution to combat hair loss. Consulting with a healthcare professional is essential to determine the most suitable treatment plan based on individual needs and considerations.

If you are interested in working with me, see the coaching link above.

-The Fitness Doc.