Propecia, as you know has been an FDA approved treatment for Male Pattern Baldness since 1998. It is simply a lower milligram dose of the prostate drug, Proscar, which came out in 1992. The mechanism of action for Propecia/Proscar is its inhibition of 5 alpha reductase type 2. A few years later a dual 5 alpha reductase enzyme inhibiting drug, Avodart was released for the management of prostate enlargement. Studies on the hair growth effects of Avodart revealed it to be slightly superior as compared to Propecia for the treatment of hair loss.

      Proscar, Propecia, and Avodart have all been touted by the medical community as having minimal to no side effects or significant health considerations. The package insert on Propecia states that sexual side effects occur is less than 2% of the users. The last 20 years of studies and side effect reporting has painted a much different, rather ominous picture.

      First consider the ever expanding list of side effects that accumulates in the Physicians Desk Reference with each passing year. In the 1990’s, the only reported side effect was a reduced volume of ejaculate in “less than 2%.” Along the way a somewhat nondescript catch all category of “Sexual side effects,” Gynocomastia (male breast enlargement) and Depression made it on the list of official side effects. 

      Merck, the makers of Propecia, would still have you believe, based on the studies that *they* conducted, or paid large sums to have conducted, that sexual side effects occur in less than 2%. Independent, non-industry sponsored studies have revealed a sexual side effect profile as high as 38% for sexual side effects. The following study in rats and several case studies in humans, suggest that infertility is also likely an issue, with some indicating that infertility may continue to be a concern, even after discontinuing treatment.

Fertil Steril. 2011 May; 95(6):2125.e13-4. Epub 2011 Feb 3.
Finasteride-induced secondary infertility associated with sperm DNA damage.
Tu HY, Zini A.

Division of Urology, Department of Surgery, McGill University, Montreal, Quebec, Canada.

To report a case of low-dose finasteride-induced secondary infertility with associated elevated sperm DNA fragmentation index (DFI) and otherwise normal semen parameters.

Case Report.

University Hospital

A 48-year-old man on low-dose finasteride and his 37-year-old wife with normal menses and normal gynecologic exam.

Determination of sperm DFI and discontinuation of low-dose finasteride.

Sperm DFI.

The sperm DFI done a year earlier was 30%. This value was unchanged when repeated 2 months later. The patient was advised to stop finasteride. Three months after discontinuing the finasteride, the DFI decreased to 21% and subsequent DFI after another 3 months improved to 16.5%. To date, there is still no documented full-term pregnancy or live birth.

The significant reduction in DFI within 3 months of finasteride cessation and continued improvement suggests a causal link between finasteride and sperm DNA damage. We hypothesize that low-dose finasteride may exert a negative influence on sperm DNA integrity, resulting in increased pregnancy losses. We suggest that in infertile men using finasteride, sperm DFI should be measured in addition to semen parameters, and a trial of discontinuation of finasteride may be warranted.

Erectile Dysfunction (ED) has also been a listed side effect since Proscar came on the market, and is easily the most common single sexual side effect complaint. Most we’ve talked to who use Propecia or Avodart have this complaint to varying degrees. ED, even in its mildest forms, can be disasterous to sexual activity. As devastating as ED has the potential to be, Merck still insists on reporting the incidence of this as being less than 2%.

Unfortunately, this study in rats showed that Avodart had a compromising effect on the erectile function of 100% of the rats evaluated. This is certainly more consistent with the feedback which we’ve gotten from Avodart and Propecia users, who almost uniformly report that though they don’t have full blown, diagnosable ED, things don’t feel “quite the same.”

J Sex Med. 2011 Nov;8(11):3066-74. doi: 10.1111/j.1743-6109.2011.02425.x. Epub 2011 Aug 11.
The effects of chronic 5-alpha-reductase inhibitor (dutasteride) treatment on rat erectile function.
Pinsky MR, Gur S, Tracey AJ, Harbin A, Hellstrom WJ.


Department of Urology, Tulane Health Sciences Center, New Orleans, LA, USA.


Numerous clinical series have reported an association between Introduction. 5-alpha-reductase inhibitors (5ARIs) and sexual To further dysfunction, but there are limited preclinical data available. Aim. investigate the mechanisms of erectile dysfunction (ED) related to 5ARI therapy Outcome measures include serum using a rat model. Main Outcome Measures. dihydrotestosterone (DHT), relaxant and contractile properties of cavernosal Twenty adult male muscle, and nitric oxide synthase expression. Methods. 10) and dutasteride = Sprague-Dawley rats were randomized into control (N 10) groups. Serum samples were obtained = mg/rat/day, in drinking water, N (0.5 at baseline, from which DHT was measured after 30 days of treatment via radioimmunoassay (Beckman Coulter, Fullerton, CA, USA). Before the terminal blood draw, erectile response was measured using cavernosal nerve stimulation. The relaxant and contractile properties of cavernosal muscle strips were evaluated in tissue baths, and immunohistochemical (IHC) staining for nitric Mean serum oxide synthase (NOS) and collagen deposition was performed. Results. DHT was suppressed by 86.5% (range 64.2-94.8%) after 30 days of 5ARI treatment 0.0024). In vivo erectile response in the = and was statistically significant (P dutasteride treated group decreased significantly compared with control  (P<0.001). While electrical field stimulation (EFS)-induced and  acetylcholine-induced relaxation was decreased, EFS-induced and phenlyephrine-induced adrenergic contraction was significantly enhanced in the  dutasteride group (P<0.01). IHC studies demonstrated increased collagen  deposition in the treatment arm as well as altered expression of neuronal NOS The 5ARIs, as demonstrated in (nNOS) and inducible NOS (iNOS). these rat cavernosal smooth muscle studies, dutasteride had a detrimental effect on erectile function. Enhanced iNOS expression may protect penile smooth muscle from fibrosis. The effect of 5ARIs on human sexual function warrants further investigation. Pinsky MR, Gur S, Tracey AJ, Harbin A, and Hellstrom WJG. The effects of chronic 5-alpha-reductase inhibitor (dutasteride) treatment on rat erectile function. J Sex Med 2011;8:3066-3074.
© 2011 International Society for Sexual Medicine.

      My obssession with hair is such that I’d personally be willing to gamble with or deal with these side effects if these drugs transformed us from Bruce Willis to Brad Pitt in the hair department, but they don’t even come close. They do stop the progression of hair loss, at least for awhile, in most, and generate a modicum of re-growth in slightly less than half. Avodart *does* work slightly better than Propecia in this regard, but its side effect profile, especially the incidence of Gyno, is more pronounced. I was personally on Proscar from 1992, when it came out, to 2004, when I discontinued due to concerns about its estrogenic side effects. While on Proscar I thought I had no side effects, but when I discontinued I felt dramatically better and my libido skyrocketed within about 5 weeks. Because of the other measures I was using to battle hair loss concurrent with Proscar, discontinuing it fortunately never cost me a single strand of hair.

      This should be enough to dissuade anyone from using these drugs, however, there’s another serious concern. Recent studies from Government-funded Prostate Cancer prevention trials found that although they did reduce the incidence of milder forms of Prostate Cancer, they dramatically increased the risk (12 fold!) of the most aggressive and lethal forms of the disease. 

      Fortunately there are alternatives for both Avodart and Propecia that address the same mechanisms of action and have anti-aging properties as well. The following related article contains links to many other articles that go into detail identifying these side effect free compounds and their mechanisms of action.