Finasteride (Propecia)

Finasteride is used in the treatment and prevention of male pattern hair loss or androgenetic alopecia. Male pattern baldness, is caused by dihydrotestosterone (DHT), which causes shrinking or miniaturization of the hair follicles that are prone to baldness.  DHT does not generally affect the hair in the back or sides which is known as the permanent zone. DHT is a byproduct of testosterone and is formed by the action of the enzyme 5-alpha reductase. Finasteride works by suppressing the enzyme 5 alpha reductase Type 2, which is responsible for the conversion of most of testosterone to DHT. Finasteride or Propecia, is one of the two FDA approved medications for treatment of male patterned hair loss.


Finasteride is most effective when treating the areas of the scalp that are thinning, however it will not stimulate hair growth in areas that are completely devoid of follicles. The major advantage of finasteride is the ability to help maintain ones’ own hair or considerably slow down the progressive loss of hair related to androgenetic alopecia.

Finasteride is also used for treatment of benign prostatic hyperplasia (BPH) in male adults through the same mechanism since the hormone DHT is also responsible for prostate enlargement.

Increased Volume of Existing Hair – The goal of finasteride is to promote the reversal of miniaturization i.e. increase hair volume and to positively improve the hair count. Studies have shown finasteride is capable of reversing hair miniaturization particularly in young to middle-aged men with androgenetic alopecia, but not in postmenopausal women.

The graph below shows that the maximum improvement from finasteride is expected after one year of using it on average. The results will be sustained then for another one or two years and declines after that. Although patients continue to lose hair after the first 2-3 years of being of finasteride (see the graph: Propecia for 5 years), the loss is much slower when compared with the patients who don’t take finasteride (see the graph: Placebo for 5 years).

Delaying Hair Loss – Finasteride has been shown to delay the loss of native hair which is prone to patterned baldness. Finasteride does not work for everyone and your candidacy should be determined by a physician preferably after a microscopic evaluation of scalp. Once started it should be taken daily for 6 months before evaluating its efficacy. Finasteride cannot completely stop hair loss but it can slow it down in most patients.

Shock Loss Prevention – After any stress whether it is emotional, physical or trauma, we may experience of hair loss. If however, you are genetically prone to balding or have active hair loss currently any stress may exacerbate hair loss even faster. A hair transplant could be stress on the scalp. In order to minimize the shock loss we recommend patients start on Propecia or Rogaine. The best time to start finasteride to prevent shock loss is at least 2 weeks prior to the hair transplant. For optimal outcome, it should be continued for at least 6 months after hair transplant.

Mechanism of Action

The mechanism of action of finasteride is based on its preferential inhibition of the 5alpha-reductase enzyme Type II which inhibits the conversion of testosterone to dihydrotestosterone (DHT). Simply put, finasteride disrupts the conversion of testosterone to the more potent DHT. This decrease in serum and tissue DHT concentrations results in less of an effect on both the prostate and hair follicles which are the primary targets. As a result, interruption of DHT plays a key factor in halting the development of androgenetic alopecia in those patients genetically predisposed.

Finasteride blocking DHT graph

What to Expect

If using finasteride as directed for androgenetic alopecia (male patterned balding) you need to allow at least six months to a year to see optimal results. Some men may experience excess shedding in the first few months of taking finasteride. This shedding should not be mistaken with exacerbation of hair loss and it is always temporary. It is not clear why some patient experience the initial shedding, but it may be due to activation of hair follicles increased turn over. After the first few months, the shedding should subside.

Keep in mind that a visible improvement with finasteride could be seen in only 40-50% of users. However, microscopic improvement could be observed in most patients after the first few months. If you are taking finasteride and you feel your hair loss has not improved within a few months, see your physician before stopping your medication. Your microscopic evaluation may show positive changes that are not evident to the naked eye.

Dosage and How to Use

Finasteride for hair lossThe typical dose of finasteride for hair loss treatment is 1mg by mouth per day. It can be taken any time during the day and it could be taken with or without food. Finasteride 1mg or Propecia is available by prescription for hair loss treatment or prevention.

Finasteride is also available in 5mg tablets which is called Proscar. Finasteride 5mg is prescribed for prostate enlargements (BPH) and should not be taken for hair loss as 1mg dose has been proven to be the optimum dose for that purpose. Some patients cut Proscar (finasteride 5mg) into quarters and take one quarter or1.25mg per day for hair loss treatment. It is not easy to cut the pills to equal quarters but it is more cost effective.

The half-life of finasteride is 4 to 6 hours therefore it is recommended to be taken daily to keep the serum concentrations at a steady state. Having said that, the effect of finasteride may last 5-6 days after stopping it due to the duration of its blocking effect on the 5-alpha reductase enzyme.

Finasteride side effects are relatively rare when taken at the recommended dosage.  Sexual side effects such as decreased libido are expected to be greater if higher doses of finasteride is taken.

Common Side Effects

Finasteride is widely used for hair loss treatment and prostate enlargement. Although it is well tolerated by most men, like any other medication it has some side effects that should be considered before starting to take it.

Decreased libido – Decreased libido aka low sex drive has been documented through the initial studies on Propecia. It is higher than placebo by less than 1%. If the patient experience low sex drive with the Propecia and stop the medication, the side effect should be resolved within a few days. Persistent decrease in sex drive has been reported but not scientifically documented. That is why the company, Merck had to add this to the label of the medication.

Erectile dysfunction – Recent studies have demonstrated that there is no clear evidence of the negative effect of finasteride on erectile function.

Ejaculatory volume – Reduction in ejaculatory volume has been established in a small number of men using it with no effect on fertility or sperm count.

Mood change –  Currently, there is no direct link between 5-alpha reductase inhibitor use and depression; however, several small studies and case reports have led to depression being listed as a side effect on the medication packaging.

Post finasteride syndrome – The phrase “post finasteride syndrome” is established by men in North America about a variety of symptoms that was claimed to be associated with finasteride use. Those symptoms include neurological, hormonal, sexual and psychological symptoms that has been attributed to the medication. Despite the fact that a health advocacy group called the Post-Finasteride Syndrome Foundation was also established to increase awareness and provide support to the patients with those problems, this phenomenon was never properly recognized by scientific community.

Propecia N=945 Placebo N=934
Decreased Libido 1.8 1.3
Erectile Dysfunction 1.3 0.7
Ejaculation Disorder
(Decreased Volume of Ejaculate)
Discontinuation due to drug-related sexual adverse experiences 1.2 0.9

Table 1: Drug-Related Adverse Experiences for PROPECIA (finasteride 1mg) in Year 1 (%) MALE PATTERN HAIR LOSS

Rare Side Effects

There are also uncommon side effects associated with finasteride use. Some of these adverse effects are more scientifically established to be linked to finasteride than others.

Testicular pain – Occasionally patients who have used finasteride report testicular pain. This pain is reversible with discontinuation of finasteride and is one of the rare side effects of finasteride.

Gynecomastia – Enlargement of breast glands in men aka gynecomastia has been reported with finasteride use. Gynecomastia is caused by natural changes in the levels of testosterone that will lead to an increase in estrogen level. Breast tissue enlargement and development is stimulated by estrogen (female hormone) and inhibited by androgen (male hormone), therefore gynecomastia is generally caused by an increase in the ratio of free circulating estrogen/androgen which is what happens with blockage of DHT production. Gynecomastia risk in patients treated with finasteride increases by 1-2%. This condition is not reversible and may need surgical removal of breast tissue.

It is important to note, although there is the small risk of developing gynecomastia in men who take finasteride, there is no relation to an increased incidence of breast cancer when compared to men who never took the drug.

Energy level – Lowering DHT and testosterone can result in andropause aka male menopause. Andropause occurs naturally and gradually as a man ages therefore it may go unnoticed for years.   Fatigue and low energy may be attributed to this drop in hormone level. Although patients who use finasteride do not drop their testosterone level, finasteride causes a drop in DHT that has been claimed to be cause of a lowered energy level. This is not scientifically documented as other side effects of finasteride have through prospective studies.

Persistent sexual side effect – The persistence of sexual side effects appears to be a rare event. It has yet to be determined whether these recent reports represent a true causal relationship, or if they are simply coincidental and related to other factors such as the high incidence of sexual dysfunction by aging, and/or the placebo effect. Also, little data is available concerning the medical and psychological work-up of these patients to exclude other potential factors.

Prostate cancer effects – The impact of finasteride on the prevention of prostate cancer has been discussed extensively in the medical literature. Finasteride is found to be effective in significantly reducing the incidence of low-grade prostate cancer. But the paradoxical increase in high-grade cancer in the finasteride group has been attributed to increased sensitivity and improved performance of prostate specific antigen (PSA) levels ability to detect all grades of prostate cancer.


Males below age 18 – DHT does not have a physiologic role in adult males, however it is essential for maturation of external genitalia in teenagers and children. Thus, finasteride should not be taken by this group.

Women – To date, there are very few studies evaluating finasteride use in women. We know it is not permitted in pregnant women. Risks include birth defects such as developmental abnormalities of the external genitalia in male fetuses if it is used during pregnancy. This medication falls into category X in pregnancy that means it absolutely should not be taken by pregnant women. Finasteride can be absorbed through the skin therefore women should not be permitted to handle finasteride tablets.

To learn more about finasteride, visit our finasteride FAQ page.

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