Finasteride vs Dutasteride? Which is better?

A few patients have asked me this question lately, so I thought it was time to answer the question here.

First, the basics… There are multiple different types of hair loss.  Androgenetic alopecia (AGA) is the medical term for male pattern loss both in men and women.  AGA is much more common in men, because it is driven by a hormone called dihydrotestosterone (DHT) which is derived from testosterone.  Testosterone levels are much higher in males than females, leading to a higher incidence of AGA in males. 

Dutasteride and finasteride are both used for hair loss.  Let’s sort out the differences between the two.

Finasteride, name brand Propecia, is a testosterone antagonist or inhibitor called a Type 2 – 5 Alpha Reductase Inhibitor.  It works to prevent the conversion of testosterone into dihydrotestosterone (DHT).  Propecia is FDA approved for hair loss and is available as a 1 mg pill taken daily.  Finasteride has a number of side effects including sexual dysfunction, depression and suicidal ideation and increased incidence of aggressive prostate cancer. 

Dutasteride, name brand Avodart, inhibits both Type 1 and Type 2  -5 Alpha Reductase much more potently than finasteride. It is not FDA approved for hair loss in the US, but is approved for Benign Prostate Hyperplasia in the US and approved for hair loss in other countries. Side effects are similar to finasteride.  Dutasteride is prescribed in varying doses, but at 0.5mg it outperforms finasteride in most head to head studies. However, dutasteride is not FDA approved for hair loss. 

Overall, I rarely prescribe finasteride or dutasteride for AGA pattern loss.   When evaluating purely on efficacy, scientific studies show dutasteride is more effective.  I have a few post-menopausal female patients that take dutasteride for a less common condition called Lichen Planopilaris, but I usually do not prescribe it for pattern AGA because it is not FDA approved for this indication. When evaluating the risk and side effect profile, I professionally and personally think Rogaine (minoxidil) is a safer option than either of these medications.

Here are a few other questions I frequently get regarding these hair loss medications.

Are these medications taken orally or used topically?  These medications are commercially available as oral medications.  There have been studies on topical use, but these are experimental only.

Can women take either of these medications?  Propecia is pregnancy category X, meaning it is contraindicated in women who can become pregnant because it causes feminizing effects on the fetus. It is also contraindicated in breastfeeding women. It also is contraindicated in any estrogen sensitive types of cancer. There are no large studies showing safety and efficacy in women, but some small studies have been promising.  Different doses of finasteride have been studied in women, with a dose of 0.5mg and 2.5mg seeming to be the best mix of efficacy and least side effects. 

What are the side effects of these medications? For males with AGA, Propecia side effects include decreased libido, erectile dysfunction, ejaculation disorders, breast tenderness and depression.  The side effect of depression, suicide and suicidal ideation is a newer finding. There have also been some issues with prostate cancer, with one study showing an increased incidence of aggressive prostate cancer in men taking Propecia.  For females, side effects are not well reported due to the small studies, but irregular menstruation, decreased libido and increased body hair growth have been reported. Because of the risk to a pregnant mother or unborn fetus, patients taking these drugs cannot give blood.

How long will it take to see it work?  Finasteride and dutasteride decrease levels of DHT within 24 hours of taking the first dose.  However, it can take at least 3 months to see regrowth of hair. 

What if I stop taking one of these medications?  DHT levels return to pretreatment levels with 14 days of cessation but it may take a year or more for the hair to revert back to pretreatment levels. Also, there have been rare reports of adverse sexual dysfunction side effects taking awhile to resolve.

Still, I am a huge fan of Rogaine, topical Minoxidil.  I think it is a simpler and safer method for hair regrowth.  If you would like to learn more about Rogaine or androgenetic alopecia see our prior articles.  

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