A 1mg dose daily is the suggested treatment for male-pattern hair loss. A 5 mg dose is given to treat benign prostatic hypertrophy (prostate enlargement) in men. Some patients quarter a 5 mg tablet with a pill cutter and then take ¼ of a tablet daily to save cost.
Finasteride is being used on postmenopausal women with greater frequency. The usual dose is 2.5 mg daily, but the results aren’t has dramatic as in men. Because it can feminize a male fetus, women in childbearing years cannot use finasteride.
By prescription. Finasteride comes in 2 strengths:
1mg- brand (Propecia) or generic
5mg- brand (Proscar) or generic
Generic versions are now available but beware that the price savings for a 1mg dose may not be as great as with most generics. Hopefully this may change with time. 5mg finasteride tablets are quite inexpensive.
Mode of Action
Finasteride inhibits the activity of Type II 5-alpha reductase, an enzyme that converts the male hormone testosterone into a more potent form called dihydrotestosterone (DHT). DHT is believed to act on scalp hair follicles to suppress them and gradually create weaker and smaller hair follicles. Finasteride will lower the tissue DHT levels by about 66%. It’s half-life in 6-8 hrs.
Scalp hair is rather unique in that it is nonpubertal hair that is not stimulated by testosterone and is thinned by the effect of DHT. Beard and chest hair are stimulated by testosterone and DHT. In these regions, finasteride reduces the density, but this effect is most often not noticed. Finasteride has been occasionally used to reduce body hair in women.
Large, multi-year studies have shown finasteride to reduce hair loss and/or stimulate hair regrowth in a majority of men treated. In a 5-year study, 65% of men with mild to moderate male-pattern hair loss were found to have a positive result (hair loss reduced and/or hair regrowth stimulated). Finasteride therapy must be continued to maintain a positive result. Physician hair restoration specialists often combine minoxidil and finasteride therapy to achieve an optimal result in selected patients. Medical therapy may be combined with surgical hair restoration to achieve and maintain the best result.
Finasteride should not be used or handled by a woman who is pregnant or who may become pregnant. The drug can cause abnormal development in a fetus. Therefore, finasteride should not be used in women of childbearing years.
Reported side effects in men include decreased libido (sex drive), erectile dysfunction, male breast enlargement and psychological depression. To date no significant side effects have been noted in postmenopausal women.
Occasional patients may have side effects continue even after discontinuing finasteride. The frequency of this scenario is controversial with most hair surgeons finding it rare in their patients. Studies are on going to determine the true risk. See Post Finasteride Syndrome (below).
Effects of finasteride can be enhanced by concomitant use of minoxidil. Abrupt stoppage of either drug is usually followed by significant shedding of gained and preserved hair.
Post Finasteride Syndrome (PFS)
In 2011 a sex clinic physician reported on patients found in an on-line blog who reported sexual side effects of Propecia that continued at least 3 months after discontinuing the drug. 71 patients filled out a questionnaire. The statistics were that 94% developed low libido, 92% erectile dysfunction 92% decreased sexual arousal and 69% claimed problems with orgasm. A 2017 article on 16 patients considered to have PFS showed altered levels of neuroactive steroids in their cerebrospinal fluid, possibly a link to depression.
These studies are contrary to the experience of most hair surgeons who have been using Propecia extensively; and this has been the subject of some controversy and confusion. Many of these doctors had never seen permanent side effects in their patients on Propecia. Early studies on Propecia generally showed an incidence of sexual side effects in the range of 2%. A 2017 study of 3177 men showed a 0.7% incidence of side effects while the hair growth continued to improve with negligible problems. In another large study reviewing 17 trials and 17,494 patients, patients being treated for BPH with finasteride and dutasteride showed a statistical increase in sexual adverse events. However, male pattern baldness patients showed no statistically significant sexual problems on these drugs.
Further studies should help clarify the discrepancy in these studies on the frequency of sexual side effects of finasteride.
Prostate Cancer and Finasteride
A large study of 18,882 patients taking finasteride 5mg daily vs placebo showed a 25% reduction in the number of prostate cancers that developed. However, a small subset of the finasteride patients who developed prostate cancer had a higher Gleason number on biopsy.
The Gleason number is a histologic rating of the potential aggressiveness of the tumor cells. At debate is whether or not the Gleason number is as accurate in a destimulated tumor and if the higher Gleason numbers actually correlate with a more aggressive tumor. Also, because finasteride shrinks the prostate by 25%, prostate cancers are more frequently detected. Current thinking is that prostate cancer should not be a deterrent to using finasteride.
Finasteride causes a median 40% decrease in serum PSA in men 40-49 yrs of age, and a median 50% decrease in men 50-60 years of age. Therefore it is important to notify your doctor so that proper adjustments in calculating the PSA can be made.
There is no statistical evidence that finasteride has an effect on sperm count or morphology in a male with a normal sperm count. Some studies suggest a male with pre-existing hypospermia might have a decreased fertility while on finasteride. If this is a consideration, the doctor could order a pretreatment sperm count and motility.