John R. Tkach, M.D.
300 North Willson, Suite 203B
Bozeman, MT 59715
(406) 587-5442

Propecia (finasteride, 1 mg.) for Male Pattern Hair Loss (Androgenic Alopecia): Risks and Benefits

Patient Information Sheet


Propecia (1 mg finasteride) is a tablet taken once a day that has been shown to have moderate benefit for men who have inherited male pattern hair loss. It does slow down the rate of balding and may nurture some hair regrowth. In my experience, it works better when used in combination with topical Rogaine (minoxidil).

I have been prescribing Propecia since it became available in 1997. I have prescribed it for about 30 men mostly in their 20's and 30's. None has complained to me about side effects. One patient has fathered two children on Propecia. None of my patients has stopped Propecia due to side effects.

So, I was surprised to learn recently (November 2012) from the American Academy of Dermatology that Brian Williams on the NBC Nightly News reported that Propecia has been associated with male sexual dysfunction. That report probably came from a short note in the Journal of the AMA (May 9, 2012 Vol. 307, No. 18).

Studies have been done looking at these adverse effects:

  1. Impotence - inability or limitation in the ability to get or maintain an erection strong enough or of long enough duration to function sexually for intercourse leading to conceiving children.
  2. Decreased Libido - the desire and interest in expressing sexual function.
  3. Decreased volume of ejaculate - the seminal fluid composed of sperm suspended in prostate gland fluid.
  4. Ejaculation disorder - difficulty ejecting semen from the penis at the moment of sexual climax.
  5. Breast enlargement and breast tenderness.

These problems could be important if they interfere with conceiving children or with conjugal life.

The Scope of My Literature Searches (12/12/12):

With permission, I went to the Montana State University Bozeman and did multiple 1/2 - 1 hour MEDLINE literature searches totaling 8 hours over a 6-week period. This is a very powerful tool. I used two search engines. I was able to get full text printouts on most of the articles I found. I also looked for position statements from the manufacturer Merck and the American Academy of Dermatology. There are none as of 12/12/12. I did LexisNexis searches looking for examples of lawsuits over Propecia and Proscar. There were none. This report is a longitudinal search for the development of the treatment and its problems.

About Finasteride:

Sex hormones are all, get this, derivatives of cholesterol. They are all variations on cholesterol. Testosterone (the main hormone made by the testicles, dihydrotestosterone (a major active form of testosterone at the cellular level), and estrogen (the main female sex hormone made in the ovaries) and others are all variations on cholesterol and many can be changed back and forth. For example, the enzyme aromatase converts excess testosterone into estrogen.

A major biochemical conversion in the body is Testosterone -> Dihydrotestosterone. This is accomplished by the action of the enzyme 5 alpha-Reductase Type II. Finasteride binds to the enzyme and blocks that step. Thus finasteride is a 5 alpha-Reductase Type II inhibitor. Finasteride is also a variation on cholesterol. Finasteride's chemical structure is similar to testosterone and dihydrotestosterone.

By reducing the amount of dihydrotestosterone in the prostate gland, it protects against prostate enlargement and the inhibition of hair growth on the scalp, specifically, the hair roots.

The History of Finasteride Use and Side Effects.

Around 1990, doctors were looking for a way to combat the worrisome increase in prostate cancer in men. The prostate is a secretion-producing, walnut-sized gland hidden deep inside the pelvis at the outlet of the bladder. That is the main thing the doctor is checking when he does a rectal exam. Cancer is common in this gland, and it is hard to detect. The rectal exam only allows examination of about 1/3 of the prostate. That's why the PSA lab test is so important.

In addition, most men develop a non-cancerous over growth of the prostate (benign prostatic hypertrophy, BPH) between ages 50-70years. It makes it hard to pee. It was hoped that some men could avoid or postpone prostate surgery by using Proscar.

Concerns about prostate cancer, BPH, and treating male pattern hair loss were the concerns that lead to the development and marketing of finasteride (Propecia and Proscar).

Around 1990, researchers found that a new drug finasteride could reverse BPH. They had hoped it would prevent prostate cancer but, sadly, it did not significantly do that. They noticed increased scalp hair growth in some of those men taking Proscar for BPH. By 1997, doctors were getting more experience with finasteride, and Merck started marketing it for male pattern hair loss.

In 1997, it was claimed that these drugs were entirely safe and had no adverse effects. By 2003, articles were being published reporting adverse sexual side effects in a small percent of men taking this drug. At first, it was felt that the risk was so small, it was not worrisome. Patients were advised to continue using them unless they had trouble. About 2% had enough trouble with side effects that they discontinued finasteride.

For a long time, it appeared that the side effects improved in the 2nd and 3rd years of use. The effectiveness of Propecia for hair loss reversal was 48% in the first year and 60% in the second year. As time went along, that percentage went up. It was similarly effective for BPH. It was effective, had few side effects, and we were excited.

But, when millions of people use a drug, side effects start to show up that did not show up with a few thousands in the trial studies. A study published in 2008 placed the estimate of impotence from finasteride at 5-8%, but some studies placed that as high as 38%.

The problem in my opinion was that finasteride was so good for BPH and hair loss that we did not want to curtail its use. That's just my guess.

It got worse. Irwig and Kolukula reported in the Journal of Sexual Medicine (2011, 8::1747-1753) that 94% of men developed low libido (sexual drive). 92% developed erectile dysfunction. 92% developed decreased sexual arousal. 69% developed problems having orgasm, ejaculation. There is one study that showed the sperm concentration in semen went up compensating for decreased volume of ejaculate. Thus fertility was not impaired.

In another study by Irwig, July 2012 (J Sex. Med. doi: 10.1111/j 1743-6109.2012.02846.x) reported that previous studies showed that 20% of patients on Propecia had persistent sexual dysfunction for more than 6 years. He expanded the symptoms to include trouble with cognition (thinking).

Initially it was reported that these sexual problems were temporary and cleared up after 4-6 months off the drug. Recently there are reports that sometimes the effects are permanent and do not clear up off the drug.

More disturbingly, he is now claiming that 89% of subjects had sexual dysfunction and that persistent sexual side effects to Propecia occurred in 96% of the 89% of subjects.

If you decide to use Propecia, please watch for the first 4 side effects I listed at the top. I was not impressed by the documentation for breast enlargement or tenderness.

Saving Money:

Both Propecia and Proscar are finasteride. The Proscar is 5 mg per tablet and Propecia is1 mg per tablet. Some people have found it much cheaper to use the 5 mg Proscar and cut it into fourths. That comes to 1.25 mg per quarter Proscar. In developing the 1 mg size dose for Propecia, a variety of doses were tried. I think this dose should be okay. If you want to try that, let me know so I can write the prescription that way.

Position statement:

What is the truth here? Is the risk of adverse sexual side effects from Propecia 1%, 5%, 8%, 30%, 69%, 89%, or 96%? There appears to be a growing trend in the literature to cause more and more concern. Is it valid or scare tactics? Why is it so hard to get a straight answer? Does Propecia cause infertility? If finasteride really causes these problems, why is it that taking 5 times (Proscar) the Propecia dose does not increase side effects? Many studies were done in rats at 70 times the human dose. Does that really apply to humans at normal doses? There is no question that finasteride is effective. The question is whether it is safe.

I have read this information on Propecia (finasteride, 1 mg.) risks and benefits. I understand the complications and do agree to my using this medication or a generic variation.


Date / Patient's Signature

Keywords: finasteride, Propecia, Proscar, 5 alpha- reductase Type II, adverse sexual side effects, androgenic alopecia, male pattern hair loss.


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The information provided in these patient information sheets is offered for general informational and educational purposes only; it is not offered as and does not constitute medical advice. In no way are any of the materials presented meant to be a substitute for professional medical care or attention by a qualified practitioner, nor should they be construed as such.

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