Finasteride Revisited

Finasteride is a medication commonly prescribed by urologists and dermatologists for symptomatic prostate enlargement and male pattern baldness, respectively. Several years ago when I was using Dragon Dictation to help compose patients’ notes for electronic medical record documentation, my dictation of “finasteride” was misinterpreted by the Dragon system as “for a nasty ride.” In complete contradiction to the implied meaning of that dictation error, finasteride, and its cousin medication dutasteride are highly beneficial multiple-use medications that can promote urological and dermatological “smooth sailing.” I often refer to finasteride as Fountain of Youth in a pill. 

The backstory of the development of finasteride by Merck is one of the most fascinating narratives in the history of drug development: 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 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 a chemical that blocked this enzyme, resulting in the same clinical benefits that occurred to the Dominican men, creating the blockbuster medication that was branded as Proscar. 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 They Work

Finasteride and dutasteride work by inhibiting the enzyme 5-ARI (5-Alpha Reductase) that blocks testosterone from being converted to its activated form 5-DHT (5-Dihydrotestosterone) that is responsible for benign prostate growth and male pattern baldness. With 5-DHT levels suppressed, the prostate gradually shrinks in size and hair regrowth slowly occurs.

So Many Uses

Finasteride 5 mg or Dutasteride 0.5 mg are commonly used to improve the symptoms of benign prostate growth (BPH). They slowly and gradually chip away at the size of the prostate, which hopefully results in symptomatic improvement and avoidance of prostate surgery. It will typically take a minimum of 6 months or so before clinical improvement is noted. I tell patients that these medications aim to perform a “medical” TURP (transurethral prostatectomy). In theory, by shrinking the benign prostate growth, it will facilitate the discovery of a prostate nodule or irregularity on digital rectal exam that might indicate an underlying prostate cancer.

A truly spectacular benefit of these medications is a 30% risk reduction in prostate cancer, the #1 most common cancer for men. This is particularly advantageous for men with a strong family history of prostate cancer or those who have had prostate biopsies with pre-cancerous findings. These pre-cancerous biopsies include high grade prostate intraepithelial neoplasia and atypical small acinar proliferation. Some urologists use finasteride or dutasteride for patients with low risk Gleason 6 prostate cancer who are managed with active surveillance.

One’s prostate specific antigen (PSA) laboratory test on these finasteride or dutasteride will typically drop to 50% of baseline, so one needs to double their PSA to see what it would be if they were not taking these medications. Finasteride and dutasteride can function as a “stress test” for a PSA elevation. If the PSA does not decrease 50%, it can spell trouble and point to the possibility of an underlying prostate cancer.

Many men with blood in the urine (hematuria) are found to have BPH as the underlying cause. As the prostate grows, so does the blood supply and with straining to urinate and the high bladder pressures commonly seen with BPH, it is not uncommon for bleeding to occur. Finasteride and dutasteride are highly effective at managing bleeding of prostate origin.

Finasteride at a lower dose (1mg) is used for male pattern hair loss, as opposed to the 5 mg dose used for BPH. It works best for thinning hair of the crown (vertex) region as opposed to the temple region. Initiating the medication before baldness becomes extensive results in the best hair restoration results. Finasteride will also prevent further hair loss. Yours truly in the 1990s was noted to have a sunburn on his crown with definite hair thinning and has used finasteride for over 25 years with complete success in re-establishing a full growth of hair and eliminating sunburn issues. When the Veterans Administration study demonstrated a substantial risk reduction for prostate cancer, it became a no-brainer to use this medication on an indefinite basis since his father and grandfather were diagnosed with prostate cancer. I use a pill cutter to divide a 5 mg finasteride pill into 4 pieces each of which are 1.25 mg. It is clinically and cost-effective.

Of note, finasteride is at times used off label for female hair loss.

Drug Combos

In 2010 the FDA approved Jalyn, a single-capsule combination of dutasteride (0.5 mg) and tamsulosin (0.4 mg) to treat symptomatic BPH in men with an enlarged prostate. The dutasteride shrinks the prostate, while the tamsulosin relaxes the prostate muscle tone.

In 2022 the FDA approved Entadfi, a daily capsule that combines 5 mg finasteride with 5 mg tadalafil (Cialis) for the treatment of urinary tract symptoms related to BPH. The finasteride shrinks the prostate, while the tadalafil relaxes prostate muscle tone.

Side Effects

These medications diminish the volume of semen. For most men this is not a big deal. On rare occasions, they can give rise to 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.

Dosing Flexibility

The usual dose of Finasteride for urological purposes is 5 mg and for hair loss is 1 mg daily. However, any dose used – whether 1 mg, 2.5 mg or 5 mg – can be beneficial, and daily dosing is not an absolute requirement.

Bottom Line: Finasteride (Proscar and Propecia) and dutasteride (Avodart) shrink the prostate gland, can improve lower urinary tract symptoms, diminish the need for prostate surgery, help control prostate-origin bleeding, and offer a significant risk reduction for the #1 cancer in men. They can be highly effective at restoring hair loss as well. They are truly exceptional medications, are generic and inexpensive, and it is no wonder that many urologists themselves avail themselves of these medications.