10 Reasons Why Finasteride is the Best Drug. Ever.

Andrew Siegel MD   1/14/2023

When I refer to finasteride, I also refer to its cousin — dutasteride — both members of the 5-alpha reductase inhibitor class of medication.  I am focusing on finasteride because it was the first in its class and happens to be the medication that I have been taking for many years.

When I attended my 15-year medical school reunion, I first noticed (in the fancy 3-piece mirror in a Chicago hotel) the thinning hair on my crown.  I was not happy about this.  A few weeks later, I was told by both my wife and my father (in the same week) that I had a sunburn on my crown.  This sat poorly with my vanity. Shortly thereafter, I started myself on Rogaine (minoxidil) spray. Unfortunately, it proved ineffective in remedying the situation. Plan B was finasteride (Propecia).  Within a few months, the balding process started reversing itself and ultimately I had complete regrowth of the hair on my crown. Youth restored! Too bad it didn’t help the gray hair that would emerge later.

The Prostate Cancer Prevention Trial that was conducted in the 1990s concluded that finasteride conferred a 25% risk reduction for prostate cancer. I thought that was impressive considering that prostate cancer is the number one cancer in men. How many medical specialties can boast that they have a medication available that can actually prevent cancer? I happen to have a strong family history of prostate cancer (involving my father and grandfather) that clearly increases my risk for the disease. When I thought about a medication that could lower my risk for prostate cancer as well as having already successfully replenished my head of hair, I became convinced that finasteride was an awesome drug.  

Yet, this class of drug confers so much more than these two benefits, offering multiple advantages.  Finasteride and dutasteride are as versatile as Swiss Army knives, powerful tools that can handle an array of problems.

Finasteride and dutasteride are the Swiss Army knives of medications, with at least 10 utilities

10 Reasons Why Finasteride is the Best Drug Ever

  1. It reduces the risk for prostate cancer, the #1 male cancer.

2. It reduces the chance of prostate cancer developing in men with pre-cancerous prostate biopsies (HGPIN–high grade intra-epithelial neoplasia and ASAP–atypical small acinar proliferation).

3. It is a useful adjunct to men on the active surveillance protocol for low risk prostate cancer to help prevent progression to a higher grade and conversion to active treatment.

4. Since it reduces prostate specific antigen (PSA) by 50%, if the PSA is not appropriately reduced, it can spell trouble and point to the possibility of an underlying prostate cancer. This class of drug clearly increases the sensitivity, specificity, and ability of PSA to detect prostate cancer. An important caveat is that men on this class of drug need to have their PSA doubled to account for what the PSA would be in the absence of using the medication.

5. It changes the natural history of benign prostate hypertrophy (BPH) by inhibiting the stimulus to prostate growth, slowly and gradually shrinking the prostate, as opposed to of the other BPH medications can effectively improve symptoms, but are mere Band Aids, not affecting prostate size. As a result, it improves the annoying lower urinary tract symptoms that result from BPH and reduces the need for surgical intervention for BPH.

6. It is useful to treat prostate-origin bleeding, the leading cause of blood in the urine (hematuria) in the aging male.

7. It is useful to treat blood in the ejaculate in men who have chronic hematospermia.

8. It promotes scalp hair growth and helps prevent further hair loss, so is useful for male pattern baldness. (It is also used off label for female pattern baldness).

9. Since it reduces the size of the prostate by reversing the BPH process, a prostate nodule or irregularity is theoretically easier to diagnose on digital rectal exam.

10. When a prostate biopsy is performed on a prostate that has been reduced in size from finasteride treatment, the smaller sized gland with shrinkage of benign tissue will result in a higher yield for finding a cancer. (Thanks Dr. Martin Goldstein, for pointing this advantage out.)

Backstory of the Development of Finasteride by Merck

This is truly one of the most fascinating narratives in the history of drug development. For the details see The Guevedoces: How an Intersex Genetic Defect Led to a Blockbuster Class of Medicines.  The long and the short of it is that in a small and homogeneous enclave of the Dominican Republic, a cluster of men were identified who were born with a genetic defect causing a deficiency of the enzyme that catalyzes the conversion of testosterone to its activated form. These men were found to never develop the typical benign prostate growth that occurs with aging, nor male pattern hair loss, nor acne. Subsequently, Merck scientists were able to synthesize the chemical that blocks this enzyme, resulting in the same clinical benefits that occurred to the Dominican men, giving rise to the blockbuster medication that was branded as Proscar (finasteride). Proscar was FDA approved for benign prostate enlargement in 1992 and was FDA approved for male pattern baldness at a lower dose in 1997, branded as Propecia. Avodart (Dutasteride) was FDA approved for BPH in 2001.

How It Works (this goes for dutasteride as well as finasteride)

Finasteride is a 5-alpha reductase inhibitor (5-ARI) that blocks testosterone from being converted to 5-dihydrotestosterone (5-DHT), its activated form. With 5-DHT levels suppressed, the prostate gradually shrinks in size and hair regrowth slowly occurs. 

Adverse Effects

These medications will diminish the volume of semen present in an ejaculation. For most men, not a big deal. On rare occasions, these medications can cause nipple sensitivity, gynecomastia (man boobs), and sex drive/erectile dysfunction issues.  They do not decrease testosterone levels, and in fact typically increase testosterone levels by 10% or so, since they block the conversion of testosterone to 5-DHT. I have not experienced any adverse effects of finasteride.

Wishing you the best of health,

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Dr. Andrew Siegel is a physician and urological surgeon who is board-certified in urology as well as in female pelvic medicine and reconstructive surgery.  He is an Assistant Clinical Professor of Surgery at the Rutgers-New Jersey Medical School and is a Castle Connolly Top Doctor New York Metro AreaInside Jersey Top Doctor and Inside Jersey Top Doctor for Women’s Health. His mission is to “bridge the gap” between the public and the medical community. He is a urologist at New Jersey Urology, one of the largest urology practices in the United States.  He is the co-founder of PelvicRx and Private Gym.  His latest book is Prostate Cancer 20/20: A Practical Guide to Understanding Management Options for Patients and Their Families. 

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Video trailer for Prostate Cancer 20/20

Preview of Prostate Cancer 20/20

Andrew Siegel MD Amazon author page

PROSTATE CANCER 20/20 is now available at Audible, iTunes and Amazon as an audiobook read by the author (just over 6 hours). 

Dr. Siegel’s other books:

THE KEGEL FIX: Recharging Female Pelvic, Sexual, and Urinary Health


MALE PELVIC FITNESS: Optimizing Sexual and Urinary Health

PROMISCUOUS EATING— Understanding and Ending Our Self-Destructive Relationship with Food

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