Propecia, the 1mg finasteride pill approved by the FDA to treat hair loss, may be far stronger than necessary. Numerous studies have shown doses as low as 0.2mg reduce DHT by the same amount as the prescribed 1mg tablet. So is such a high dose necessary to prevent hair loss? Is there a lower risk of side effects when taking a lower dose? In this article we’ll take a look at what the optimal finasteride dose for hair loss prevention is.
Propecia: the 1mg finasteride pill
The current understanding of androgenetic alopecia (male pattern hair loss) is that the hormone dihydrotestosterone (DHT) binds to hair follicles, causing them to shrink and eventually stop producing hair.
Finasteride inhibits the enzyme 5-alpha reductase, which is what converts testosterone into DHT. No 5-alpha reductase = no DHT.
And in 1997, finasteride was approved by the FDA to treat male pattern hair loss.
But hair loss wasn’t the first medical condition finasteride was approved for. Five years earlier the drug was approved for the treatment of benign prostatic hyperplasia (BPH). The dose approved for BPH – 5mg – was marketed under the name Proscar.
The finasteride dose approved for hair loss was much lower: 1mg. This formulation was given the brand name Propecia.
In the original trials for Propecia, the 1mg dosage was found to result in a “significant net increase in hair count” after 12 months. As far as side effects were concerned, the trials found:
“Finasteride 1mg/d in the treatment of [male pattern baldness] has been well tolerated, with a low incidence of drug-related adverse effects, chiefly in the area of sexual adverse events.”
Since then, there have been many reports of negative side effects resulting from Propecia use. For more information, read The Truth About Finasteride Side Effects.
Since the initial approval of Propecia, the 1mg dosage has been challenged. This is due, in part, to increased reports of side effects. What’s more, some studies have shown that lower doses of finasteride have just the same effect on DHT levels.
Finasteride dose response
Even before Propecia and Proscar were approved, there was already strong evidence that DHT inhibition did not vary much in response to finasteride dose.
This study from 1990, for example, tested dosages ranging from 0.04mg to 100mg.
Part 1 of the study tested daily doses of 25, 50, and 100 mg for 11 days. Part 2 of the study tested doses of 0.04, 0.12, 0.2, and 1.0 mg for 14 days. These tests revealed:
“Results from part 1 showed a significant reduction in dihydrotestosterone (DHT) at all doses and a significant increase in both testosterone (T) and delta 4-androstenedione at the 50- and 100-mg doses. […] Results from part 2 again showed significant reduction in DHT at all doses. […] The DHT metabolites and androstanediol glucuronide and androsterone glucuronide were significantly reduced at all doses. […] In conclusion, finasteride is well tolerated by normal volunteers and results in significant suppression of serum DHT at all doses tested.”
What these trials did find, however, was that the length of time before maximum DHT inhibition was achieved did vary according to dose. For example, a high dose of finasteride would lead to a significant reduction in serum DHT levels almost immediately. Smaller doses led to a cumulative decrease in serum DHT, eventually resulting in similar DHT levels to higher doses:
“After treatment, DHT levels decreased in each active treatment group, but the rate of decrease was dose dependent. No significant change occurred in the placebo group. Maximum suppression occurred rapidly in the 1.0 and 0.2 mg groups and continued throughout the treatment period. In the 0.12 and 0.04 mg groups suppression required increasingly longer to achieve and may not have been complete after 14 days. […] Maximum suppression of DHT occurs after a single dose of 1 mg/day, but equivalent suppression can be achieved in a dose-dependent fashion with lower doses after repeated administration.”
What this research suggests is that doses of finasteride as low as 0.04mg have the same DHT-reducing effects as 1mg or higher – it just takes a little longer to reach the same levels.
So if DHT is suppressed equally by 0.04mg finasteride as the prescribed 1mg Propecia tablet, it could very well be equally as effective at stopping hair loss progression as well.
Subsequent studies revealed similar results. For example, this study recorded the following reductions in scalp DHT levels with varying doses of finasteride:
Could a lower dose reduce side effects?
These studies raise the question of why Propecia is prescribed as a 1mg finasteride tablet when a smaller dose would have the same effect. And this question has been raised in another article in a medical journal:
“As seen in Figure 1, the percent change of DHT for placebo and 0.01-mg Propecia were identical and essentially 0 within a reasonable statistical estimate. The change dropped to 60% for a 0.05-mg dose and stayed that way for all doses up to 5 mg. Thus, a 20 times smaller dose than that recommended had the same effect on the DHT. A similar dose dependence was seen for the serum DHT level (Figure 2); the effect was no different with doses above 0.2 mg.”
It seems clear from the trials cited previously that lower doses of finasteride have more or less the same effect on DHT.
And with many users reporting negative side effects from Propecia, the same article argued that reducing the dose could potentially reduce the incidence of side effects:
“Thus, the fact that the dose has been established by the manufacturer at a level far higher than the level measured as necessary for the inhibition of the conversion of testosterone to DHT has not been reported publicly. Vastly lower doses would likely reduce the chance of side effects.”
However, this seems unlikely in practice.
If a 0.5mg dose of finasteride, say, reduces DHT levels by the same amount as 1mg, then side effects are just as likely to occur. After all, a reduction in DHT is precisely what causes side effects in the first place!
In other words, if two different finasteride doses lower DHT by the same amount, they’ll both cause the same side effects.
Very low doses of finasteride – less than 0.2mg – are likely to reduce the occurrence of side effects in those susceptible. But this is only because such a small dose would not significantly reduce DHT. So whilst side effects would be reduced, so would the benefits for your hair. Because the effectiveness of finasteride lies in its ability to reduce DHT levels, the incidence of side effects is likely to be directly proportional to the benefits for hair maintenance and regrowth.
Is it necessary to take finasteride every day?
So if reducing the dosage has little impact on results or side effects, what about reducing the frequency with which finasteride is taken?
The half-life of a drug is the amount of time it takes for the body to remove half of the dose. For finasteride, this is around five to seven hours. So, if you’re taking finasteride every 24 hours, all traces of the drug are likely to be removed long before your next dose.
But this doesn’t mean it has lost its effect by then, as this journal article reports:
“The terminal elimination half-life (t1/2z) is 4.7 to 7.1 hours; but despite this, slow accumulation occurs with multiple doses. […] A single dose of finasteride suppresses serum DHT levels for up to 4 days, longer than would be expected from the serum terminal elimination half-life (t1/2z) of the drug: this is probably due to the high affinity that finasteride has for the 5 alpha-reductase enzyme.”
It’s important to note that the dosage discussed in this article is 5mg. However, this suggests that taking Propecia every other day – perhaps even every third or fourth day – will have the same effect as taking it every day.
A potential drawback of administering finasteride this way, though, is fluctuations in hormone levels. Taking finasteride every day is more likely to keep levels of DHT and other hormones more stable. If DHT is allowed to creep up for up to four days after medication, these fluctuations could increase the likelihood of side effects.
The best finasteride dose for hair loss
The prescribed Propecia dosage of 1mg finasteride every day undoubtedly works for hair loss.
Increasing this dose is not likely to have an appreciable effect on hair. But nor is it likely to increase the risk of side effects either.
Similarly, evidence suggests that decreasing the dose – even to as low as 0.2mg per day – won’t be any less effective for hair loss. But it probably won’t reduce the incidence of side effects either. You could even get away with taking Propecia every other day – possibly even every four days. As shown, this is not likely to have a significant effect on DHT levels.
But the approved dose for hair loss – Propecia – has been trialled and tested extensively.
In theory, lower doses would be just as effective. But a lower dose does not necessarily reduce the chance of side effects.